E F F E C T S O F T E S T I N G A N D E N A C T M E N T O N

M E M O R Y

Veit Kubik

Doctoral Thesis in Psychology at Stockholm University, Sweden 2014

Effects of Testing and Enactment on

Memory

Veit Kubik

©Veit Kubik, Stockholm 2014 Cover illustration by Artin Arshamian ISBN 978-91-7447-993-5 Printed in Sweden by US-AB, Stockholm 2014 Distributor: The Department of Psychology, Stockholm University

“We shall not cease from exploration

And the end of all our exploring

Will be to arrive where we started

And know the place for the first time.”

T. S. Eliot

To: Move On

Abstract

Learning occurs not only when we encode information but also when we test

our memory for this information at a later time. In three empirical studies, I

investigated the individual and combined effects of interleaved testing (via

repeated rounds of study and test practice) and encoding (via motor enact-

ment) during learning on later cued-recall performance for action phrases.

Such materials (e.g., “water the flowers”) contain a verb and a noun and ap-

proximate everyday memory that typically revolves around past and future

actions. Study I demonstrated that both interleaved testing (vs. study only) and

enactment (vs. verbal encoding) individually reduced the forgetting rate over

a period of 1 week, but these effects were nonadditive. That is, the direct test-

ing effect on the forgetting rate occurred for verbal, but not for enactive en-

coding; enactment reduced the forgetting rate for the study-only condition, but

not for the study–test condition. A possible explanation of these findings is

that both study techniques sufficiently elicit verb–noun relational processing

that cannot be increased further by combining them. In Studies II and III, I

replicated these testing-effect results and investigated whether they varied as

a function of recall type (i.e., noun-cued recall of verbs and verb-cued recall

of nouns). For verbal encoding (Study II), the direct testing effect was of sim-

ilar size for both noun- and verb-cued recall. For enactive encoding, the direct

testing effect was lacking irrespective of recall type. In addition, interleaved

tests enhanced subsequent re-encoding of action phrases, leading to an accel-

erated learning. This indirect testing effect was increased for the noun-cued

recall of verbs—for both verbal and enactive encoding. A possible explanation

is that because nouns are semantically more stable, in that the meaning of

nouns changes less over time and across different contexts, they are more rec-

ognizable. Hence, associated information (e.g., about the recall status) may be

more available to the learner during restudy that, in turn, can initiate more

effective re-encoding. The two different testing benefits (i.e., direct and indi-

rect) may, partly, engage different mechanisms, as they were influenced dif-

ferentially by the manipulations of encoding type and recall type. The findings

presented in the thesis provide new knowledge regarding the combined effects

of strategies and materials that influence memory.

Keywords: testing effect, test-potentiated learning, enactment effect, cued re-

call, forgetting, episodic memory

Svensk Sammanfattning

Vi lär oss inte bara genom instudering, utan även när vi efter instuderingen

testar hur väl vi lärt oss något, vilket ofta benämns som testeffekten. Om det

är handlingar vi ska komma ihåg (t.ex. ”vattna blommorna”), så lär vi oss

också bättre genom att utföra handlingarna motoriskt jämfört med att bara läsa

en beskrivning av dem. I tre empiriska studier har jag undersökt hur upprepade

studie- och testtillfällen (jämfört med enbart instudering utan minnestestning),

samt hur motorisk inkodning (jämfört med endast verbal inkodning) påverkar

lärandet och hur väl man minns informationen efter en vecka.

Instuderingsmaterialet bestod av olika handlingsfraser, som exempelvis

”vattna blommorna”, då vardagligt minne ofta involverar förflutna och

framtida handlingar. Studie I visade att både minnestestning, såväl som att

motoriskt utföra en handling ledde till minskad glömska sett över en veckas

tid, men att de två effekterna var icke-additiva (d.v.s. man kom inte ihåg

materialet bättre genom att kombinera minnestestning med motorisk

inkodning). Den positiva inverkan som minnestestning under inlärningsfasen

hade på hur väl deltagarna mindes handlingsfraserna efter en vecka uppstod

dock enbart när fraserna lärts in verbalt, inte när de lärts in genom motoriskt

utförande. En möjlig förklaring till varför de två studieteknikerna i

kombination inte ledde till en additiv effekt kan vara att båda studieteknikerna

involverar samma minnesmekanism, så kallat relationellt processande mellan

verbet och substantivet i en fras. I studie II och III bekräftade jag resultaten

från den första studien i termer av testeffekten (d.v.s. testeffekten uppstod

endast för verbalt inkodat material, inte för motoriskt utförda handlingar), och

undersökte om effekten berodde på vilken ledtråd som gavs vid minnestesten.

Deltagarna fick antingen substantivet som ledtråd för att plocka fram verbet,

eller så fick de verbet som ledtråd för att plocka fram substantivet. När

fraserna lärts in verbalt (Studie II) var testeffekten lika stor oavsett om

ledtråden var ett verb eller ett substantiv. Efter motorisk inkodning uteblev

testeffekten oberoende av vilken ledtråd som gavs vid minnestesten (Studie

III). Testning kan förutom att påverka hur väl man minns efter ett längre

retentionsintervall (t.ex. en vecka) också förbättra inkodningen av information

under senare inlärningstillfällen. I både Studie II och III så lärde sig deltagarna

fler nya ord vid ett ytterligare inkodningstillfälle efter att ha genomgått ett

minnestest med substantivet som ledtråd (”?–blommorna”), jämfört med när

verbet var ledtråd (”vattna–?”). Sammanfattningsvis visar jag i avhandlingen

att minnestestning leder till minskad glömska i samma utsträckning som

motorisk inkodning. Vidare leder minnestestning under inlärningsfasen till att

man vid ett efterföljande studietillfälle lär sig orden bättre och då speciellt de

man inte tidigare kom ihåg. De två effekterna som testning har kan delvis

hänföras till olika mekanismer, eftersom de påverkas på olika sätt av

inkodnings- och framplockningsformatet.

Acknowledgments

The time during my PhD at Stockholm University has been an exciting and

humbling experience. It was with great enthusiasm that I started my little re-

search projects, with the aim to learn as much as possible about memory (and

beyond). Indeed, in the last few years, I learned a lot about memory, and man-

aged to conduct quite a number of experiments. Though, rather than arriving

at ultimate answers to my research questions, ideas of reformulating or ad-

dressing them differently entered my mind. Time has passed quickly (which

is a good sign ) and commanded to the completion of my thesis. Time to

move on.

Throughout this academic journey, I have had the privilege of pursuing, shar-

ing and discussing my research interests with many bright and enthusiastic

people. They have not only helped me sharpen and test my research ideas, but

also to broaden my views and knowledge on many topics outside of my doc-

toral theme(s). While receiving such valuable guidance, I have had the pleas-

ure of enjoying a great deal of freedom, as I was able to choose my own

topic(s) of interest, the people to engage in research with and to travel the

world hunting for the important conferences in my field. These experiences

have really made my PhD experience and have enabled me to learn more than

my thesis has revealed.

First and foremost, I would like to thank my supervisors.

You, Lars-Göran Nilsson, are primarily responsible for me having pursued

my PhD in Stockholm—“the city with the most beautiful university campus

on the world” (these were your words when you welcomed me here for the

first time :). Yes, indeed! I am truly grateful for your help, your patience (with

the long and always returning manuscripts) and for your belief in me becom-

ing a good scientist. You set a very high standard with your work ethic (being

“an early bird”), your devotion to science and yet at the same time being so

humble and gentle. You inspired me with your work, for instance on the en-

actment effect, which is one part of this thesis, and you encouraged me to get

to know the researchers in my field and to collaborate with them. I did! I have

gained and learned a lot from you throughout many discussions over the past

few years! Thank you for your encouraging and sensible words in moments

when I was doubtful and when my research became frustrating. You have con-

tributed greatly in making me a more independent and better researcher.

Fredrik Jönsson, you have been a heavy influence and a great inspiration

to me. I learned many aspects of research from you and you set many stand-

ards that made me a better researcher (yes, also to communicate my ideas a

bit more reader-oriented ;) I am grateful that you integrated me into your new

research group and I have wonderful memories of our conference visits in San

Sebastian and Budapest! It is fair to say that my (later) interest and enthusiasm

for the testing effect and also for metacognition originated from you. In count-

less emails, conversations and meetings, we discussed the latest papers, our

own research and of course better and new future experiments (which I always

end up running regardless/because of the time limitations, as you may have

noticed ;). These discussions were one of the most giving and fulfilling re-

search times during my PhD and fulfilled the reason why I am doing science.

These discussions were the starting point of a thrilling, obsessive research and

travel “trip” in search for further enlightenment. We still have some scientific

“leftovers” from this trip; let’s get them out ! Despite your increasing work-

ing load, you have always been available and a reliable source of support and

advice (“What do you think?!” ;)).

Jonas Olofsson, I vividly remember when you defended your PhD in Umeå

and now it is my turn to finish mine—with you as one of my supervisors. How

cool is that (!) and what moving journey this has been in between! I am grate-

ful for your contributions on my manuscripts. You helped me very efficiently

to further improve my writing in a short time, to set priorities and to focus on

ONE good story. You are the master! Your positive and pragmatic view on

science taught me for sure the one or the other lesson and I enjoyed many good

discussions about important topics in science, life and MMA. Looking for-

ward to more lunch sessions in Kräftriket, more UFC-evenings and continued

collaboration!

Monika Knopf, I am deeply indebted to you for your support throughout

these years. I do remember clearly when you asked me for a meeting in the

second term in order to tell me, convincingly, that I should pursue a scientific

career and that you wanted to put me on the “scientific track.” Since then, I

have been following this track with pleasure and addiction. Although there is

a great deal to say about your academic influence, I want to thank you here

more for all the doors that you have pointed to and even opened for me. Based

on your suggestion, I received the scholarship of the German National Aca-

demic Foundation as an undergraduate and PhD student, and therefore I had

the opportunity to attend “doctoral forums,” “Sommerakademien,” and many

more events, where I made good, inspiring friends. You also encouraged me

to study abroad and to start research already as a student in Brighton and

Stockholm, this is where I got to know Jenny Rusted, Reza Kormi-Nouri and

Lars-Göran Nilsson—all fabulous people who became close to me. Beyond

the specific support of projects or papers, you always emphasized the devel-

opment of my own views and to grow as an independent, self-confident person

in science. This is what I have appreciated most! Despite travelling a lot and

finally doing my PhD in Stockholm, I have ALWAYS been more than wel-

come in your lab in Frankfurt and, in fact, being part of it. A special thank and

greeting to the whole group, which includes, Sven, Isy, Frauke, Jantina, Gabi,

Thorsten, Sonja, Christian, Monika, Margit and Frau Weyershäuser. You all

are important that I feel very happy being at my other academic home!

Thanks!

Thank you for very valuable comments and suggestions on the kappa to Timo

Mäntylä and Linus Holm, and during my half-time seminar again to Timo

Mäntylä and also to Stefan Wiens! You all improved my work to the better!

My gratitude also to Hedvig Söderlund and Jenny Rusted for stimulating dis-

cussion and for being such engaged and positive co-authors.

During my doctoral time, I had the opportunity to visit well-known experts in

my field: Simon Farrell in Bristol and Robert Bjork (and Nick Soderstrom) in

Los Angeles. They all welcomed me to their research laboratories and I so-

phisticated and broadened my views on learning and memory a great deal.

These were one of the prime times of my PhD! Also a special thank you to

Lars Nyberg, Bernt Jonsson and Linnea Karlsson in Umeå, to Henry L. Roedi-

ger and John Nestojko in St. Louis as well as Melanie Steffens and Janette

Schult in Jena, whom I had the opportunity to present and discuss various

research topics with.

Throughout my time in Stockholm, I have had the great privilege to discuss

and/or collaborate with many other researchers who have directly or indirectly

contributed to my thesis: Hedvig Söderlund, Jenny Rusted, Nick Soderstrom,

Andreas Jemstedt, Sven Obermeyer, Stefan Wiens, Gesa van den Broek, Artin

Arshamian, Reza Kormi-Nouri, Maria Sandgren, Sverker Sikström, Wolfgang

Mack, Timo Mäntylä, Tina Faust, Tanja Schatz, Petter Marklund, Eva Nei-

dhardt, John Nestojko, Alan Castel, Kou Murayama, Elizabeth L. Bjork, Ivo

Todorov, Viktoriya Voloshyna, Marc Borner, Karin Schermelleh-Engel,

Helfried Moosbrugger, Anders Sand, Constanze Eib, Max Larsson Sundqvist,

Mats Nilsson, Stina Cornell Kärnekull, Ola Svensson, and Åke Wahlin.

Thank you to the German National Academic Foundation (Studienstiftung des

deutschenVolkes) for granting me an “academic” stipend during my doctoral

time. This allowed me to participate in many doctoral forums and to get to

know many doctoral students and their multidisciplinary projects over a pe-

riod of three years. I had amazing times with you guys from the “Werkstatt”

(Bea, Stefan, Manuel and Susanne), with you Marc, Johannes, Michael, Chris-

toph, Marion, Eric, Maria, Adrian, Thomas, Steffis, Tobias, and so many

more. I am happy to have gained you as friends.

I am more than blessed to have good friends and colleagues in my life, who

made this journey worthwhile and provided me with superb times and needed

distractions. It is impossible to acknowledge each of you. I am glad to have

you—Thomas, Undra, Nico, Johannes, Nat, David, Simon, Bea, Kristina,

Stina, Anne, Ivo, Anders, Tine, Andreas, Henni, Kiki, Shara, Levke, Henrik,

Tina, Geoffrey, Jelena, Stephanie F., Daniel, Matthea, Nathalie, Maria L., Ma-

ria Ö., Johanna S., Stina, Tonya, Stina, Tonya, Ann-Sofie, Ann-Charlotte,

Cilla, Gabriella, Max, Håkan A., Håkan F., Jelena, Jesper, Joakim, Jonas P.,

Kristina, Margaretha, Maria S., Martin, Nischel, Pehr, and Ola Sternäng. Spe-

cial thanks to Artin and Consti for just being such stimulating, loyal, helpful

and fun friends during my doctoral time. Aram, my friend, we had some good

times together! I am glad to have had the best office mates I can imagine, Joao

and Maryam, I have too many funny stories in my memory from you two

Sven—We had great times in Frankfurt and Toronto and shared the highs and

lows in very good company! Thanks Wolfgang and Eva for a superb time in

Wien and many interesting and thought-provoking discussions throughout the

years!

Thank you to Lotta Lindqvist, Camilla Nelson, Monika Karlsson, Tommy

Olin, Henric Bergqvist, Henrik Dunér, Eva Sjöqvist, Eva Persdotter and

Stefan Sanderhem for all your help regarding administrative and IT matters.

I am indebted to my stimulating second working and living room, the café

Ritorno and its fun personnel! “A cappuccino and a cheesecake, please!”

And finally all my gratitude belongs to my family! I am truly blessed having

you, Nikolaj, my smarter alter ego. Having you on this planet, gives me hope,

strength and comfort! Nobody has the tools as you to make me a better person.

Your honesty, insane energy, and endless willingness to help (if I need it)

drives me (at times) nuts! Mama, you are simply the best. Thank you for mak-

ing the journey into the world of science and research possible for me in many

ways (!) and encouraging me to do my (doctoral) studies abroad and to go my

way. Your support and curiosity to see life through my eyes and thoughts over

all these years makes me feel loved. The just so marvelous and humorous

mails helped me “to keep a stiff upper lip”, as you used to say, and kept me

going, often with a smile even in difficult times. Papa, you have surely passed

on some of your overwhelming curiosity, energy and your explorative mind

to me: “Immer strebe nach dem Ganzem.” Carmilotta, my little niece with

only 11 months old, you managed to make me laugh and wonder in moments

when it seemed impossible. You are magic!

List of studies

The present doctoral thesis is based on the following studies:

I. Kubik, V., Söderlund, H., Nilsson, L.-G., & Jönsson, F. U. (2014).

Individual and combined effects of enactment and testing on memory

for action phrases. Experimental Psychology. Advance online publi-

cation. DOI: 10.1027/1618-3169/a000254 *

II. Kubik, V., Nilsson, L.-G., Olofsson, J. K., & Jönsson, F. U. (2014b).

Testing effects on subsequent restudy and forgetting of action

phrases. Manuscript submitted for publication.

III. Kubik, V., Nilsson, L.-G., Olofsson, J. K., & Jönsson, F. U. (2014a).

Putting action memory to the test: Testing affects subsequent restudy

but not long-term forgetting of action events. Manuscript submitted

for publication.

* Used by permission from Experimental Psychology, accepted for publi-

cation 2014 © 2014 Hogrefe Publishing, www.hogrefe.com.

Contents

Introduction .................................................................................................. 1

Memory .......................................................................................................... 3 Memory Classifications ............................................................................................. 3 What is Remembering? ............................................................................................ 5

Concept of Episodic Memory ......................................................................... 5 Three Stages of Remembering and Forgetting ......................................... 7 Encoding and Retrieval Factors .................................................................... 8 Remembering Action Events ....................................................................... 10

How Does Testing Affect Memory? ........................................................ 11 Direct and Indirect Testing Effects ....................................................................... 12

Direct Testing Effect ..................................................................................... 12 Indirect Testing Effect .................................................................................. 13 Additional Testing Effects ............................................................................ 15

Explanations of the Testing Effects ...................................................................... 17 Direct Testing Effect ..................................................................................... 17 Indirect Testing Effect .................................................................................. 21

How Does Motor Enactment Affect Memory? ...................................... 24 Enactment Effect ..................................................................................................... 24 Explanations of the Enactment Effect .................................................................. 26 Theoretical Questions ............................................................................................. 28

Item-Specific versus Relational Processing.............................................. 28 Conceptual versus Motoric Elaboration ..................................................... 30 Automatic versus Strategic Processing ..................................................... 31

Methodological Considerations .............................................................................. 32

Background, Research Objectives, and Methods of Studies ............ 34 Background ............................................................................................................... 34 Research Objectives................................................................................................ 37 Methods of Studies .................................................................................................. 38

Overview of Studies .................................................................................. 40 Study I....................................................................................................................... 40

Objective ........................................................................................................ 40 Background .................................................................................................... 40 Method ............................................................................................................ 41 Results ............................................................................................................ 42 Conclusions .................................................................................................... 43

Study II ..................................................................................................................... 44 Objective ........................................................................................................ 44 Background .................................................................................................... 44 Method ............................................................................................................ 44 Results ............................................................................................................ 45

Conclusions .................................................................................................... 47 Study III.................................................................................................................... 49

Objective ........................................................................................................ 49 Background .................................................................................................... 49 Method ............................................................................................................ 49 Results ............................................................................................................ 50 Conclusions .................................................................................................... 52

General Discussion .................................................................................... 53 Testing Effects ......................................................................................................... 53

Direct Testing Effect ..................................................................................... 53 Indirect Testing Effect .................................................................................. 55

Enactment Effect ..................................................................................................... 57 Alternative Memory-Strength Explanation .......................................................... 60

Challenges and Directions for Future Research .................................. 62 Methodological Challenges ..................................................................................... 62

Isolating Direct and Indirect Testing Effects ............................................ 62 Measuring Forgetting ................................................................................... 65 Action Phrases—Asymmetric Learning Material ...................................... 67

Theoretical Challenges ........................................................................................... 68 Multiple Implementations of Testing ......................................................... 68 A Synthesis—An Item–Context Account ................................................... 69

Practical Challenges ................................................................................................ 72

Concluding Remarks ................................................................................. 74

1

Introduction

We often view learning as the process of taking in new information. To im-

prove our learning outcomes, we focus on optimizing the encoding of infor-

mation. For example, we may develop visual images or read the to-be-learned

information aloud. Both study techniques typically result in better memory

performance than silent reading (MacLeod et al., 2010; Paivio, 1971). From

this traditional perspective, testing memory serves mainly to measure the de-

gree of learning associated with different encoding techniques. However, re-

trieving information from memory is not neutral for learning. Contrary to our

everyday intuitions, retrieval can promote learning. Each successful retrieval

changes the retrieved information in memory and enhances its recallability in

the future. This phenomenon is supported by recent evidence on the so-called

testing effect. Tests during learning facilitate subsequent re-encoding and re-

duce the rate at which people forget information, relative to simple restudy of

the materials (Pyc, Agarwal, & Roediger, 2014; Roediger & Butler, 2011).

Thus, testing does not only assess learning, it is an effective tool to enhance

it.

In addition, we usually view memory as a place where the encoded infor-

mation is stored—similar to a “storehouse” of input elements (Koriat & Gold-

smith, 1996). In this sense, memory is often investigated in experimental sit-

uations, in which learners passively observe a list of words or word pairs that

are presented to them. However, in everyday life people are actively involved

in events and have to remember actions that they have recently performed or

will need to perform. For example, before leaving your flat, you need to re-

member whether you turned off the oven and closed the windows (past ac-

tions) or that you need to buy medicine after lunch (future obligation). This

primacy of memory for actions in daily life reveals, for example, in superior

recall for enacted information. Research demonstrated that motorically per-

forming action phrases (e.g., “water the flowers”) during encoding typically

trumps any form of verbal encoding in enhancing later retention, in the so-

called enactment effect (for reviews, see Zaromb & Roediger, 2010; Zimmer

et al., 2001). It is possible that human memory has evolved over time in such

a way that our ability to keep action-relevant information in mind has im-

proved (Glenberg, 1997; Ratner & Foley, 2001). To understand the nature of

human learning and memory, it is important to consider the active role of re-

trieval and the primacy of actions for everyday memory.

2

The overall aim of this thesis is to contribute to the understanding of how

retrieval and encoding can support human learning and memory of actions.

Both study techniques have the potential to be more systematically incorpo-

rated into educational practice and used as effective learning tools that lead to

durable and flexible knowledge. The present thesis has two general objectives.

The first objective is to evaluate the effects of interleaved testing (i.e., repeated

study–test practice) with more ecologically valid learning material. In the

studies included in the present thesis, I used action phrases (e.g., “water the

flowers”) to investigate memory through realistic learning materials that

mimic the basic actions required in everyday life. Testing effects have been

observed across various learning materials (e.g., word pairs and test passages).

However, they have not been investigated with action-related information,

even though everyday memory is highly concerned with such information.

The second objective is to investigate the relative and combined efficacy of

interleaved testing and motor enactment on learning and retention. Both re-

trieval via testing and enactment facilitate later retention of information and

have generated a great deal of attention (cf., Roediger & Butler, 2011; Roedi-

ger & Zaromb, 2010). However, little is known about their joint effects. Do

both study techniques have additive effects when they are combined or do they

interact to produce nonadditive effects? Additive effects would suggest that

both study techniques rely on independent mechanisms, while nonadditive ef-

fects would suggest that they rely in parts on the same mechanism(s).

In the following sections, I first present an overview of the conception and

classification of human memory with an emphasis on episodic memory, since

this is the main memory system addressed in the thesis. Then, I introduce the

facilitative effects of testing and enactment on episodic memory. Next, I turn

to the empirical part of this thesis and provide a brief overview of its three

empirical studies. Finally, I discuss the findings from these studies in the con-

text of current theoretical accounts and suggest potential avenues for future

research.

3

Memory

The modern investigation of human memory falls short of providing a precise,

general definition of its object of investigation (Tulving, 1983), perhaps with

good reason. Attempting to account for all memory-related phenomena leaves

us with a very broad definition of memory, along the lines of “the representa-

tion of past experiences that exists over time” (Schacter, 2007, p. 25). Tulving

(1983) emphasized that an effective definition of memory should be more

comprehensive than simply the storage of information and should also pertain

to encoding and retrieval processes. For example, in cases of retrieval failure,

one would neither speak of memory nor conclude that there is no memory for

a particular information. Instead, it may be that the encoded information is in

storage, but it simply cannot be retrieved (i.e., it is not accessible at the present

time), as the appropriate retrieval cues may not be present (Tulving & Pearl-

stone, 1966). Thus, encoding, storage, and retrieval together interactively con-

tribute to what constitutes memory (Schacter, 1996). To separate the individ-

ual contributions of these memory constituents is a challenge in contemporary

research (cf. Schacter, 2007).

Memory Classifications

There are two major cognitive approaches to understand human memory—

system-oriented and process-oriented approaches. The system-oriented ap-

proach views human memory not as a single entity but as being composed of

multiple functionally and biologically distinguishable subsystems (Squire,

2004). Depending on the researchers’ focus, different classification systems

have been developed, varying along the time dimension (sensory memory,

short-term memory, and long-term memory), content and state of awareness

(procedural vs. declarative memory and episodic vs. semantic memory), or

other criteria. Although the exact number of systems is a matter of ongoing

debate and their nature is rather hypothetical, the system-oriented approach

provides a useful framework to integrate and discuss findings on human

memory.

4

Many contemporary researchers agree that memory can be divided into five

interrelated memory systems, that is, primary memory, episodic memory, se-

mantic memory, the perceptual representation system, and procedural

memory (Nyberg & Tulving, 1996; Tulving, 1983, 1985, 1993). Primary

memory (also referred to as working memory) enables us to retain incoming

information for relatively short time periods and to process it. Episodic

memory refers to the conscious recollection of personally experienced infor-

mation or events that occurred at a specific time and place. It captures aspects

related to the “what,” “when,” and “where” of information (Nyberg et al.,

1996). Semantic memory permits the implicit retrieval of general, decontextu-

alized knowledge of concepts (e.g., the meaning of words) and facts about the

world (e.g., the capital of Sweden). The perceptual representation system

mainly permits rapid identification of formerly encountered perceptual stim-

uli, and procedural memory is concerned with the acquisition and retention of

behavioral skills or procedures. These memory types are presumed to have

evolved sequentially—both across the phylo- and ontogenesis—, with proce-

dural memory developing earliest and episodic memory developing last. Fur-

thermore, these memory systems are associated with different states of aware-

ness (Tulving, 1993, 2002). Episodic memory allows the conscious recollec-

tion of previously occurred events from a specific episode (i.e., autonoetic

awareness). Retrieval from semantic memory, however, is implicit1 and is ac-

companied by feelings of familiarity or knowing (i.e., noetic awareness). Re-

trieval from primary memory is associated with a fleeting awareness of

thoughts and perceptions, as long as we consciously attend to them. In contrast

to these later developing memory systems, retrieval from the perceptual rep-

resentation system and procedural memory lack any form of conscious aware-

ness.

As episodic and semantic memory are most directly relevant to the present

thesis, it should also be noted that they have been classified as the two declar-

ative forms of long-term memory (in contrast to the nondeclarative forms of

procedural memory and priming). Both facts and events stored over long time

spans (i.e., years or even decades) can be deliberately recalled and verbally

expressed (Squire, Knowlton, & Musen, 1993). Though, based on several

findings, episodic and semantic memory should be viewed as separate sys-

tems. For example, some brain-damaged patients suffering from brain damage

exhibit specific deficits in episodic memory, but not in semantic memory

(Vargha-Khadem et al., 1997); the two memory systems involve in parts dif-

ferent brain areas (Cabeza & Nyberg, 2000), and episodic memory has been

1 Retrieval from semantic memory (e.g., “Is Stockholm the capital of Sweden?”) can be viewed

as implicit in the specific sense that learners do not deliberately attempt to retrieve information

from a specific episode and that they do not consciously recollect the specific episode. However,

semantic retrieval can be also viewed as “explicit” in the sense that learners can voluntarily

retrieve previously acquired knowledge and be aware of it (Tulving, 2000).

5

shown to decline earlier in the life span (Rönnlund, Nyberg, Bäckman, & Nils-

son, 2005).

The process-oriented approach views memory as one aspect of the general

cognitive system (Craik, 2007) that is produced by perceiving, understanding,

and acting upon the world (Craik, 2002; Craik & Lockhart, 1972; Craik &

Tulving, 1975). Memory is regarded as a mental activity that is best analyzed

in terms of the encoding and retrieval processes involved in specific memory

tasks. Encoding processes, on one hand, are presumed to vary in depth of pro-

cessing, with deeper, semantic processing leading to better memory perfor-

mance (on explicit memory tests) than shallower, phonological processing.

This is referred to as the levels-of-processing effect (Craik & Tulving, 1975).

Retrieval processes, on the other hand, increase memory performance to the

extent that they recapitulate the initial encoding processes and cues; this is

called the encoding-specificity principle (Tulving & Thomson, 1973). For ex-

ample, the semantic processing of information increases memory performance

on those tests that tap on semantic information (e.g., recall and recognition

tests), and thus encoding processes benefit later memory performance only if

they can be transferred appropriately to the test at retrieval (this is referred to

as the transfer-appropriate processing principle; see Morris, Bransford, &

Franks, 1977). From this process-oriented approach, it is not necessary to as-

sume specific memory stores.

The two approaches—one delineating the structure of memory, the other

modeling the underlying processes invoked in the various memory tasks—

complement each other and contribute to the understanding of human

memory. One contemporary trend is to integrate both approaches in so-called

process-oriented systems.

The present thesis does not strictly adopt one or the other of these ap-

proaches but, rather, relates to both of them. On one hand, I refer to various

processing accounts, such as item-specific and relational processing, to ex-

plain the results pattern of the testing and enactment effects on cued recall. On

the other hand, I assume that the studies of list learning included in the present

thesis tap episodic memory (Kahana, Howard, & Polyn, 2008; Tulving, 1972),

although other memory systems, most notably semantic memory, are also

likely to be involved.

What is Remembering?

Concept of Episodic Memory

Episodic memory refers to the capability to remember information or events

that occurred at a specific place and time. Critically, not only the information

per se is remembered but also information associated with it, such as the sur-

rounding temporal, spatial, or social context (i.e., when, where, and with

6

whom; see Yonelinas, 2007). The query “What did you do last weekend?” or

“Can you recall the words that I presented to you a week ago and write them

down?” requires episodic memory. It enables the learner to travel back in time

(Tulving, 1983, 2002) and to re-experience events of one’s personal past. Ep-

isodic memory can be directed not only back toward the past but also toward

the future (Schacter & Addis, 2007), as it enables the learner to travel forward

and “pre-experience” himself or herself in a novel situation (i.e., episodic fu-

ture thinking; for a review, see Szpunar, 2010). A critical feature of episodic

memory is that it is associated with autonoetic consciousness (Tulving, 1985,

2001), that is, the self-awareness that it is me who is remembering my own

past or thinking about my own future. Another less discussed feature is that

remembering involves a judgment that the retrieved information is a memory

of a specific event (Yonelinas, 2007).

Episodic memory is related to autobiographical memory, though the two

concepts can be distinguished. Autobiographical memory comprises self-

knowledge (e.g., knowing that one can work well under pressure), episodic

memories related to self-knowledge (e.g., remembering the sunrise that oc-

curred when one was preparing for the philosophy exam early in the morning),

and also facts from semantic memory (e.g., schematic knowledge about an

exam). Critically, all these different types of information (self-knowledge, ep-

isodes, facts, and procedures) are related to the self and to one’s personal his-

tory. As autobiographical memory is a more comprehensive concept than ep-

isodic memory (Conway, 2001; cf. Roediger & Marsh, 2003), it engages ad-

ditional brain regions beyond those typically engaged in episodic memory

(Cabeza et al., 2004) and is studied using separate methods (e.g., diary studies

and the event-cuing technique; see Roediger & Marsh, 2003).

In the included studies of this thesis, participants learned a list of action

phrases (verb–noun phrases, such as “water the flowers”) and memory was

assessed by a cued-recall test (i.e., one item was given and the participant was

asked to recall the other). This form of testing required them to retrieve parts

of the previously encoded item pair and the formed associations between

them, which are typical features of episodic memory. However, other features

of episodic memory, such as the location or the recollective experience, were

not assessed. This list-learning paradigm taps specific aspects of episodic

memory but less specific aspects of autobiographical memory, as the learned

action phrases are likely not relevant in terms of self-knowledge and personal

history, although action events have been argued to be more self-involving

(Kormi-Nouri & Nilsson, 2001). It should be acknowledged that semantic

memory may contribute to successful recall in such situations; encoding re-

quires the participants to understand the meaning of the action-phrase material

and recall performance is also influenced by pre-experimental, semantic asso-

ciations between items—that is, by prior knowledge (Tulving, 2002). Thus, it

is possible that episodic and semantic memory interact in typical list-learning

experiments, as they can be regarded as parallel and partially overlapping in-

formation processing systems within long-term memory (Tulving, 1972).

7

Three Stages of Remembering and Forgetting

Most studies assess episodic memory by means of so-called list-learning ex-

periments, in which subjects learn a series of independent items. The proce-

dure of these experiments can be divided into three stages (McDermott, 2007):

encoding (i.e., acquisition), storage (i.e., retention), and retrieval (i.e., access

to or reconstruction) of information. For example, you may be asked to learn

20 action phrases such as “lift the glass” (i.e., the encoding stage). After a

given time period, perhaps one week (the retention or storage stage), the verb

from each phrase (“lift”) is presented as a cue and you are asked to recall the

noun (“the glass”); this cued recall test constitutes the retrieval stage. Alterna-

tively, more demanding recall tasks could be presented, such as requiring you

to retrieve all the action phrases freely in any order (i.e., free recall) or in the

original order of study (i.e., serial recall). Or you may be presented with a list

of action phrases and asked to indicate which ones were previously presented

during encoding and which were not (i.e., a yes–no recognition test; for a

methodological and theoretical description of these tests, see Kahana, 2012).

Although these tests do not solely tap episodic memory, they assess at least

one critical aspect of it, as the subject needs to deliberatively retrieve the in-

formation provided at a specific time (and also at a specific location if the to-

be-remembered events happen outside the laboratory context). To further dis-

tinguish episodic memory’s contributions from those of semantic memory,

you may be asked to describe his or her subjective status of awareness—for

example, by additionally indicating whether the recognition decisions origi-

nated from remembering the item’s presentation or simply from knowing that

it was presented (Gardiner, 1988; Tulving, 1985).

All these types of episodic memory tests demonstrate that successful re-

membering requires passing through the stages of encoding, storage, and re-

trieval. Let us assume that you have successfully recalled 12 out of 20 nouns.

To remember each of these 12 nouns, you needed to encode, store, and con-

solidate them in long-term retention, as well as to successfully retrieve them

after 1 week when prompted with the verb cues. However, what can be said

about the eight forgotten nouns? One possibility is that the memory trace had

been completely erased from your storage. Irrespective of the retrieval condi-

tions, you cannot retrieve these nouns any more. However, this scenario is a

rather implausible one, except perhaps in extreme forms of dementia (Davis,

2007). More likely, your inability to recall these forgotten items is evidence

of retrieval failure, although the underlying cause may be related to any of the

three stages. Perhaps these action phrases, after being briefly held in working

memory, were simply not stored in long-term memory (i.e., an encoding fail-

ure). Alternatively, a memory trace of an event may have been stored in long-

term memory, but its strength has decayed over time (McGeoch, 1932), so that

the trace is still available but no longer accessible (Tulving & Pearlstone,

8

1966). A third possibility is that the memory trace is still available and acces-

sible but that the retrieval cues have temporarily failed to elicit retrieval; in

this instance, the memory may be retrievable at a later time or under stronger

cuing conditions (i.e., cue-dependent forgetting; see Tulving, 1974). As an il-

lustration of this possibility, perhaps you may not be able to recall the nouns,

but when you are given a recognition test of previously studied and new target

items, you may still recognize the “forgotten” nouns as items that you learned

previously (Tulving & Pearlstone, 1966).

This example suggests that forgetting and remembering may be seen as two

sides of the same coin: successful remembering reveals when forgetting does

not occur, and forgetting reveals when retrieval fails. However, such a defini-

tion turns out to be inaccurate when we consider the process of forgetting over

time. Long-term forgetting of information can be accurately assessed only if

the memory has been successfully encoded into long-term memory, and the

same retrieval cue is given repeatedly across retention intervals (RIs). For this

reason, in the present studies, memory was also assessed immediately after

the learning phase to determine the baseline level of retrieval success and

thereby to investigate the degree to which previously retrieved information

subsequently becomes unretrievable (i.e., the retention curves). In this way,

forgetting can be more precisely defined as the “inability to retrieve infor-

mation that was once consciously accessible under the cuing conditions that

are again in effect now” (Wixted, 2007, p. 330). This modified definition turns

forgetting and remembering into dependent rather than opposing concepts. Ei-

ther way, the study of forgetting is an important approach in investigating ep-

isodic memory.

Many mechanisms have been proposed to explain the empirical phenome-

non of retrieval failure. One explanation revolves around the notion that the

strength of the memory trace decays over time (i.e., decay theory; for a classic

evaluation, see McGeoch, 1932). Another explanation is that forgetting results

from interference by other events, which can stem from previous learning

(proactive interference) or encountering new information (retroactive interfer-

ence). For example, if you want to remember your current bank account num-

ber, you may remember instead the one that you had earlier (proactive inter-

ference). A final explanation suggests that, over time, additional information

becomes associated with a retrieval cue (nown as cue overload theory; see

Watkins & Watkins, 1975. The more the retrieval cue is “overloaded,” the less

effective it becomes in eliciting the retrieval of the specific target information

(this is). As the studies included in this thesis did not attempt to adjudicate

between these theoretical options, I will not evaluate them further.

Encoding and Retrieval Factors

As noted earlier, episodic memory involves encoding, storage, and retrieval

of information. Importantly, these components interact with each other. For

example, encoding of information involves the retrieval of previous events or

9

general knowledge, and the act of retrieval itself can be regarded as an encod-

ing event that changes and probably elaborates the memory of the stored

event.

However, research and educational practices have generally focused on the

encoding side of learning. For example, it has been reliably observed that gen-

erating a word (e.g., “rapid”) from a cue (e.g., “fast–r…”) increases memory

performance compared to just reading that word (the generation effect,

Slamecka & Graf, 1978). Similarly, memory advantages have been demon-

strated when words were pronounced rather than not pronounced (the produc-

tion effect, MacLeod, Gopie, Hourihan, Neary, & Ozubko, 2010) or semanti-

cally processed rather than phonemically processed (the levels-of-processing

effect; Craik & Lockhart, 1972). However, these encoding effects also depend

on the retrieval test given. For example, the generation effect (Bertsch et al.,

2007) and the production effect (Fawcett, 2013) are more pronounced in

recognition than in free-recall. This can be explained by the so-called encod-

ing specificity principle, in that study techniques enhance mainly item-spe-

cific information (i.e., the individual features of items) relative to silent read-

ing, but less so relational information between items (e.g., temporal or seman-

tic associations; Jones & Pyc, 2013; Mulligan & Lozito, 2004). As the recog-

nition test mainly taps item-specific information, both encoding effects are

increased with this memory test as compared to their size in free recall, which

additionally requires inter-item relational information. Thus, the success of

recall depends on the interaction of encoding and retrieval processes.

To complicate things further, the success of learning is not determined only

by the way in which information is encoded into memory and assessed by the

memory tests. The act of retrieval and reconstruction of knowledge from

memory in itself can alter the accessibility of information in memory (Bjork,

1975; Karpicke, 2012). For instance, taking a test on the material to be learned

leads to better long-term retention than simply rereading it, probably because

it reduces the rate of forgetting. The resulting memory advantage for tested

items over (in this example) restudied items is known as the direct testing

effect. However, testing can also have detrimental effects on memory for in-

formation, which is in competition with to-be-recalled information. For exam-

ple, selective retrieval of a subset of studied items can inhibit or interfere with

subsequent retrieval of the other, nonretrieved items. This result memory dis-

advantage is referred to as retrieval-induced forgetting (Anderson, Bjork, &

Bjork, 1994; Storm, Bjork, & Bjork, 2012). Thus, retrieval can induce both

learning and forgetting of information, critically depending on the specific sit-

uation (Bäuml & Schlichting, 2014; Bjork, 1975). Retrieval is a key process

to understand learning (Karpicke, 2012; Tulving, 1991). The present thesis

aims to investigate the impact on memory of action phrases of both a retrieval

manipulation (interleaved testing vs. study-only practice) and an encoding

manipulation (enactive vs. verbal encoding). The focus is set on the positive

testing effects on learning of action-relevant information.

10

Remembering Action Events

Episodic memory is an integral part of our everyday activities. The most basic

actions that we perform in the present are determined by our ability to remem-

ber what we have done in the past and what we intend to do in the future.

However, research on episodic memory often investigates the encoding, re-

tention, and retrieval of verbal material (mostly lists of words or word pairs)

in the laboratory. Participants are thereby often assigned the role of passive

observers who must take in and memorize the input presented to them. Thus,

memory is studied in an experimental situation in which it is supposed to func-

tion like a “storehouse” (Koriat & Goldsmith, 1996) of input elements. In con-

trast, the use of memory in everyday life typically occurs in situations where

the learner is actively involved in events and social interactions. It is not con-

fined to the intake of information, but is also concerned with the “overt (and

covert) (re-) actions as a response to the environmental stimulus” (Zimmer &

Cohen, 2001, p. 4). People have to remember the actions that they have taken

or that they intend to perform at some future point in time. Thus, it can be

argued that the brain’s primary function is to enable actions that promote sur-

vival and reproduction in a changing environment. Human episodic memory

may have been designed partially to keep action-relevant information in mind.

From this perspective, memory research in the early 1980s started to use

action phrases (often verb–noun phrases) as stimulus material and let partici-

pants motorically perform them as a form of enacted learning. These self-per-

formed, simple actions mimic the everyday affordances of memory in a more

realistic way compared with word lists. These simple action phrases (“lift the

glass”) were used as the learning material in the empirical studies included in

this thesis, and they were either motorically performed or read aloud as part

of a single study trial. However, these self-performed actions still do not cap-

ture other aspects of their real-world counterparts, which are more complex,

goal-directed, and of higher personal relevance (Foley & Ratner, 2001). It may

be important to note that retrieving the verbal action phrases primarily

measures episodic memory. Though, procedural memory may also be in-

volved to some extent when one performs or even reads the action phrases

(Cohen, 1989), although it deals mainly with the acquisition and reproduction

of motor skills through intensive practice. Procedural memory is, for example,

assessed with the rotary pursuit task (i.e., tracking a revolving target with

some indicator device).

In the present thesis, I will use action phrases to study the testing effects

on memory for action phrases, both for verbal encoding (Studies I and II) and

for enactive encoding (Studies I and III). In the next section, I will turn to the

effects of retrieval on learning and forgetting, the so-called testing effects (for

reviews, see Roediger & Karpicke, 2006b; Karpicke, Lehman, & Aue, 2014).

Subsequently, I focus on the pervasive encoding phenomenon that has at-

tracted much research, the enactment effect (for reviews, see Nilsson, 2000;

Zaromb & Roediger, 2010; Zimmer et al., 2001).

11

How Does Testing Affect Memory?

“Retrieval from memory is often assumed, implicitly or explicitly, as a

process analogous to the way in which the contents of a memory loca-

tion in a computer are read out, that is, a process that does not, by itself,

modify the state of the retrieved item in memory. In my opinion, how-

ever, there is ample of evidence for a kind of Heisenberg principle with

respect to retrieval processes: an item can seldom, if ever, be retrieved

from memory without modifying the representation of that item in

memory in significant ways.” (Bjork, 1975, p. 123)

In our current educational system, tests and examinations are still primarily

regarded as assessment tools used to measure student learning. Since testing

is seen as fulfilling only this role, it is limited to the minimum necessary in

school classrooms and even at the university level, and it often occurs cumu-

latively at the end of the term or the curricular period (cf. Roediger & Kar-

picke, 2006b).

However, testing is an active learning event that alters the state of memory

(Bjork, 1975). Taking a memory test can enhance learning and long-term re-

tention more than restudying, and these test-related benefits can increase fur-

ther when testing is repeated (Karpicke & Roediger, 2010) or spaced out tem-

porally during learning (Landauer & Bjork, 1978; but see Karpicke & Roedi-

ger, 2010). Nevertheless, the mnemonic influence of tests on learning curves

has been rather neglected, even in action-memory research (Koriat & Pearl-

man-Avnion, 2003; Kubik, Obermeyer, Meier, & Knopf, 2014a, 2014b), de-

spite the fact that test-related benefits on memory are one of the more reliable

phenomena in learning and memory research (Karpicke et al., 2014; Roediger

& Butler, 2011). In the empirical studies of this thesis, I investigate the role of

testing in the frequently used multitrial learning paradigm by adding a study-

only condition, and I extend the positive testing effect to another, ecological

meaningful, action-relevant learning material.

12

Direct and Indirect Testing Effects

Recently, direct and indirect effects of testing have been distinguished and

have received some empirical scrutiny (Arnold & McDermott, 2013b; Kar-

picke et al., 2014; Roediger & Karpicke, 2006b). Although it is difficult to

disambiguate these two types of effects in many experimental situations, it is

important to consider them separately when possible.

Direct Testing Effect

Most research in the last decade has been devoted to the direct effects of test-

ing (or retrieval practice). Direct effects refer to the benefits in (long-term)

learning that accrue from the very act of retrieving information from memory

itself (reviewed in Roediger & Butler, 2011; Roediger & Karpicke, 2006b; for

a meta-analytic review, see Rowland, 2014). These benefits are usually inves-

tigated in an experimental paradigm in which, after an initial study trial, par-

ticipants either attempt to retrieve the learning material in a memory test, res-

tudy the material, or receive no study activity at all. Typically, retrieval prac-

tice enables learned items to be recalled better and over longer time periods

than if one does not engage in retrieval practice or receives complementary

study time (Halamish & Bjork, 2011; Kornell, Bjork, & Garcia, 2011). How-

ever, after shorter RIs, additional restudy trumps retrieval practice (Roediger

& Karpicke, 2006b; Wheeler, Ewers, & Buonnano, 2003). In short, the type

of learning activity utilized by participants in the second trial (retrieval prac-

tice, restudy practice, or no practice) and the RI (short vs. long) interact

(Roediger & Karpicke, 2006b; van den Broek, Takashima, Segers, &

Verhoeven, 2013).

To illustrate this classical testing effect, I provide an example from a study

by Roediger and Karpicke (2006a). They provided participants prose passages

on different topics as learning material and asked the participants to free recall

as many of the idea units as possible after five minutes and again after one

week. The subjects had four experiences each of learning the passages, but in

three different combinations of study (S) and testing (T), i.e., SSSS, SSST,

and STTT. The results demonstrated that final recall performance after the

short RI increased with the number of study trials, whereas long-term reten-

tion increased with the number of test trials. Thus, successfully retrieving

items from memory during learning functions as a “memory enhancer” (Bjork,

1975), in that the future retrievability of these items was enhanced relative to

if one had simply restudied them. This result led to the conclusion that testing

slows the rate of forgetting (Carpenter, Pashler, Wixted, & Vul, 2008;

Wheeler et al., 2003; but for alternative viewpoints, see Halamish & Bjork,

2011; Kornell et al., 2011; Storm, Friedman, Murayama, & Bjork, 2013).

Several factors make reliable contributions to the efficacy of retrieval prac-

tice (Roediger & Butler, 2011). One factor is the number of test events given.

13

The repetition of tests increases the facilitative effects on long-term retention

(Roediger & Karpicke, 2006a). Another factor is the spacing of testing events.

The more widely they are distributed across time—rather than occurring close

to each other, almost as a single event—the more mnemonically efficient they

are (Jacoby, 1978; Landauer & Bjork, 1978; but see Karpicke & Roediger,

2010). Third, the difficulty of successfully retrieving the items to be remem-

bered determines the efficacy of retrieval practice (see Bjork, 1975, who refers

to a level of “desirable difficulty”). Through manipulating the type of memory

assessment used during intermediate test trials, retrieval practice was shown

to have stronger benefits in free-recall tests compared with cognitively less

demanding cued-recall tests or recognition tests (Halamish & Bjork, 2011).

Thus, with increasing difficulty, retrieval becomes mnemonically more effec-

tive. Finally, feedback following each test event provides restudy opportuni-

ties for items that are not successfully recalled and thereby leads to superior

retention after shorter RIs (Kang et al., 2007). However, providing the learner

with such restudy opportunities adds another benefit to learning, the indirect

effect of testing.

Indirect Testing Effect

There has also been a recent surge of interest in the indirect effect of testing,

which is alternatively called test-potentiated learning (Izawa, 1966; Karpicke

& Roediger, 2007). This term refers to the finding that taking tests enhances

subsequent re-encoding of information, specifically when the attempted re-

trieval of information from memory has failed. When items are not recalled

on a test, they are likely to receive more or enhanced encoding during an en-

suing restudy and/or feedback event when the information is presented again.

This, in turn, enhances subsequent memory performance even after relatively

short delays, matching restudy practice in some cases (Nelson, Arnold, Gil-

more, & McDermott, 2013; Vestergren & Nyberg, 2014) and outperforming

it in others (Karpicke, 2009; Pyc & Rawson, 2012). Typically, this indirect

testing effect has been demonstrated by applying a multitrial learning para-

digm in which trials of study trials also follow test trials (e.g., STSTST) as

well as precede them (as is the case when examining the direct effects of test-

ing, such as by using a schedule of SSTT). That is, conditions involving at

least one test–restudy sequence (i.e., initial study, then testing, and then res-

tudy) have been compared to conditions where only restudy occurs after the

initial study trial.

Early studies (Izawa, 1966, 1970, 1971; Lachman & Laughery, 1968)

showed reliably that increasing the number of test trials preceding a restudy

trial leads to a faster learning rate (i.e., steeper learning curves). Izawa (1966,

1970) assumed that no learning (or forgetting) occurs during test trials; she

attributed the accelerated learning rate to test-potentiated learning. That is,

testing facilitates subsequent encoding even when no immediate feedback is

14

provided and the restudy opportunity occurs in a separate trial, with many

other items occurring between them.

However, Arnold and McDermott (2013b) questioned the assumption that

learning does not occur during testing, as recent research has shown reliable

direct effects of testing (see previous section). Consequently, the finding that

learning rates increase with the number of interpolated tests could possibly

originate from both indirect (potentiated) and direct effects of testing. To iso-

late these effects more clearly from each other, Arnold and McDermott

(2013b) differentiated between items that are retained from before (pre-test)

to after (post-test) a restudy trial and items that are newly retrieved. The re-

tained items may reflect direct and indirect effects of testing, whereas the

newly retrieved items possibly reflect the potentiating effects of testing. Based

on this reasoning, they applied a 20-trial cued-recall paradigm to the task of

learning foreign-language vocabulary pairs. Following an initial study trial,

participants received either five tests or one test before restudying the material.

Results revealed that the learning rate was greater for the five-test condition

compared with the one-test condition, thus replicating previous research

(Izawa, 1966, 1971). Importantly, the proportion of newly retrieved items fol-

lowing the first and second restudy trials was greater for the five-test condi-

tion, suggesting that test-potentiated learning increased with the number of

interleaved test trials. As the proportion of retained items after the first restudy

trial was also heightened for the five-test condition, an increased direct testing

effect via successful recall attempts may also have contributed to the acceler-

ated increase in the learning rate with more preceding test trials. Recent evi-

dence indicated that test-potentiated learning might apply not only to unsuc-

cessfully recalled but also to successfully recalled items (Vestergren &

Nyberg, 2014). Irrespective of the previous recall status, tested items (when

compared with ones that were additionally studied) may receive more focused

attention during restudy according to the authors, as indicated by increased

activations in the anterior insula (AI). However, in a behavioral paradigm, the

indirect testing effect can be examined only in terms of new learning of items

not successfully recalled on the pre-restudy test.

Another paradigm was reintroduced (Kornell, Hays, & Bjork, 2009) to ex-

amine the effects of attempted retrieval on subsequent encoding. In this “pre-

test” paradigm (Slamecka & Fevreiski, 1983), participants learned word pairs

in a study trial. Some of the word pairs were “pre-tested” immediately before-

hand by presenting the cue word and letting participants attempt to retrieve

the target word from semantic memory (without successfully generating the

target information). On a subsequent recall test, pre-tested items were better

recalled than ones that were only studied. This result pattern suggests that just

attempting retrieval by itself can facilitate subsequent encoding of the pre-

tested items (Grimaldi & Karpicke, 2012; Hays, Kornell, & Bjork, 2013; Kor-

nell, 2014; Kornell et al., 2009; Wissman, Rawson, & Pyc, 2011). However,

this phenomenon should perhaps be called generation-potentiated learning

(cf. Arnold & McDermott, 2013b), as pre-testing of targets involves generated

15

target guesses retrieved from semantic memory rather than retrieval attempts

from episodic memory. Several findings support this differentiation. For ex-

ample, increasing the delay between the pre-test and study decreases or even

obviates the potentiating effects of pre-tests (Grimaldi & Karpicke, 2012;

Hays et al., 2013, Experiments 1 and 2, but see Experiment 3 for a different

result; Huelser & Metcalfe, 2012; Kornell, 2014), and the pre-test effect was

not observed for weakly related word pairs (Grimaldi & Karpicke, 2012; Hays

et al., 2013; Kornell et al., 2009). However, test-potentiated learning in mul-

titrial learning paradigms facilitates the re-encoding of unrelated items (e.g.,

weakly associated words in Nelson et al., 2013; foreign-language word pairs

in Arnold & McDermott, 2013b; Vestergren & Nyberg, 2014) and pertains to

restudy opportunities that are provided in a separate trial after many other test

events occurring in between (Arnold & McDermott, 2013a, 2013b; Vestergren

& Nyberg, 2014).

In sum, testing is a powerful study technique that can enhance the future

retainability of information through successful retrieval attempts from

memory. Furthermore, it can enhance the impact of subsequent restudy in

terms of learning unsuccessfully retrieved items (Arnold & McDermott,

2013b; Izawa, 1969, 1970) and perhaps also successfully retrieved items

(Vestergren & Nyberg, 2014).

Additional Testing Effects

In addition to the direct and indirect benefits of testing, recent studies have

indicated that testing provides the learner with a multitude of other benefits

when compared with restudying. For example, testing bestows the learner with

a metacognitive benefit. That is, retrieval practice enhances the learner’s abil-

ity to accurately predict his or her own future performance (Nelson & Dun-

losky, 1991; for a review, see Rhodes & Tauber, 2011), presumably because

retrieval practice exposes the gaps in one’s own knowledge. Taking a test en-

ables learners to discover which items they can and cannot remember. Such a

diagnostic retrieval experience guides the learner to select those items that

need the greatest amount of restudy, choose effective learning strategies, and

efficiently allocate the resources of study time and attention (Finn & Metcalfe,

2007; Koriat, Sheffer, & Ma’ayan, 2002; Nelson & Dunlosky, 1991). Testing

apparently also has positive effects on the metacognitive control of learning.

For example, Soderstrom and Bjork (2014) investigated how far restudy ver-

sus retrieval practice affect self-regulated study time. They showed that learn-

ers, after an intermediate test, deployed more study time to items that were

previously missed than those that were successfully recalled and increasingly

so the more difficult the items were. Learners, after restudy, however, did not

spent more time on the items than learners, after intermediate testing, did on

successfully recalled items (see also Son & Kornell, 2008) and the study-time

allocation did not reflect differences in item difficulty. Without a testing ex-

perience, learners overestimate the amount to which they have mastered the

16

learning of the to-be-remembered materials (for a review, see Bjork, Dun-

losky, & Kornell, 2013). In sum, testing facilitates metacognitive monitoring

(Kornell & Rhodes, 2013; Kubik, Soderstrom, Jemstedt, & Jönsson, 2014a,

2014b) and metacognitive control of learning (Karpicke, 2009).

Testing facilitates not only long-term retention of previously studied infor-

mation but also learning of subsequently presented new information (for a re-

view, see Pastötter & Bäuml, 2014). Szpunar, McDermott, and Roediger

(2008) demonstrated this so-called “forward effect” of testing in a multiple-

list learning experiment. Participants learned five consecutively presented lists

of words for a final cumulative recall test. Between studying Lists 1–4, they

solved either mathematical tasks, restudied the information, or attempted to

recall the most recently presented list. When recalling List 5, participants in

the tested condition recalled significantly more items and with significantly

fewer intrusions from previous lists than participants from the two nontested

conditions. Thus, testing shows not only a “backward effect” on previously

learned information but also a positive forward effect on the future learning

of new information.

However, as noted previously, selective retrieval of some events (e.g., a

birthday party) can be detrimental to the retrieval of other events. Similarly,

the retrieval of specific details of an event can attenuate the retrieval of other

details of the event. Such retrieval-induced forgetting (RIF) has been typically

studied in the retrieval-practice paradigm (for a seminal study, see Anderson

et al., 1994). Subjects study category–exemplar pairs (e.g., “fruit–apple,” “an-

imal–elephant,” “fruit–banana,” “animal–giraffe”) before they are (repeat-

edly) prompted to retrieve half the items from half of the categories (e.g.,

“fruit–ap__”). The critical finding is that nonpracticed items from the prac-

ticed categories (e.g., “giraffe”) are remembered worse on a subsequent

memory test than the control items from the nonpracticed categories (e.g., “ap-

ple,” “banana”). RIF is a reliable phenomenon (for narrative reviews, see

Raaijmakers & Jakab, 2013; Storm & Levy, 2012; for a meta-analytic review,

see Murayama, Miyatsu, Buchli, & Storm, 2014) and seems to be most pro-

nounced when nonpracticed (competitor) items are moderately associated to

the category and thus induce medium levels of interference during prior re-

trieval practice (Keresztes & Racsmány, 2013). It has been proposed that se-

lective retrieval practice either inhibits or blocks access to nonpracticed infor-

mation in memory at future retrieval occasions, depend on how retrieval-in-

duced forgetting is measured (Storm & Levy, 2012; Murayama et al., 2014).

Conversely, in some situations retrieval of some specific information can sup-

port and guide the retrieval of other information (Bäuml & Samenieh, 2010;

Collins & Loftus, 1975). For example, positive effects of selective retrieval

have been observed when the retention interval between study and retrieval is

prolonged or when the internal, spatial or social or context is changed (e.g.,

Bäuml & Schlichting, 2014). In these cases, the encoding context is less avail-

able and may need to be reactivated (Bäuml & Samenieh, 2012). Such rein-

statement of the context is enhanced through retrieval (Karpicke et al., 2014).

17

Thus, the memory dynamics after selective retrieval can be self-restricting or

self-propagating, in part depending on the presence or absence of contextual

change.

In conclusion, testing benefits learning directly via the completion of the

successful retrieval act and indirectly by enhancing subsequent re-encoding.

However, the retrieval of particular information from memory can also impair

the retrieval of other information.

Explanations of the Testing Effects

Despite the extensive research on the multitude of test-related effects, the pro-

gress of theoretical understanding lags behind (cf. Roediger & Butler, 2011),

and the underlying mechanisms remain unclear. Notably, no general theory of

the various testing phenomena has been formulated yet; rather, we only have

separate accounts of each type of testing effect. In the following discussion, I

will outline the main accounts of the positive effects of testing, as I primarily

focus on them in the present thesis.

Direct Testing Effect

Numerous accounts have been proposed to explain the direct effect of testing.

I will focus here on the item-specific and relational processing account, the

semantic-elaboration account, and the memory-strength account. These ac-

counts have received much empirical support and are discussed in the studies

conducted as part of this thesis. Two other theories, the amount-of-processing

and transfer-appropriate processing accounts, will be mentioned first, as they

have been influential but have rendered less empirical support in recent years.

Early Accounts

The amount-of-processing account (Dempster, 1996; Slamecka & Katsaiti,

1988; Thompson et al., 1978) states that long-term retention is not promoted

by testing per se, but by overlearning of the subset of items that are re-exposed

during successful retrieval. This early account has not received much support.

For example, tested material (i.e., ST) is typically better retained than non-

tested material that was not further processed (i.e., S–) or material that re-

ceived additional restudy (i.e., SS). Strictly speaking, the restudy condition

permits even more re-exposure to the material than the testing condition, as

all materials are restudied, whereas often not all materials are successfully

recalled in a test situation (Karpicke & Roediger, 2008). Thus, additional re-

exposure to material during testing can be neglected as a necessary factor ex-

plaining the direct testing effect.

The transfer-appropriate processing account (Blaxton, 1989; Morris,

Bransford, & Franks, 1977) states that the final test performance is a function

18

of the match between processes required at the final test and those initiated

during encoding. The greater the encoding–retrieval match, the better is the

memory performance (Kolers & Roediger, 1984; Morris et al., 1977). This

account can explain the testing effect in that interpolating tests during the

learning phase increases the similarity to the final test. However, the predic-

tion that identical test formats between intermediate and final tests should re-

sult in the strongest testing effects has not always been supported. In fact, the

testing effect increases as a function of retrieval difficulty during both initial

and final tests (cf. Halamish & Bjork, 2011). The testing effect is more pro-

nounced when more demanding retrieval measures are used, such as free recall

(Carpenter & Delosh, 2006; Glover, 1989) or tests involving brief answers

(Kang, McDermott, & Roediger, 2007; McDaniel, Anderson, Derbish, &

Morisette, 2007), instead of less demanding measures such as cued-recall or

recognition tests (Halamish & Bjork, 2011).

These two early accounts are descriptive and do not provide a satisfactory

explanation for several findings, such as the impact of retrieval effort on the

direct testing effect.

Item-Specific—Relational Processing Account

The item-specific and relational processing account has successfully ex-

plained the testing effect for word pairs (Karpicke & Zaromb, 2010; Mulligan

& Peterson, 2014; Peterson & Mulligan, 2013; Zaromb & Roediger, 2010)

and for visual–spatial information (Blunt & Karpicke, 2014; Karpicke &

Blunt, 2011). Recent research has shown that testing via cued recall leads to

higher retention compared with reading or generating information, both in fi-

nal recognition and in free-recall tests (when intermixing the presentation of

both study types). Both findings indicate that an increased amount of item-

specific processing is elicited through testing (Karpicke & Zaromb, 2010).

Furthermore, testing also enhances cue–target relational processing—a type

of processing that is especially required in cued-recall tests (Carpenter, 2011;

Kubik, Söderlund, Nilsson, & Jönsson, 2014; Peterson & Mulligan, 2013).

When free recall (and not cued-recall) is used in the intermediate tests and lists

of categorized items are given, testing also enhances the semantic processing

between items, as indicated by an increased number of recalled categories and

a correlation with free-recall performance (Congleton & Rajaram, 2011; Za-

romb & Roediger, 2010). However, testing seems to disrupt the retention of

order information (Karpicke & Zaromb, 2010; Mulligan & Peterson, 2014).

Thus, the way, in which testing is implemented, influences the nature of the

elicited retrieval processes.

The most prominent contribution of this account is the theoretical predic-

tion of a negative testing effect. Peterson and Mulligan (2013) assumed that

testing via cued recall enhances item-specific processing and the encoding of

cue–target relations at the expense of inter-item relational information (e.g.,

categorical or temporal relationships between items across trials). To investi-

gate this notion, the authors applied a typical testing-effect paradigm, which

19

included three phases. In Phase 1, 36 rhyming cue–target word pairs (with

targets stemming from six semantic categories) were studied and subsequently

either restudied or tested by cued recall. In Phase 2, the items were presented

in their category groups. After a 15-min distractor task, a final test was given

(either free recall, cued recall, or recognition; Mulligan & Peterson, 2014; Pe-

terson & Mulligan, 2013). As the testing was presumed to encode item-spe-

cific and cue–target relational information during Phase 2 at the expense of

inter-item information (i.e., the items’ categories), a positive testing effect was

predicted in recognition and cued-recall tests that drew on item-specific and

cue–target relational information, respectively. In contrast, a negative testing

effect was predicted for free recall of targets, as this memory test additionally

relies on categorical information that should have been less encoded for tested

items during Phase 2. These predictions were supported; testing produced

worse recall performance and less categorical clustering than restudy in the

free-recall test, whereas positive effects were found in cued-recall and recog-

nition tests.

In sum, testing promoted item-specific and cue–relational processing at the

expense of inter-item relational processing when retrieval was practiced with

a cued-recall test. However, the processes underlying testing are adaptive to

the specific task requirements (e.g., type of memory tests). Testing with free

recall can facilitate both item-specific and inter-item relational processing.

Semantic-Elaboration Account

According to the semantic-elaboration account, memory retrieval elicits se-

mantic elaboration in terms of adding extra information to the representation

of the learned items (the elaborative retrieval hypothesis; Carpenter, 2009;

Carpenter & DeLosh, 2006). When one retrieves the target word (e.g.,

“bread”) from a cue word (e.g., “basket”), other items are activated that are

semantically related to the cue (e.g., “eggs,” “flour”). These semantic media-

tors (Carpenter, 2011) help to link cue and target words and provide additional

retrieval routes to the target word. The more difficult the act of retrieval is, the

more elaborate is the semantic search of memory of the target word, and the

more semantic associates are activated to mediate the cue–target relationship.

This benefits later retention of the target word. However, restudy involves lit-

tle elaboration when only the entire cue–target pair is presented.

In support of this assumption, the testing effect was greater for weakly re-

lated compared with strongly related cue–target pairs (Carpenter, 2009), for

more difficult tests (e.g., free recall compared with recognition; Kang, McDer-

mott, & Roediger, 2007), and after longer RIs (Karpicke & Roediger, 2007;

Pyc & Rawson, 2007). Furthermore, testing cue–target pairs increased the

false alarm rate of target-associated distractor items (i.e., semantic mediators)

compared to restudying, and it increased later target recall when the semantic

mediator was used as the cue word (Carpenter, 2011). These findings suggest

that testing activates additional, semantically related information.

20

Memory-Strength Account

An early and still influential idea used to explain the testing effect is related

to the strength of memory traces or representations (Bjork, 1975, 1994). Ac-

cording to the memory-strength view, any form of studying strengthens the

underlying representations of the learned information. Furthermore, it is as-

sumed that memory retrieval leads to even greater strengthening than restudy,

as it requires more effort and thereby produces deeper retrieval processing

(retrieval-effort hypothesis, Bjork, 1975). To measure the retrieval effort, sev-

eral factors have been varied, such as the cue support given for retrieval prac-

tice during learning (Carpenter & DeLosh, 2006; Finley, Benjamin, Hays, &

Bjork, 2011) or the criterion to be achieved at the end of the learning phase

(Pyc & Rawson, 2009).

Testing is thought to improve long-term memory by reducing forgetting,

but more more recent implementations of this idea have proposed that testing

only appears to reduce forgetting relative to restudy and that the testing effect

may instead be explained through different memory-strength distributions re-

sulting from testing and restudy (Halamish & Bjork, 2011; Kornell et al.,

2011). This bifurcated-distribution model—a simplified version of the classi-

cal New Theory of Disuse (Bjork & Bjork, 1992)2—assumes that the to-be-

learned items are normally distributed in memory strength (as a first approxi-

mation; cf. Halamish & Bjork, 2011), which changes as a function of study

type. In the testing condition, correctly recalled items are presumed to gain

dramatically in memory strength, whereas nonrecalled items are presumed to

remain unchanged (Halamish & Bjork, 2011; Kornell et al., 2011) or even

decline in memory strength (given the evidence for retrieval-induced forget-

ting, see Anderson et al., 1994). The result is a bifurcated distribution of

memory strength for tested items. In contrast, in the restudy condition, all

items are re-exposed and receive a similar boost in memory strength, such that

the items remain normally distributed across items and participants. Even as-

suming equal rates of forgetting, these different item-strength distributions

would give the memory advantage to restudy conditions after shorter RIs (i.e.,

the items studied more extensively would have a memory strength above the

threshold) and to testing conditions after longer RIs; most successfully tested

items would still reside above the threshold despite a decrease in memory

strength over time.

Importantly, most of the central findings related to the testing effect are

consistent with this account, including the moderating influence of retrieval

difficulty of the intermediate and final test on the direct testing effect

2 The new theory of disuse further distinguishes between retrieval strength (i.e., the current

target access given the cue word) and storage strength (i.e., the degree of association strength

between the target word and other item representations). Retrieval strength determines the cur-

rent recall performance at any given moment (i.e., memory strength), while storage strength

acts as a latent variable that moderates the gain and loss functions of retrieval strength across

time and restudy events. However, it is beyond the scope of this review to further elaborate on

this dual-strength version of the distribution model.

21

(Halamish & Bjork, 2011), spacing effect of testing (Landauer & Bjork,

1978), and role of feedback or restudy (Kornell et al., 2011). This account has

led to new theoretical predictions (Storm, Friedman, Murayama, & Bjork,

2014; van den Broek et al., 2013). For example, as memory strength is higher

on average for retrieved items than for restudied items, retrieval latencies are

predicted to be shortened for tested items after a short RI. Such a finding of

test-reduced retrieval latencies in combination with the test–delay interaction

in retrieval performance has recently been provided (van den Broek et al.,

2013).

Indirect Testing Effect

Compared with the direct testing effect, the indirect effect of testing has re-

ceived much less empirical attention and the theoretical explanations of why

tests potentiate subsequent encoding are underdeveloped. As reviewed earlier,

they have been investigated based on several research designs: the inclusion

of additional restudy following the test trial (Arnold & McDermott, 2013a,

2013b; Nelson et al., 2013; Vestergren & Nyberg, 2014); immediate restudy,

given item by item during the test trial; providing corrective feedback; or pre-

testing the items (Grimaldi & Karpicke, 2012; Hays et al., 2013; Kornell,

2014; Kornell et al., 2009). As the studies included in this thesis concerned

repeated study–test practice in a multitrial paradigm, I will focus on the theo-

retical notions suggested to explain the indirect testing effect involving sepa-

rate, subsequent restudy (Grimaldi & Karpicke, 2012; Kornell, 2014 for ac-

counts related to “generation-potentiated learning” on immediate restudy).

Researchers have commonly invoked the idea of elaborative retrieval in-

volving the use and shift of semantic mediators. This notion was most explic-

itly formulated in the semantic-mediator account by Pyc and Rawson (2012).

This account broadly consists of two hypotheses. First, it is posited that learn-

ers produce higher recall rates under repeated test–restudy practice as testing

generates more effective mediators that link the cue and target words in paired

associates (Pyc & Rawson, 2010). Importantly, this increased mediator effec-

tiveness is assumed to arise partially from a mediator shift that is elicited by

interleaved testing during restudy. More specifically, by attempting to recall

the target word during the test trial, learners have the experience of retrieval

success and retrieval failure for each item. In cases of retrieval failure, learners

are prompted to replace the previously used mediator(s) with more effective

ones during restudy; in cases of retrieval success, they likely continue to gen-

erate the previous mediators. On the other hand, as restudying the material

(without testing) does not provide systematic retrieval experience, only a

slight mediator shift is prompted, even in cases where it would be useful.

Support for this account was given with a specific keyword-generation pro-

cedure (Pyc & Rawson, 2012). During initial study, participants learned Swa-

hili–English word pairs (e.g., “wingu–cloud”) and subsequently received ei-

ther repeated test–restudy or restudy-only practice. Critically, after each (re-

22

)studied item, a keyword mediator (“wing”) that is phonologically similar to

the Swahili cue word (“wingu”) and semantically connected to the English

target word (“cloud”) should be generated and reported. After two days, a final

cued-recall test was given, followed by a memory test for the keyword medi-

ators. The results supported the theoretical predictions. Beyond the increased

recall performance for the test–restudy compared with the restudy-only con-

dition, keyword mediators were more likely to be shifted in the test–restudy

condition and shifts occurred more often following retrieval failure compared

with retrieval success. In addition, after interleaved testing, more keyword

mediators were recalled.

Several points remain unclear, however. For example, participants do not

normally receive instruction to generate semantic mediators (e.g., keywords)

during encoding, and they might not spontaneously generate mediators at all

if not prompted to do so. It is possible, though, that nonrecalled or incorrectly

recalled items may at least receive additional attention and thus may be asso-

ciated with more effective encoding strategies during restudy (the strategy-

shift hypothesis, Bahrick & Hall, 2005). Furthermore, it is still unknown how

the learner is informed about the items’ retrieval status (recalled vs. nonre-

called) during restudy. This diagnostic information needs to be conveyed

somehow to the learner at the time of restudy, as it is separated from prior

testing through many items presented in between.

Two recent theoretical suggestions shed light on this issue. First, Nelson et

al. (2013) suggested that retrieval processes occur involuntarily during restudy

(Greene, 1989) and that these retrieval processes are increased through test-

potentiated learning. They reported as evidence that not only retrieval practice

per se (compared with restudy or no study at all) but specifically the amount

of new learning was associated with increased activations in the left lateral

and medial parietal cortex (i.e., the left posterior inferior parietal lobule

[pIPL]/dorsal angular gyrus [AG]). Participants who learned a higher propor-

tion of the previously nonrecalled items during restudy exhibited greater acti-

vation in this brain region, though this correlation was not present with regard

to recall performance for previously recalled, restudied, or nonstudied items.

As the pIPL/AG region features often successful recognition performance

(Nelson et al., 2010) or involuntary attention to an unexpectedly familiar stim-

ulus (Jaeger, Konkel, & Dobbins, 2013), these activations may reflect remind-

ings of the previous, unsuccessful recall attempts (Hintzman, 2004) or at least

of the tested cues (as the targets were not recalled).

Second, Vestergren and Nyberg (2014) suggested that tested items may be

differentiated from other items during restudy by means of an automatic tag-

ging process; they proposed that the cues of tested items are tagged during the

recall attempt with regard to their testing status. The cue word and its associ-

ated tag may then be retrieved during restudy, making the tested items more

salient. As evidence, they reported that the AI—a region prominently involved

in attention and specifically in salience tagging of items (Menon & Uddin,

2010)—showed more activation during the restudy of tested items that were

23

then successfully recalled in the post-restudy test compared with those items

that were not recalled. In turn, tested items may receive more and deeper re-

encoding, as the authors demonstrated in terms of increased activations in the

left hippocampus and the ventrolateral prefrontal cortex (left orbital part of

the inferior frontal gyrus [LOIFG]). Both these brain regions are involved in

the encoding processes of memory; the left hippocampus has been linked to

the binding of items within an event (Sullivan Giovanello, Schnyrer, & Ver-

faellie, 2004) and the LOIFG to the controlled access to concepts (Badre &

Wagner, 2007). However, the activations in both regions did not differ as a

function of the recall status of tested items. Thus, the indirect testing effect

may occur for not only unsuccessful but also successful retrieval attempts—

that is, for all tested items in general.

In sum, testing enhances the re-encoding of information during restudy.

However, the underlying mechanism for such test-potentiated learning re-

mains unspecified, partly because behavioral paradigms provide only indirect

evidence about the mechanisms employed during restudy by analyzing pre-

and post-restudy recall. Recent findings suggest that in addition to enhanced

re-encoding, study retrieval (in the form of remindings) and an attention-mod-

ulating tagging mechanism help to identify and boost the encoding of tested

items when restudy is given at a separate time after a delay.

24

How Does Motor Enactment Affect Memory?

Enactment Effect

Several research groups (Cohen, 1981; Engelkamp & Krumnacker, 1980;

Saltz & Donnenwerth-Nolan, 1981) independently developed the experi-

mental paradigm of subject-performed tasks (SPTs; for reviews, see

Engelkamp, 1998, 2001; Nilsson, 2000) with two different goals. Cohen

(1981) investigated memory for actions as a means for testing the generaliza-

bility of principles that have been reliably established in research on verbal

learning and memory with word materials. Engelkamp and Krumnacker

(1980) sought to explore ways to enhance memory by optimizing encoding

strategies.

In SPTs, the participants are requested to encode a list of action phrases

(mainly in the form of verb–noun phrases, e.g., “open the window”) and per-

form the specified actions. SPTs have traditionally been compared with verbal

tasks (VTs), in which the same items are verbally encoded under standard

learning conditions (visual or acoustical presentation) without the need to ad-

ditionally enact them. The by now well-replicated finding is that SPTs are

better remembered than VTs. This enactment effect improves memory perfor-

mance by approximately 20%–30% (Nyberg & Nilsson, 1995) and has been

reliably demonstrated across various recall tests, such as free recall (Peterson

& Mulligan, 2010; Schatz, Spranger, Kubik, & Knopf, 2011; see also Kubik

& Knopf, 2014), cued-recall (Kormi-Nouri, 1995; Steffens, Jelenec, & Meck-

lenbräuker, 2009), and recognition tests (Engelkamp, Zimmer, Mohr, & Sel-

len, 1994; Russ, Mack, Grama, Lanfermann, & Knopf, 2003; Steffens, Jele-

nec, Mecklenbräuker, & Thompson, 2006). However, in addition to verbal

encoding, other control conditions have been employed, such as motor im-

agery (Ecker & Engelkamp, 1995) and observing the experimenter performing

the actions (experimenter-performed tasks (EPTs), Cohen, 1981; Koriat, Ben-

Zur, & Druch, 1991; Schult, Stülpnagel, & Steffens, 2014). Typically, SPTs

are also better retrieved than these control tasks, but this depends on the ex-

perimental design and the chosen memory test (for a review, see Zaromb &

Roediger, 2010).

The enactment effect is also reliable across various encoding variables (in-

tentional and incidental learning: Zimmer & Engelkamp, 1984; blindfolded

participants: Engelkamp, Zimmer, & Biegelmann, 1991; Kormi-Nouri, 2000)

and types of memory tests, as reported earlier. Analyses from the population-

based Betula study, which included 1000 participants in the age range of 35–

25

85 years, demonstrated that approximately 88% of the participants revealed a

positive enactment effect (Nyberg, Persson, & Nilsson, 2002). Furthermore,

this encoding effect has been observed for many populations, for example, for

people with sensory disabilities (hearing impairment: von Essen & Nilsson,

2003; Zimmer & Engelkamp, 2003; visual impairment: Kormi-Nouri, 2000),

people with mental disabilities (Alzheimer’s disease: Karlsson et al., 1989;

amnestic mild cognitive impairment: Karantzoulis, Rich, & Mangels, 2006;

mental retardation: Cohen & Bean, 1983; Parkinson’s disease: Knopf, Mack,

Lenel, & Ferrante, 2005), and people across the life span (children: Cohen &

Stewart, 1982; Knopf, 1992; younger adults: Spranger, Schatz, & Knopf,

2008; older adults: Freeman & Ellis, 2003; Rönnlund, Nyberg, Bäckman, &

Nilsson, 2003).

Although this encoding effect seems to be robust in nature, some studies

have failed to replicate it. For example, people diagnosed with schizophrenia

(Daprati, Nico, Saimpont, Franck, & Sirigu, 2005) did not exhibit any enact-

ment effect nor did people diagnosed with frontal lobe syndrome, suggesting

that processes related to action planning may contribute to the enactment ef-

fect (Knopf et al., 2005). Furthermore, Engelkamp (1986) showed that for

paired-associate learning, enactment disrupts rather than enhances later

memory performance. More specifically, during the learning of verb–verb

pairs under verbal or enactive encoding instructions, enactment leads to worse

cued recall (i.e., recall of one the verbs prompted by the other) compared with

verbal encoding. However, when the participants were explicitly instructed to

integrate both verbs into an action, the negative enactment effect disappeared

(Engelkamp, Mohr, & Zimmer, 1991; Helstrup, 1991). Additionally, enact-

ment does not spontaneously facilitate the retention of temporal information.

That is, in serial recall tests, when the participants tried to recall the learned

items in the original order of encoding or reconstruct the temporal order when

the items were presented to them, they did not perform better after enactment

compared with verbal encoding (Olofsson, 1996). Finally, after enactment of

the action phrases, the participants could not effectively predict their future

recall performance with respect to which item would later be remembered and

which would not be remembered. Memory predictions for word material were

reliably higher (Cohen, 1983, 1988, 1989; Cohen & Bryant, 1991), suggesting

that enactment seems to hamper metacognitive monitoring.

Strikingly, several reliable phenomena established in verbal learning re-

search have failed to be replicated in SPTs. For example, deep (i.e., semantic)

relative to shallow (i.e., phonological) processing typically boosts memory

performance (for a seminal study, see Craik & Lockhart, 1972). This levels-

of-processing effect was nonexistent or reduced in SPTs (Cohen, 1981; Nils-

son & Craik, 1990; Zimmer & Engelkamp, 1999). Similarly, the mnemonic

effects of generating relative to reading or hearing information were not ob-

served for SPTs (i.e., generation effect; Nilsson & Cohen, 1988). Furthermore,

it was shown that enactment changes the typical U-shaped serial position

26

curve by shortening or eliminating the primacy effect and extending the re-

cency effect (Cohen, 1981; Schatz et al., 2010; Seiler & Engelkamp, 2003;

Zimmer et al., 2000).

In sum, although the enactment effect is a pervasive encoding phenomenon,

there are experimental circumstances and conditions in which this effect does

not emerge. Furthermore, a peculiarity of enactive learning and memory for

actions (i.e., SPTs) is that several robust memory phenomena from the verbal

domain are not replicated in an enactive encoding context or are at least di-

minished.

Explanations of the Enactment Effect

Several robust phenomena of verbal learning research are decreased or lacking

in SPTs. These findings have raised the possibility that other laws may be at

work in the memory for actions. However, memory research has not supported

this claim, as these findings are not universal but rather dependent on the spe-

cific experimental conditions (e.g., design and retrieval tests). Thus, it might

be claimed that for memory in general (Roediger, 2008) and action memory

in particular (Zaromb & Roediger, 2010), no general law-like statements can

be made. Instead, four main explanatory accounts have been proposed to ac-

count for the existence and variable size of the enactment effect (for more

comprehensive reviews, see Engelkamp, 1998; Nilsson, 2000; Zaromb &

Roediger, 2010; Zimmer et al., 2001).

Cohen (1981, 1983) invoked the notion of enactment as an optimal form of

encoding that does not require any study strategies—such as rehearsal or cre-

ating associations among to-be-learned items—to enhance later memory per-

formance. Given the “automatic” nature of the enactment effect, it should in-

crease in size when strategy use is minimal during study or retrieval. Later,

Cohen (1989) added the assumption that motoric execution is a critical aspect

in producing the enactment effect; however, he provided no specific mecha-

nistic explanation.

Bäckman and colleagues (Bäckman & Nilsson, 1984, 1985; Bäckman,

Nilsson, & Chalom, 1986) proposed that enactment relies on not only nonstra-

tegic but also strategic processes (e.g., rehearsal). Reading the action phrases

employs strategic processes for both VTs and SPTs; however, SPTs involve

additional physical components (e.g., movement, involvement of real objects)

that are encoded nonstrategically (Bäckman et al., 1991, 1993). Furthermore,

they assumed that the retrieval of verbal components is explicit, whereas the

retrieval of physical information is implicit (Nilsson & Bäckman, 1989). On

the basis of this dual-component notion, the enactment effect should increase

in size when physical aspects are added and, in contrast, should decrease when

the amount of strategy use and thereby the verbal aspects are experimentally

reduced (e.g., by dividing the attention through a distractor task).

27

Engelkamp and colleagues (Engelkamp & Zimmer, 1983, 1984, 1985) pro-

posed a third account. They claimed that the additional encoding of motor

information leads to the enactment effect. In later years, they developed a sys-

tem-oriented approach, according to which episodic memory can be divided

into independent, modality-specific systems. Expanding upon the dual-code

theory of Paivio (1971), they assumed separate systems for verbal and visual

input modality and for motoric output modality, with each of them comprising

specific codes and representational formats. According to this view, perform-

ing actions activates an additional motor system and enriches the representa-

tions, which in turn results in the enactment effect. Engelkamp and colleagues

(Engelkamp, 1990) added the notion of item-specific and relational processing

to action memory—a notion that has become popular in verbal learning re-

search (for a seminal paper, see Hunt & Einstein, 1981; Hunt, 2006). Enact-

ment was supposed to foster the individual features of single items (i.e., verb

and noun). Relational processing between the single items and the semantic

categories to which the noun components of the phrases belong were supposed

to be independent of the enactment effect (Engelkamp, Seiler, & Zimmer,

2005; Engelkamp & Zimmer, 1994). Later, they included the assumption that

enactment depends primarily on nonstrategic processes and, more specifi-

cally, that it may trigger an automatic “pop-out” retrieval mechanism (Zimmer

et al., 2000).

Finally, another account was proposed by Kormi-Nouri and colleagues

(Kormi-Nouri, 1995; Kormi-Nouri & Nilsson, 1998, 1999). In contrast to the

previous accounts, they assumed that enactive encoding is strategic and that

enactive and verbal encoding are two different variants of conceptual pro-

cessing, differing only in the degree to which the learner becomes involved

during encoding. The increased self-involvement following enactment brings

a more fine-grained registration of the situation and leads to the following

“integration” effects. First, action phrases become more strongly related to

each other, for example, by virtue of the shared semantic category (“between-

item integration”). Second, the verb and noun components within action

phrases become more related to each other (“within-item integration”). Third,

the participants become more integrated with the environment (“subject–en-

vironment integration,” Kormi-Nouri & Nilsson, 2001). As all three integra-

tive effects are critical for the enactment effect and occur simultaneously dur-

ing an encoding episode, they called it the “episodic integration account”

(Kormi-Nouri & Nilsson, 1998). Translated to the item-specific–relational ac-

count, these authors assumed that enactment fosters not only item-specific

processing but also category-relational and verb–noun relational processing.

Furthermore, they viewed episodic memory as a unitary memory system

(Tulving, 1972, 1983) that permits one to recollect past experience, irrespec-

tive of whether information is encoded verbally, visually, or motorically.

Thus, in contrast to the account by Engelkamp and colleagues, no separate

modality-specific systems are required to explain the enactment effect.

28

Theoretical Questions

In general, the accounts reviewed above present three theoretical dimensions

that can be viewed as three theoretical questions. Which among the following

does enactment rely on: item-specific versus relational processing, conceptual

versus motoric elaboration, or automatic versus strategic processing? Contem-

porary research attempts to answer these more specific research questions ra-

ther than the previously outlined accounts. Much attention has been focused

on the notion of item-specific versus item-relational processing, which is also

central to the studies comprising this thesis.

Item-Specific versus Relational Processing

Theoretical discourse has been extensively evaluated in terms of the assump-

tions regarding item-specific and relational processing, which is a central ac-

count in the verbal learning tradition (Einstein & Hunt, 1981; Hunt, 2006;

Hunt & McDaniel, 1993; Mulligan & Lozito, 2004). According to this ac-

count, enactment can potentially facilitate two processes: item-specific and

item-relational processing. Item-specific processing refers to the encoding of

the items’ individual features that makes them distinct from each other and

thereby better recallable at retrieval. Cue–target relational processing refers

to encoding of the association between the cue and target word and, in the case

of action phrases, between the verb and noun (i.e., verb–noun relational pro-

cessing). As the whole phrase is considered as the unit of analysis, this binding

mechanism is often referred to as (within-) item integration and regarded as a

type of item-specific processing (Kormi-Nouri, 1995; Kormi-Nouri & Nils-

son, 1998, 2001; Kubik, Söderlund et al., 2014; Steffens, Buchner, Wender,

& Decker, 2007; Steffens et al., 2009). Inter-item relational processing refers

to the encoding of information that is shared between items, such as temporal,

semantic, and/or idiosyncratic associations among them, and is supposed to

constrain the search for the to-be-remembered items (Hunt, 2006; Hunt &

McDaniel, 1993). For example, “apple,” “banana,” and “cherry” all share the

same category-relational information “fruit.”

The prevalent theoretical discourse generally agrees that enactment pro-

motes item-specific and cue–target relational processing of the action phrase

(Koriat, 1995; Seiler & Engelkamp, 2003; Steffens et al., 2006, 2009), which

makes action phrases more distinctive (Spranger et al., 2008; Zimmer, Hel-

strup, & Engelkamp, 2000). For example, evidence has been provided that the

enactment effect is pronounced in cued-recall (Steffens et al., 2006; Wippich

& Mecklenbräuker, 1995) and recognition tests (Perrig & Hofer, 1989; Stef-

fens et al., 2009) that mainly tap item-specific information. However, in free-

recall tests, the enactment effect is often diminished (Earles & Kersten, 2000)

and occasionally even nonexistent (Brooks & Gardiner, 1994; Knopf, 1995;

Steffens, 1999; cf. Steffens et al., 2009). These findings have been explained

by the fact that successful free recall relies on additional inter-item relational

29

information, which is not enhanced in SPTs, at least not in cases of symbolic

enactment, i.e., where no action-related objects are used (Engelkamp & Zim-

mer, 1996; Koriat, Pearlman-Avnion, & Ben-Zur, 1998; Steffens et al., 2009;

Zimmer, 1991).

For example, Steffens and colleagues (2006, 2009) confirmed these find-

ings by studying lists of action phrases as a function of the encoding type and

applying free- and cued-recall tests as well as verb- and noun-recognition

tests. For greater theoretical validity, they applied a multinomial modeling ap-

proach in which memory performance was decomposed into parameters re-

lated to item-specific processing for verbs and nouns, verb–noun relational

processing, and inter-item relational processing (which they termed “re-

trieval”; see Steffens et al., 2006, 2009, for more details). In addition to a sub-

stantial enactment effect, they demonstrated that enactment mainly increases

the parameters measuring item-specific and verb–noun relational processing.

These results confirm that enactment facilitates verb- and noun-specific pro-

cessing—as earlier shown in increased recognition and free recall perfor-

mance of verbs (Earles & Kersten, 2000; Engelkamp, Zimmer, & Kurbjuweit,

1995; Engelkamp, Zimmer, & Mohr, 1990; Freeman & Ellis, 2003) and nouns

(Earles & Kersten, 2000). Furthermore, cue–target relational processing is en-

hanced, which supports the previous findings of enhanced cued recall follow-

ing enactment. However, this seems to be the case only for verb–noun phrases

(Helstrup, 1993; Kormi-Nouri, 1995). Enactment is shown to hamper the cued

recall of verb–verb and noun–noun phrases (Engelkamp, 1986, 1995), or at

least enactment does not enhance the cued recall when no specific instruction

is given to integrate the phrases (Engelkamp, Mohr, & Zimmer, 1991; Hel-

strup, 1989, 1991).

Regarding inter-item relational processing, there exists substantial evi-

dence supporting the notion that enactment does not enhance this mechanism

relative to verbal encoding. For example, using lists of independent items,

Steffens et al. (2009) showed that the parameter measuring inter-item rela-

tional processing was not enhanced (Steffens et al., 2006) and was even ham-

pered in certain cases (Steffens et al., 2009) after enactive encoding. This is in

line with research demonstrating that idiosyncratic relations between items are

facilitated to a similar degree between encoding types (Koriat et al., 1998).

The temporal order among items (Olofsson, 1996) and the relation between

item and context (Koriat et al., 1991; Zimmer, 1994, 1996) is even less en-

coded during enactment. Furthermore, when providing items that are related

to a common taxonomic category, verbal and enactive encoding lead to similar

semantic clustering scores of items during free recall (Engelkamp et al., 2003;

Engelkamp & Zimmer, 2002), suggesting similar degrees of elicited category

relational processing. However, when including physical objects, SPTs were

more clustered than VTs in relation to the categories (Bäckman & Nilsson,

1984, 1985; Bäckman et al., 1986; Kormi-Nouri & Nilsson, 1999), even

though these clustering scores were often not positively correlated to memory

performance (Engelkamp & Zimmer, 1996; Zimmer & Engelkamp, 1989).

30

Thus, the involvement of real objects may moderate the influence of enact-

ment on category-relational processing (see also Nilsson, 2000). However,

Koriat and Pearlman-Avnion (2003) showed that encoding types facilitate dif-

ferent forms of organization; verbal encoding increased clustering along epi-

sodic–semantic concepts (e.g., gardening: “water a plant,” “snip a rose”),

whereas enactive encoding clustered action phrases with regard to the similar-

ity of the bodily movements (“twist a toothpaste cap,” “screw a wire in

place”). In sum, enactment seems to enhance item-specific information in

terms of the individual features of the verb and noun as well as their relation

within action phrases. Enactment, relative to verbal encoding of action

phrases, may also enhance organizational processing, probably along a simi-

larity dimension of body movements (Koriat & Pearlman-Avnion, 2003).

However, further research is needed to substantiate this hypothesis.

Conceptual versus Motoric Elaboration

It is widely agreed that enactive relative to verbal encoding provides an elab-

oration of the memory trace in one way or the other. However, it is debated

whether motor information is necessarily included in these elaborated memory

representations and how critical it is (cf. Engelkamp, 2001; Kormi-Nouri, &

Nilsson, 2001; Zimmer, 2001). The accounts from Cohen, Engelkamp/Zim-

mer, and Bäckman/Nyberg/Nilsson agree in more recent formulations on the

notion that the motor component is critical in the enactment effect. In addition,

Engelkamp and Zimmer (see Engelkamp, 2001) added the assumption that

episodic memory needs to be differentiated in independent information-pro-

cessing systems that are related to visual, verbal, and motor modalities (Zim-

mer et al., 2001). In contrast, other researchers explained the enactment effect

within one unitary system of episodic memory and assumed that the underly-

ing representations of enacted action phrases are elaborated using the same set

of conceptual processes that are also involved in other encoding manipulations

(e.g., differentiation vs. integration, Helstrup, 1987; episodic integration,

Kormi-Nouri & Nilsson, 2001; see also Knopf, 1992).

Research has not provided conclusive evidence to solve this issue. One line

of argument refers to the idea that if the motor component is critical, self-

performed actions (SPTs) should be better remembered than observed actions

(EPTs). Several studies confirmed this prediction (Engelkamp & Zimmer,

1997); however, others did not, and they showed equivalent memory perfor-

mance for both encoding tasks (Cohen, 1981; Steffens et al., 2007; Schult,

Stülpnagel, & Steffens, 2014). List length and experimental design seem to

moderate this pattern of results (Engelkamp & Zimmer, 1997): when EPTs

and SPTs were provided across subjects and in short lists, no enactment effect

emerged. However, superior SPT recall was observed when the list length was

increased (from 24 to 48 items) and both tasks were randomly mixed within

the lists during encoding. Thus, the results obtained were inconclusive. A sec-

31

ond line of evidence refers to brain-imaging studies that showed that the en-

actment effect is related to the motor areas in the brain. For example, when

measuring the differences in the regional blood flow via positron emission

tomography, brain regions—including the premotor cortex, motor cortex, and

sensosomatory cortex—showed increased activity both during encoding and

cued recall of action phrases (Nilsson et al., 2000; Nyberg et al., 2001). These

results suggest that encoded motor information is reactivated during retrieval.

However, these regions were similarly involved when no physical movement

was requested in the motor-imagery condition and likely also in purely “ver-

bal” processing of action phrases, though to a lesser degree. Thus, there seems

to be no qualitative difference in the underlying mechanism of reading and

acting out a phrase; rather, a quantitative difference is observed.

Automatic versus Strategic Processing

The notion that enactive encoding is nonstrategic has also been discussed. As

reviewed earlier, several robust memory phenomena that are related to the

employment of strategic processing have not been replicated in SPTs, or at

least these effects were substantially reduced, such as in the levels-of-pro-

cessing effect (Cohen, 1981; Cohen & Bryant, 1991; Nilsson & Craik, 1990),

generation effect (Nilsson & Cohen, 1988; see, however, Österreich &

Köddig, 1995), and primacy effect (Bäckman & Nilsson, 1984; Cohen, 1981;

Seiler & Engelkamp, 2003; Zimmer et al., 2000). All these effects are pre-

sumed to reflect the usage of strategies in one way or the other. The levels-of-

processing effect refers to the finding that words profit mnemonically from

deeper (i.e., semantic) relative to superficial (i.e., phonological) study strate-

gies. The primacy effect is assumed to emerge as a result of increased re-

hearsal of the first items in working memory. With increasing serial position,

the items in the study list are presumed to receive a decreasing amount of

rehearsal. Another line of evidence in favor of a nonstrategic account of SPT

enhancement on memory was that memory performance after enactment did

not vary with age (in children: Cohen & Stewart, 1982; in older adults: Bäck-

man & Nilsson, 1984, 1985) or intelligence (group with mental retardation vs.

control group, Cohen & Bean, 1983). Given that age and intelligence influence

verbal memory performance and the ability to employ study strategies, these

early findings were considered as evidence for enactment as an optimal, non-

strategic form of encoding that does not require any study strategies.

However, several findings dispute the nonstrategic, optimal nature of en-

active encoding. First, enactive encoding can be improved by several other

study strategies (e.g., repetition: Schatz et al., 2010, 2011; semantic clustering:

Bäckman et al., 1986). Additionally, dividing the attention during encoding

through an interference task can deteriorate the recall performance of SPTs,

suggesting that a certain degree of strategic processing is involved during en-

actment. Second, more recent studies showed developmental memory differ-

ences for SPTs (Knopf, 1991; Ratner & Hill, 1991), and a longitudinal study

32

on memory and aging showed similar trajectories of age-related decline in

VTs and SPTs (Rönnlund et al., 2003), suggesting that enactment does not

make people less resistant to strategy-related memory differences. Instead of

defining enactive encoding as intrinsically strategic or nonstrategic encoding,

Nilsson (2000) argued that the self-initiated use of strategies may rather de-

pend on task demands such as task difficulty or cue support during retrieval

(see also Knopf, 1992). In this regard, SPTs may require lesser strategy use in

many experimental situations than VTs or words, but the difference may be

quantitative rather than qualitative.

Methodological Considerations

Different research traditions have yielded different methodological ap-

proaches in action memory research. These differences have likely contributed

to the empirical and theoretical inconsistencies.

The first discrepancy pertains to the provision of physical objects that are

denoted by the noun in action phrases (e.g., a glass: “lift the glass”). Some

research groups typically provide the physical objects for SPTs, but not for

VTs (Rönnlund, Nyberg, Bäckman, & Nilsson, 2003; Nilsson, Adolfsson,

Bäckman, de Frias, Molander, & Nyberg, 2004). One reason to do so is to

instantiate enactment under more ecologically valid and realistic conditions.

Another reason is theoretical in nature; some researchers view the enactment

effect as related to the multimodal experience of performing an action with a

physical object (weight, texture, color, smell, etc.; Bäckman, Nilsson, & Cha-

lom, 1986; Kormi-Nouri & Nilsson, 1999). However, others (Engelkamp &

Zimmer, 1996; Schatz et al., 2010; Steffens et al., 2009) view the pure motor

execution of an action as critical. Typically, they let the participants symboli-

cally enact the phrases’ content in SPTs in order not to confound the facilita-

tive effects of object presence and motoric execution (SPTs-plus-objects vs.

VTs; see Steffens et al., 2007, 2009). However, as it turns out, the additional

provision of objects in SPTs is not crucial for the enactment effect (Engelkamp

& Zimmer, 1997; Kormi-Nouri, 2000; Zimmer & Engelkamp, 2003), though

it can moderate its magnitude under specific conditions (Steffens et al., 2007)

and influence the extent of semantic clustering in free-recall performance (cf.

Engelkamp et al., 2005).

Another less-discussed research practice refers to the “proper control con-

dition” for SPTs. VTs usually imply only silent reading of the action phrases,

whereas SPTs require reading and enacting the phrases. This permits research-

ers to evaluate the mnemonic value of enactment in addition to simply reading

(Engelkamp & Jahn, 2003; Schatz et al., 2011; Steffens, Buchner, & Wender,

2003; Steffens et al., 2009). However, in other studies, participants attentively

read and say the action phrases aloud (Spranger et al., 2008). Such vocally-

produced action phrases provide a stricter control condition for SPTs, as vocal

33

production is presumed to enhance distinctiveness and, consequently, the re-

tention of information (production effect; MacLeod et al., 2010). The relative

advantage of motoric versus vocal production of action phrases can then be

evaluated. Furthermore, some research used EPTs, and not VTs, as control

conditions. As reviewed earlier, SPTs outperform EPTs under experimental

conditions that facilitate item-specific processing (e.g., using long lists or giv-

ing recognition tests; Engelkamp, Jahn, & Seiler, 2003).

The last methodological discrepancy refers to the action-phrase material

used. Generally, rather simple, discrete action phrases were used (e.g.,

“sharpen the pencil”), and these were selected with regard to specific criteria,

such as excluding action phrases with body parts as nouns (e.g., “fold your

arms”) as they would be available cues during retrieval (see Schatz et al.,

2010; Spranger et al., 2008). To this end, the action phrase material was also

rated in order to standardize and control the various dimensions in which the

action phrases may differ (e.g., regarding familiarity and emotionality, see

Molander & Arar, 1998). On the other hand, others (Cohen, 1981) used action

phrases that differed largely and even included mental activities, such as “add

2 + 3,” whereas others applied complex, goal-oriented activities with the aim

of approaching everyday actions (Foley & Ratner, 2001; Schult et al., 2014).

Given these research traditions that vary across research groups, the enact-

ment effect has been demonstrated even under methodologically stricter con-

ditions, that is, if no action-related objects were given for SPTs (and VTs), if

the participants were asked in VTs to read and say the action phrases aloud

(Spranger et al., 2008), or even when the participants watched the experi-

menter performing the actions (Engelkamp & Zimmer, 1983, 1997; for more

complex, goal-directed action phrase materials, see Schult et al., 2014; Stef-

fens, 2007). The empirical studies contained in this thesis were conducted un-

der more methodologically “conservative” conditions, that is, use of simple

action phrases (without body parts as noun objects), VTs were to be read

aloud, and action-related objects were not provided for SPTs. EPTs were not

applied as an additional reference condition to SPTs.

34

Background, Research Objectives, and

Methods of Studies

Background

As noted in the preceding sections, retrieving information from memory not

only assesses but also produces learning. The act of retrieval alters the future

recallability of the retrieved information and enhances the subsequent re-en-

coding, specifically of nonrecalled information. These direct and indirect test-

ing effects have been demonstrated for various learning materials, though they

have not yet been investigated with action-relevant information. This is sur-

prising as everyday memory is typically concerned with past and future ac-

tions and may have developed, largely, to keep the same in mind. Thus, a

general aim of this thesis is to investigate the effects of testing with action

(i.e., verb–noun) phrases as the material to be learned.

The testing effect is often demonstrated by comparing test conditions to

nonstudying or additional, though ineffective, restudy conditions (cf. Kornell

et al., 2012; see recent exceptions in Karpicke & Blunt, 2011; Karpicke &

Smith, 2012). To evaluate the relative effectiveness of testing, active study

techniques should be considered as the comparison conditions. To this end, I

employed motor enactment as an active study technique. First, using action

phrases as the learning material, motor enactment is the major and most effec-

tive encoding form, as it produces substantive memory benefits relative to ver-

bal encoding (the enactment effect; for a review, see Roediger & Zaromb,

2010). Second, enacted phrases, in particular, mimic important aspects of real-

life actions and could explain how testing effects translate to more ecologi-

cally valid objects of everyday memory. Finally, enactment can be viewed as

a form of motoric production or generation of actions based on the verbal

descriptions of verb–noun phrases. From this perspective, motor enactment

instantiates a highly effective case of the more general, well-established en-

coding phenomena of the generation effect (Bertsch et al., 2007) and the pro-

duction effect (MacLeod et al., 2010). Therefore, results with enacted phrases

may be of more general importance. Thus, an additional general aim of this

thesis is to compare the relative and combined effects of testing (vs. study-

only) and motor enactment (vs. verbal encoding) on the learning of and

memory for action phrases.

Prior studies on action memory primarily investigated the mnemonic effect

of enactment in a single-trial learning paradigm, containing one study trial and

35

one test trial (for a review, see Nilsson, 2000). Only a few studies examined

this encoding effect over the course of several study–test cycles (multitrial

learning) and employed free-recall tests (Koriat et al., 2002; Koriat & Pearl-

man-Avnion, 2003; Kubik, Obermeyer et al., 2014a, 2014b; Nilsson et al.,

1989). These studies revealed that the robust memory advantage of enactment

decreases (Koriat & Pearlman-Avnion, 2003) or even vanishes in certain cases

(Kubik, Obermeyer et al., 2014a, 2014b). To this end, the present thesis ex-

amines whether the enactment effect persists over a multitrial learning phase

when it is assessed with a final cued recall. This was hypothesized to be the

case as cued recall is more sensitive to the enhanced cue–target relational pro-

cessing through enactment. Typically, tests in these multitrial learning para-

digms were simply given to measure the degree of learning across learning

trials (Koriat & Pearlman-Avnion, 2003; Kubik, Soderstrom et al., 2014b) or

the rate of forgetting (Nilsson et al., 1989), though their impact on memory

has not been controlled for. It should be noted that only one study (Nilsson et

al., 1989) investigated the rate of forgetting for longer retention intervals (RIs)

as a function of encoding type. During the learning phase, participants learned

several lists of action phrases, either verbally or enactively, with immediate

tests following each list. After several RIs (0, 1 days, or 1 week; Exp. 1), they

were asked to retrieve the items from all lists on a final free-recall test (i.e.,

multiple-list learning paradigm: Nilsson et al., 1989; Nyberg, Nilsson, &

Bäckman, 1992). Importantly, it was shown that the forgetting rate is similar

for verbal and enactive encoding. However, this finding may be affected by

the intermediate tests in that they have mitigated forgetting for the verbal more

than the enactive encoding condition. To evaluate this possibility, the included

studies considered the effects of interleaved testing in a multitrial learning

paradigm (i.e., STSTST) by adding a study-only control condition (SSSSSS)

in which the action phrases were exclusively restudied during the learning

phase. An additional testing was implemented after 1 week in order to assess

the rate of forgetting over time as a function of both study type (study–test vs.

study-only) and encoding type (verbal vs. enactive encoding).

The item-specific–relational processing framework provides an account for

several encoding phenomena in memory (e.g., production effect, generation

effect, enactment effect) and also the direct effects of testing (Mulligan & Pe-

terson, 2014; Peterson & Mulligan, 2013). From this theoretical standpoint, I

attempt to explain the individual and combined effects of testing and enact-

ment on the memory for action phrases. In the included studies, cued-recall

tests were employed, which primarily measure the strength with which the cue

item can elicit the target item. As the two study techniques are assumed to

commonly rely on cue–target relational processing (Mulligan & Peterson,

2014; Steffens et al., 2009), both testing (relative to study-only) and enactment

(relative to verbal encoding) should reduce the rate of forgetting with action

phrase material, and they should combine less than additively. However, if

both effects turn out to be additive when combined, they may rely on different

mechanisms. For example, it has been proposed that testing does not rely on

36

cue–target or other elaborative processes, as typically assumed for encoding

phenomena such as the enactment effect. Instead, direct testing effects are pre-

sumed to rely on retrieval-specific mechanisms that restrict the search set of

potential target candidates to the cue word (Karpicke & Smith, 2012; Karpicke

& Zaromb, 2010), for instance, by reinstating the previous items’ context

(Karpicke et al., 2014).

In everyday life, we typically perceive objects that remind us about the per-

formed and to-be-performed actions. It is still unclear whether the recall type

(noun-cued recall of verbs vs. verb-cued recall of nouns) moderates the effects

of testing on memory. Prior research on the learning of verb–noun pairs

(Earles & Kersten, 2000; Kormi-Nouri, 1995; Steffens et al., 2009) and paired

noun associates (for a review, see Ekstrand, 1966; Kahana, 2002) shows ap-

proximate symmetry with respect to the recall type, though no study has yet

investigated whether the effects of repeated study–test practice are also sym-

metrical across recall types with respect to action phrase material. In Studies

II and III, memory was tested through either verb-cued recall of nouns or

noun-cued recall of verbs in order to examine whether the type of recall mod-

erates the testing effect on the rate of forgetting. If testing with the two recall

types strengthens the verb–noun association to a similar degree, the rate of

forgetting should be similar for noun- and verb-cued recall.

So far, no study has addressed the indirect testing effects with action phrase

material. In Studies I–III, testing was instantiated through repeated study–test

practice. For this reason, an indirect testing effect can occur because testing

enhances the re-encoding of unsuccessfully recalled action phrases during

subsequent restudy. To evaluate this possibility, I calculated the number of

newly retrieved items from the pre- to the post-restudy tests (Arnold &

McDermott, 2013b) and examined whether this index of new learning differed

between recall types. Any difference in the amount of new learning would

reveal that the indirect testing effect occurs and differs in size for noun- versus

verb-cued recall of action phrases. In contrast to the expectations for the direct

testing effect, I hypothesized that the recall type may moderate the indirect

effects of testing. Noun-cued recall of verbs may produce more new learning

during subsequent restudy. Nouns—being semantically more stable and con-

crete than verbs (Earles & Kersten, 2000; Kersten & Earles, 2004)—should

be better recognized as prior retrieval cues and thereby may provide more re-

liable information regarding the recall status during restudy as compared with

verbs. This, in turn, should enhance the chances for previously nonrecalled

items to receive effective re-encoding following noun-cued recall as compared

with verb-cued recall. Although it is difficult to distinguish between both types

of testing effects in multitrial learning paradigms, it is important to consider

them to the extent possible.

37

Research Objectives

This thesis deals with the individual and combined effects of interleaved test-

ing (i.e., repeated study–test practice) and motor enactment on the memory

for action phrases. The studies included in this thesis are the first to aim at

such an integrative approach of these retrieval and encoding effects in action

memory. The main research objectives of the three empirical studies contained

in the thesis were to investigate

1. the direct testing effect with action phrase material. I examined the

relative effects of interleaved testing and study-only conditions on the

rate of forgetting over an interval of 1 week for both verbal encoding

(Studies I and II) and enactive encoding (Studies I and III).

2. the indirect testing effect with action phrase material. I examined the

test-potentiating effect on the subsequent re-encoding of previously

nonrecalled items for both verbal encoding (Study II) and enactive

encoding (Study III).

3. verb–noun asymmetry of testing effects. Are the direct and indirect

testing effects symmetrical with regard to recall type (noun-cued re-

call of verbs vs. verb-cued recall of nouns)? I investigated with regard

to this question for both verbal encoding (Study II) and enactive en-

coding (Study III).

4. the enactment effect. I examined the relative effects of enactive and

verbal encoding on short- and long-term retention as well as on the

forgetting rate (Study I; Studies II vs. III).

5. the combined benefit of the direct testing effect and the enactment ef-

fect on the rate of forgetting. Do they interact to produce nonadditive

effects, or are they additive? (Study I; Studies II vs. III).

38

Methods of Studies

Participants In Studies I–III, the participants included undergraduate students from Stock-

holm University, Uppsala University, and Södertörn University. Participation

was compensated with course credits or movie vouchers. The assignment of

participants to the experimental groups (study type and recall type) was ran-

dom. However, in Study I, the study-only groups were recollected because of

a programming error. In general, similar participant characteristics were re-

tained across groups, resulting in an equivalent gender ratio, mean age, and

working memory capacity for Studies I–III. Thus, potential selection bias ef-

fects seemed to be marginal between groups in each study, if at all existent.

However, in Study 2, however, there was a consistent difference observed in

the age between groups. When the two oldest participants were excluded in

preliminary analyses, the age difference was eliminated, but the result pattern

remained the same. Thus, age did not influence the results.

Materials Action phrases (e.g., “squeeze the lemon”) were used as stimuli and were

drawn from normative item pools (Study I: 36 items from Molander & Arar,

1998; Studies II and III: 40 items from Kormi-Nouri, 1995). To control for

item characteristics, action phrases were selected that were two to four words

long, comprised a verb and a noun, and did not include nouns that described

body parts (e.g., “lift the arm”) as these nouns would provide extra body-re-

lated cues during retrieval. Additionally, in Study I, action phrases were not

selected if they were bizarre (i.e., stemming from the lower tertile of the fa-

miliarity-rating distribution, such as “share a kiwi fruit”) or highly emotional

(i.e., stemming from the upper tertile of the emotionality-rating distribution).

Procedure A multitrial cued-recall learning paradigm was employed as the experimental

procedure, comprising a series of study and/or test trials3. During the study

trials, the participants were instructed to intentionally learn the action (i.e.,

verb–noun) phrases (e.g., “lift the glass”) displayed on the computer screen,

either by reading the action phrases aloud (i.e., VTs) or by enacting them sym-

bolically (i.e., SPTs). SPTs did not contain any physical objects corresponding

to the noun, as memory performance had to be investigated purely as a func-

tion of enactment (and not the additional or interactive involvement of ob-

jects). SPTs (i.e., motorically produced actions) were compared against a strict

control condition including another active study strategy of vocally producing

the action phrases (MacLeod et al., 2010). The participants were instructed to

3 In the term “multitrial learning paradigm,” trial refers to the whole study or test phase in

which a list of items or cues are presented. An event refers to the single presentation of each

item or cue.

39

attentively read the action phrases and say them aloud. During test trials, the

verb or the noun was given as a retrieval cue for the participant to recall the

other item of the action phrase. In all three studies, final recall tests were given

after a short and long RI.

Scoring and Analyses Participants’ responses were scored as correct if the original noun or verb was

entered on the keyboard. The data were analyzed with conventional analyses

of variance (ANOVA) and t-tests, as these are suitable statistical techniques

to investigate the statistical relationships between one or several independent

variables (dichotomic) and one continuous dependent variable (Tabachnik &

Fidell, 2005). An alpha level of .05 was used. Adjusted effect sizes are re-

ported for ANOVAs and t-tests. For ANOVAs, generalized omega squared

[ω̂G2 ] (for a statistical discussion, see Olejnik & Algina, 2003) are used as ef-

fect sizes, as the same is less biased for small samples (Carol & Nordholm,

1975) and estimates the effect sizes for the population. The generalized form

of omega squared is used, as it permits a comparison of the effect sizes across

studies and study designs (within- vs. between-subjects), though it can be sub-

stantially smaller. Partial forms of eta (or omega) squared, which are more

often used, are sensitive to design differences, as they partially reflect the error

variance that is reduced in within-subject designs. Adjusted forms of Cohen’s

d are used for t-tests (for independent groups, Cohen’s d unbiased [dunb]; for

dependent groups, Cohen’s dav; Cumming, 2014). Furthermore, 95% confi-

dence intervals for dunb/av, based on the noncentral t-distribution, are reported.

In cases when the assumption of sphericity was violated, the numbers using a

Huynh–Feldt correction are reported.

40

Overview of Studies

Study I

Kubik, V., Söderlund, H., Nilsson, L.-G., & Jönsson, F. U. (2014). Individual

and combined effects of enactment and testing on memory for action phrases.

Experimental Psychology. Advance online publication. DOI: 10.1027/1618–

3169/a000254

Objective

The objective of Study I was to investigate the individual and combined ef-

fects of interleaved testing and enactment on the rate of forgetting and long-

term retention of action phrases over a period of 1 week. I hypothesized that

both the study techniques effectively engage in verb–noun relational pro-

cessing that can only marginally, if at all, increase further when combining

them. Based on this notion, I predicted that both the study techniques reduce

the rate of forgetting, though their combined effects should be less than addi-

tive.

Background

As compared to restudying, interleaved testing reduces the rate of forgetting

over longer time periods such that long-term retention is enhanced for tested

information. This testing effect has been most frequently investigated in cued

recall (Carpenter, 2009, 2011) and is due to the successful act of memory re-

trieval, which reduces the rate of forgetting. Several authors have argued that

testing may specifically promote cue–target relational processing (Mulligan

& Peterson, 2014; Peterson & Mulligan, 2013) and item-specific processing

(Karpicke & Zaromb, 2010).

The enactment effect is a robust encoding effect that is specifically pro-

nounced in cued recall and recognition, due to promoting cue–target relational

and item-specific processing. However, little is known about how enactment

influences the retention of action phrases over longer time periods. There is

scarce evidence that enactment facilitates retention across RIs that are shorter

than one day (Knopf, 1991; Nyberg, Nilsson, & Bäckman, 1992), though for-

getting did not appear to be reduced over a 1-week interval, as Nilsson et al.

(1989) demonstrated.

41

In Study I, the testing effect was investigated with action-phrase material.

Its relative and combined effects with motor enactment on subsequent

memory performance were evaluated. More specifically, verb-cued recall was

given during intermediate and final tests, which primarily taps verb–noun re-

lational processing in the case of action phrases. As the mnemonic effects of

testing and enactment were commonly explained by this binding mechanism,

both the study techniques were predicted to exhibit similar effects on forget-

ting and to have nonadditive effects when they are combined.4 The additive

effects of testing and enactment suggest that they partly rely on different

mechanisms. In contrast to enactment, testing may reduce the search set dur-

ing cued recall instead of directly strengthening the specific verb–noun asso-

ciation.

Method

A total of 112 undergraduate students (i.e., four experimental groups of n =

28) engaged in a learning phase and two retrieval phases (for a specific de-

scription, see Figure 1).

Figure 1. Experimental procedure.

(From “Individual and combined effects of enactment and testing on memory for action phrases,” Kubik,

V., Söderlund, H., Nilsson, L. G., & Jönsson, F. U. (2014). Experimental Psychology. Advance online

publication. DOI: 10.1027/1618–3169/a000254. Reprinted and modified with permission from Experi-

mental Psychology. © 2014 Hogrefe Publishing, www.hogrefe.com)

The learning phase comprised four trials, each separated by a 30-s arithme-

tic filler task. In the study-only groups, the participants learned 36 action

phrases repeatedly during four study trials, either verbally (VT) or enactively

4 In action-memory research, this mechanism is regarded as an item-specific process, as the

entire action phrase is regarded as the “item unit” and becomes more distinctive. Thus, in

Study I, I used the term “item-specific processing.” In the thesis, however, I will use the more

precise term “verb–noun relational processing.”

42

(SPT). In the study–test groups, the participants alternately studied the learn-

ing material and cued-recalled it in intermediate tests. In the retrieval phases,

a final verb-cued recall test was given after short (18-min) and long (1-week)

RIs. A 2 (study type: study-only vs. study–test) × 2 (encoding type: SPT vs.

VT) × 2 (RI: short vs. long) mixed factorial design was used, with the first two

factors manipulated between subjects and the last factor manipulated within

subjects.

Results

Figure 2. Final cued-recall performance as a function of study type (study-only/study–

test) and retention interval (short/long), shown separately for verbal encoding (left

panel) and enactive encoding (right panel). Error bars represent 95% confidence in-

tervals (CIs) for the mean.

(From “Individual and combined effects of enactment and testing on memory for action phrases,” Kubik, V., Söderlund, H., Nilsson, L.-G., & Jönsson, F. U. (2014). Experimental Psychology. Advance online

publication. DOI: 10.1027/1618–3169/a000254. Reprinted and modified by permission from Experimental

Psychology. © 2014 Hogrefe Publishing, www.hogrefe.com)

As can be seen in Figure 2, interleaved testing relative to restudy practice re-

duced the rate of forgetting for action phrases. Consequently, a reliable

memory advantage emerged in favor of study–test items after the long RI,

whereas memory performance after the short RI was equal for both the study

types. However, this testing effect was only demonstrated for verbal and not

for enactive encoding. Furthermore, a robust enactment effect was demon-

strated after both the short and long RIs. The size of the encoding effect in-

creased from short- to long-term retention only in the study-only condition

due to the decreased rate of forgetting for enactive encoding. Thus, both test-

ing and enactment reduced the rate of forgetting, though this effect was less

than additive when the two were combined (study-onlyverbal > study-onlyenactive

= study–testverbal = study–testenactive) as demonstrated by a reliable interaction

effect between the study type and encoding type. As for long-term retention,

43

the combination of testing and enactment did not exceed enactment alone;

however, it exceeded the long-term retention of testing alone.

Furthermore, memory performance was equivalent for both study types af-

ter the short RI, despite the fact that the action phrases in the study–test con-

ditions were less often restudied than in the study-only conditions. This find-

ing may stem in part from the indirect testing effect, that is, the facilitating

effect of testing on the subsequent restudy trials, after both verbal and enactive

encoding.

Conclusions

This study provides evidence that the testing effect generalizes to action-

phrase material, similarly as for various other learning materials (English–

Swahili word pairs, Pyc & Rawson, 2012; text materials, Karpicke & Blunt,

2011). Importantly, the testing effect exclusively occurred for verbal encoding

but not for enactive encoding. One explanation for this resistance of enacted

materials to the testing effect is that testing—similar to motor enactment—

effectively establishes a close connection between the cue and target words

(Peterson & Mulligan, 2013), and further verb–noun relational processing be-

comes less efficient. This is in accordance with previous findings that several

otherwise robust memory phenomena (e.g., generation effect) have failed to

be replicated with enacted materials (Nilsson & R. L. Cohen, 1988).

In addition to the general enactment-related memory benefit, enactment re-

duced the rate of forgetting; however, this was observed exclusively for the

study-only condition. This finding complements previous research. Nilsson

and colleagues (1989) demonstrated equal rates of forgetting for verbal and

enactive encoding; however, they employed a multiple-list learning paradigm

with intermediate tests given immediately after each encoded list of action

phrases. These tests may have reduced the rate of forgetting to a higher degree

after verbal rather than enactive encoding and equalized potential differences

in the rates of forgetting.

However, the effects of enactment exceed those of testing after both the

short and long RIs. Combining both study techniques led to superior cued-

recall performance compared with testing, but not when compared with only

enactment. Thus, enactment can contribute to long-term learning beyond the

effects of testing.

Future studies should demonstrate the reliability of the presented findings

across the design status of study type (within- vs. between-subjects) and recall

type (verb- vs. noun-cued). Importantly, the indirect testing effect needs to be

explicitly considered, which also contributes to the final recall performance in

a repeated study–test versus study-only cued-recall paradigm.

44

Study II

Kubik, V., Nilsson, L.-G., Olofsson, J. K., & Jönsson, F. U. (2014b). Testing

effects on subsequent restudy and forgetting of action phrases. Manuscript

submitted for publication.

Objective

The objective of Study II was to examine both the direct and indirect effects

of testing on cued recall for verbally encoded action phrases and, importantly,

whether recall type (verb- vs. noun-cued) moderates these testing effects.

Background

Testing during learning reduces the rate of forgetting as compared with an

equal amount of restudy; I demonstrated this direct testing effect in Study I

with verb-cued recall of action phrases that were verbally encoded. As out-

lined earlier, memory performance might also benefit from testing at shorter

delays provided that the test trial(s) are followed by a restudy trial (Pyc &

Rawson, 2012). In this case, testing may enhance the subsequent re-encoding

of information (indirect testing effect; Izawa, 1966). However, these direct and

indirect testing effects often co-occur and can be difficult to separate in a mul-

titrial learning paradigm.

The main aim of this study was to substantiate the direct testing effect for

verbally encoded action phrases in Study I with the study type manipulated

within subjects and to examine whether the recall type (noun-cued recall of

verbs vs. verb-cued recall of nouns) affects the size of the testing effect. I

hypothesized that testing via cued recall strengthens the verb–noun relation

more than study-only and predicted the occurrence of a testing effect. If testing

with both the recall types engenders an equal amount of verb–noun relational

processing, the direct testing effects should have a similar size.

A secondary, more exploratory aim was to examine the indirect testing ef-

fect for both the recall types. To isolate the indirect from the direct effects of

testing, I conducted conditional analyses. I decomposed the recall perfor-

mance of the post-restudy tests into items that were newly retrieved and those

that were retained from the pre-restudy tests (Arnold & McDermott, 2013b).

A differential amount of new learning between the recall types would indicate

that the indirect testing effect occurs and its size differs for noun- versus verb-

cued recall.

Method

The final convenience sample consisted of 31 Swedish participants (age M

[SD] = 25.65 [5.96]; range = 18–42 years; 22 females and 9 males). Four ad-

ditional participants were recruited but were excluded from the analyses as

incomplete data were obtained. The experimental procedure was similar to

45

Study I. The participants learned 40 action phrases (i.e., verb–noun) by read-

ing them aloud. Half the action phrases were repeatedly studied throughout

the six learning trials (study-only condition), whereas the other half were

learned and cued-recalled in an alternating order (study–test condition). Each

learning trial was separated by a 30-s arithmetic filler task. This learning phase

was followed by two final cued-recall tests, one given after 2 min (short RI)

and the other after 1 week (long RI). During the intermediate and final recall

tests, I implemented either noun-cued recall (i.e., the noun was provided to

retrieve the verb) or verb-cued recall (i.e., the verb was provided to retrieve

the noun).

A 2 × 2 × 2 mixed-factorial design was applied. Recall type was manipu-

lated between subjects, with 15 participants (11 of whom were women) re-

ceiving verb-cued recall and 16 participants (11 of whom were women) re-

ceiving noun-cued recall. The participants were randomly assigned to both

recall-type conditions with the restriction that gender was counterbalanced.

Retention interval, or RI, (short vs. long) and study type (study-only vs. study–

test) were manipulated within subjects to increase power.

Results

A main finding was the reliable testing effect for verbally encoded action

phrases (see Figure 3). That is, repeated study–test practice reduced the rate

of forgetting relative to study-only practice, as indicated by a significant

interaction effect between the study type and RI.

A Verb-Cued Recall B Noun-Cued Recall

Figure 3. Final recall performance (mean proportion correct) for the 40 verbally en-

coded action phrases as a function of study type (study-only/study–test) and retention

interval (short/long), separately shown for verb-cued recall (Panel A) and noun-cued

recall (Panel B). Error bars represent standard errors of the mean (SEs).

46

This testing effect had a similar size for both recall types in terms of the

rate of forgetting. Furthermore, study–test items were better recalled than

study-only items across RIs, as indicated by a main effect of the study type.

This testing effect on overall memory performance was increased for noun-

cued recall—a finding that may stem in part from the indirect testing effect

during the learning phase.

The other main finding relates to the indirect testing effect with action

phrases, which was moderated in size by recall type. First, I observed that the

learning rate increased for noun- as compared with verb-cued recall; however,

this was observed only for the post-tests of the Initial Study and Restudy 1, as

can be seen in Figure 4.

Figure 4. Learning curves. Recall performance (mean proportion correct) on the post-

tests of Initial Study, Restudy 1, and Restudy 2 as a function of recall type (verb-

cued/noun-cued).

Second, this difference in the learning rate early in the learning phase was

related to an increased number of items that were newly retrieved from the

pre- to post-restudy tests of Restudy 1. However, the number of retained items

was equivalent across the recall types. The amount of newly retrieved and

retained items for Restudy 2 were comparable across the recall types. I

observed these findings even when adjusting for the available number of items

that were newly learned or retained (see Figure 5).

47

A Newly Retrieved Targets B Retained Targets

Figure 5. Panel A: Newly retrieved targets. Number of targets that were not retrieved

on the pre-test but were retrieved on the post-test of Restudies 1 and 2 as a function

of recall type (noun-cued/verb-cued). For Restudies 1 and 2, means are adjusted sep-

arately for the number of targets available to be newly retrieved during restudy. Panel

B: Retained targets. Number of targets that were retrieved on pre- and post-tests of

Restudies 1 and 2 as a function of the recall type (noun-cued/verb-cued). For Res-

tudies 1 and 2, means are adjusted separately for the number of targets available to be

retained during restudy. Error bars represent standard errors of the mean (SEs).

Conclusions

Repeated study–test practice reduced the rate of forgetting and enhanced long-

term retention, relative to study-only practice. This finding confirms the find-

ings of Study I and supports the notion that testing directly strengthened the

verb–noun relation within action phrases (Kubik, Söderlund et al., 2014; Pe-

terson & Mulligan, 2013). However, as the type of recall did not moderate the

size of this testing effect, the degree of verb–noun relational processing seems

to be similar across the recall types.

Testing also enhanced the subsequent recall performance indirectly by en-

hancing the subsequent restudy of verbally encoded action phrases. This indi-

rect testing effect was asymmetrically increased in favor of noun-cued recall

of verbs. These findings were explained by the notion that during recall, the

cues are tagged with regard to their recall status. During restudy, these tags

may be retrieved (Vestergren & Nyberg, 2014), and the learners are reminded

about the prior retrieval episodes (Nelson et al., 2013). I reasoned that as nouns

are more stable and concrete, they may be better recognized as prior retrieval

cues during restudy and may provide more reliable information about the re-

call status of items. This, in turn, may increase the chance of the action phrases

(related to the noun cue) to receive enhanced re-encoding. Additionally, un-

successful recall of verbs—the central components of the action phrase—may

be more salient than not recalling the noun; therefore, the respective action

phrases receive more effective re-encoding.

48

Together, the direct and indirect testing effects have contributed to the test-

ing benefit on overall memory performance, which was increased for noun-

cued recall. As a future step, it is important to investigate both the testing ef-

fects with enacted action phrases as a function of the recall type. It was ex-

pected that the direct testing effect would not occur after enactive encoding

irrespective of whether the study type is manipulated within subjects and test-

ing is implemented with either verb- or noun-cued recall. In contrast, the in-

direct testing effect on subsequent re-encoding should also be existent for en-

acted phrases and increased for noun-cued recall.

49

Study III

Kubik, V., Nilsson, L.-G., Olofsson, J. K., & Jönsson, F. U. (2014a). Putting

action memory to the test: Testing affects subsequent restudy but not long-

term forgetting of action events. Manuscript submitted for publication.

Objective

The objective of Study III was to examine the direct and indirect effects of

testing on cued recall for enactively encoded action phrases (i.e., SPTs) and

how they are affected by the type of recall.

Background

Study II demonstrated that the indirect testing effect occurred for verbally en-

coded action phrases and, importantly, that it was asymmetrically enhanced

in favor of noun-cued recall of verbs. Although we usually remember the ac-

tions in our daily lives, no study has yet investigated test-potentiated learning

for performed actions. Thus, Study III aimed to examine the indirect testing

effects on the subsequent learning of performed actions and investigate

whether they are asymmetrical with respect to recall type. As reasoned in

Study II, if nouns provide more reliable information about the recall status of

actions during restudy, I predicted an increased indirect testing effect for

noun-cued recall of actions.

Although the direct testing effect has been robustly demonstrated with var-

ious learning materials, I did not observe a test-related decrease in the rate of

forgetting with cued recall of enacted action phrases (Study I; Kubik, Söder-

lund et al., 2014). A main aim of the present study was to substantiate this

finding by manipulating study type within subjects and examine the testing

effect with two recall types: noun-cued recall of verbs and verb-cued recall of

nouns. If testing with both recall types elicits a similar amount of verb–noun

relational processing, I predicted no testing effect irrespective of the recall

type.

Method

The final sample consisted of 32 Swedish-speaking participants (age M [SD]

= 24.75 [6.22]; range = 16–42 years; 21 women and 11 men). Two additional

participants were recruited but were excluded from the analyses as only in-

complete data were obtained. The design, materials, and procedure were iden-

tical to Study II, with the exception of encoding type. In Study III, participants

enacted the action phrases instead of saying them aloud. Specifically, they

50

motorically performed the actions described in the verb–noun phrases dis-

played on the screen without any action-related object at hand. A 2 × 2 × 2

mixed-factorial design was applied, with RI (short vs. long) and study type

(study-only vs. study–test) as within-subjects factors. Recall type was manip-

ulated between subjects, with 16 participants (11 of whom were women) re-

ceiving verb-cued recall of nouns and 16 participants (10 of whom were

women) receiving noun-cued recall of verbs. Participants were randomly as-

signed to both the recall-type conditions with the restriction that a similar gen-

der distribution should be achieved.

Results

A main finding of this study pertains to the indirect testing effect. The results

suggested that the indirect testing effect occurred for enactive encoding and,

importantly, that it was moderated by recall type. First, the learning rate was

accelerated with noun-cued recall of verbs early in the learning phase. Though

the recall performance was similar on the first intermediate test, the recall per-

formance across intermediate tests increased more for noun-cued recall in the

succeeding tests (Figure 6).

Figure 6. Learning curves (mean proportions correct and standard errors of the mean,

SEs) are displayed as a function of post-tests (of Initial Study/Restudy-1/Restudy-2)

and recall type (noun-cued/verb-cued).

Second, the number of newly learned items during Restudy 1 (though not

Restudy 2) was increased for noun-cued recall, while the number of retained

items between pre- and post-tests of Restudies 1 and 2 was equivalent across

recall types. These results were robustly obtained even when adjusting for the

available amount of newly retrievable/retainable items (Figure 7). Together,

this result pattern suggests that noun-cued recall of verbs engenders a larger

indirect testing effect compared with verb-cued recall of nouns.

51

A Newly Retrieved Targets B Retained Targets

Figure 7. Conditional recall performance of the post-restudy tests (adjusted means

and SEs). Panel A: Number of newly learned targets on the post-tests of Restudies 1

and 2 are shown as a function of recall type (noun-cued/verb-cued), adjusted for the

number of targets available to be newly learned during restudy. Panel B: Number of

retained targets on the post-tests of Restudies 1 and 2 as a function of recall type,

adjusted for the number of targets available to be retained.

The other main finding pertains to the direct effect on final recall perfor-

mance. As can be seen in Figure 8, repeated study–test practice did not reduce

the rate of forgetting relative to study-only practice.

A Verb-Cued Recall of Nouns B Noun-Cued Recall of Verbs

Figure 8. Final recall performance (mean proportions correct and SEs) for the 40 en-

actively encoded action phrases as a function of study type (study-only/study–test)

and retention interval (short/long). Panel A: Verb-cued recall (means and SEs). Panel

B: Noun-cued recall (means and SEs).

52

Thus, the direct testing effect was not observed in terms of reducing the

rate of forgetting, neither with noun-cued recall of verbs nor with verb-cued

recall of nouns. However, a testing effect occurred in terms of a general

memory advantage for study–test items on final recall performance. This

overall testing effect was moderated by the recall type and was only reliable

for noun-cued recall of verbs.

Conclusions

Testing enhanced subsequent re-encoding of enacted action phrases during

the first restudy trial, and this indirect testing effect increased when the tests

included noun-cued recall of verbs. These results support the notion that nouns

may provide more reliable information regarding the recall status during res-

tudy or alternatively that verbs produce a stronger tagging of the associated

nouns, which then become more salient during restudy. Either way, the

chances for action phrases to receive enhanced re-encoding increase to the

extent that one of these mechanisms is activated (Vestergren & Nyberg,

2014), specifically when the phrases were previously not recalled (Nelson et

al., 2013).

Repeated study–test practice did not reduce the rate of forgetting of per-

formed actions, irrespective of recall type. These findings substantiate the re-

sults of Study I and extend them to another study design as well as to another

recall type (i.e., noun-cued recall). They are congruent with the view that in-

terleaved testing increased the verb–noun relation to a similar degree for both

recall types.

Furthermore, there was an overall testing benefit for the final recall perfor-

mance, which was reliable for noun-cued recall but not verb-cued recall. This

finding stems largely from the indirect testing effect, because the direct testing

effect was not reliable in terms of reducing the rate of forgetting over a period

of 1 week, and retention across learning trials was equivalent between the re-

call types.

53

General Discussion

The aim of this doctoral thesis was to study the effects of testing (via study–

test practice) and encoding (via enactment) on learning and memory with ac-

tion phrases, an ecologically valid material. I used action-phrase materials

(i.e., verb–noun phrases such as “water the flowers”) because they mimic the

basic aspects of everyday actions. Of particular interest was to investigate the

effects of interleaved testing on the rate of forgetting (i.e., the direct testing

effect) and on subsequent restudy (i.e., the indirect testing effect) as well as

how the type of recall (noun- vs. verb-cued) moderates these testing effects.

In combination, the facilitative effects of encoding through motor enactment

were investigated on memory relative to verbal encoding (i.e., the enactment

effect).

In the following sections, I will discuss the main results from the three em-

pirical studies along the themes of the testing effects and enactment effect.

Subsequently, I will outline several challenges and directions for future re-

search related to these themes before concluding with the final remarks.

Testing Effects

Although in our daily lives, we are often concerned with remembering per-

formed and still to-be-performed actions, the facilitative effects of testing

have not previously been investigated with action-relevant information. To

this end, in Studies I–III, I investigated the effects of testing with action

phrases, after both verbal and enactive encoding.

I will first report and discuss the direct testing effect on the rate of forget-

ting, following which I will discuss the indirect testing effect on the subse-

quent restudy of action phrases.

Direct Testing Effect

Studies I–III demonstrated the existence of a direct testing effect for action

phrases. That is, interleaved testing reduced the rate of forgetting over a 1-

week interval, compared to study only, and thereby enhanced long-term re-

tention. However, the testing effect was only observed for verbal encoding

(Studies I and II) and not for enactive encoding (Studies I and III). This results

pattern was found when both study types (i.e., study-only vs. study–test) were

manipulated between subjects (Study I) and within subjects (Studies II and

54

III). In addition, the type of recall (noun-cued recall of verbs vs. verb-cued

recall of nouns) did not affect the size of the testing effect for either verbal

encoding (Study II) or enactive encoding (Study III).

The present thesis extended the testing effect to action phrases, supporting

its robustness across learning materials (Roediger & Butler, 2010). I hypoth-

esized that testing by means of cued recall enhances verb–noun relational pro-

cessing if the retrieval attempt was successful. Recent research supports this

notion. Retrieval practice led to a testing effect when the final test was cued

recall (Peterson & Mulligan, 2013)—a memory test mainly relying on the

cue–target association strength (Peterson & Mulligan, 2013; Steffens et al.,

2009). It has also been suggested that successfully recalling items activates

more semantic mediators in the cue-related network compared to restudy prac-

tice and that these mediators may link cue and target more strongly together

and, in turn, support later retrieval of the target (Carpenter, 2009, 2011). Alt-

hough such semantic mediation of the cue–target relation may be a potential

mechanism underlying memory for action phrases, it may be a more realistic

scenario in other types of learning materials, such as noun pairs. In simple

action phrases (e.g., “lift the glass”), the verb and noun are, rather, directly

related: the verb specifies a concrete action (“water”) that can be directly per-

formed with the imagined object denoted by the noun (“the flowers”).

Given that motor enactment of action phrases should already promote effi-

cient verb–noun relational processing (Kormi-Nouri, 1995; Steffens et al.,

2009), I hypothesized that this binding mechanism can only be marginally, if

at all, enhanced through testing. In line with this notion, a direct testing effect,

in terms of the rate of forgetting, was observed only for verbal encoding (Stud-

ies I and II) but not for enactive encoding (Studies I and III), irrespective of

the design status of study type (within- vs. between-subjects). Thus, enact-

ment and testing engendered nonadditive effects on the rate of forgetting (For

potential statistical and design-specific qualifications, see section Methodo-

logical Challenges.). This results pattern is congruent with the observation

that several other well-known memory-enhancing phenomena have not been

observed for enactive encoding. Of particular relevance is the fact that gener-

ating additional information (e.g., producing a verb for the available noun)

also does not improve retention beyond the effect of enactment (Nilsson &

Cohen, 1988). This generation effect shares procedural similarities with the

testing effect as the generation of associates to a cue can be viewed as retrieval

practice from semantic memory. Generation and testing (by cued recall) show

similar facilitative effects on memory (Burns, 1990, 1992; Carrier & Pashler,

1992; Mulligan & Peterson, 2014; Peterson & Mulligan, 2013). Furthermore,

they are both assumed to enhance cue–target relational and item-specific pro-

cessing, though not inter-item relational processing (generation effect,

Bertsch et al., 2007; McDaniel & Bugg, 2008; testing effect, Karpicke & Za-

romb, 2010; Peterson & Mulligan, 2013), similar to enactment (Steffens et al.,

2009). However, repeated testing seems to facilitate item-specific processing

to a larger extent than repeated study or item generation (Karpicke & Zaromb,

55

2010) and can enhance inter-item relational processing when testing is imple-

mented via free recall (Zaromb & Roediger, 2010; Congleton & Rajaram,

2012). A notable difference between generation and testing may be that the

latter involves retrieving information from episodic memory through an in-

tentional retrieval mode to consciously reconstruct the past (Karpicke & Za-

romb, 2010).

The results of Studies II and III indicated that the type of recall did not

moderate the size of the testing effect. For verbal encoding (Study II), testing

reduced the rate of forgetting to a similar degree for both recall types, and for

enactive encoding, no testing effect emerged for either recall type (Study III).

Due to the relatively small sample sizes in Studies II and III, I could not ex-

clude the possibility that the lack of influence of recall type was due to low

power. However, additional analyses of the combined datasets of Studies II

and III (N = 63) confirmed that the influence of recall type on the testing effect

was negligible (ω̂G2 < .01). This pattern of results is congruent with the notion

that testing via noun-cued recall of verbs engages verb–noun relational pro-

cessing to a similar degree as verb-cued recall of nouns. The verb–noun asso-

ciation has been potentially strengthened in different directions or alterna-

tively in both directions when testing with noun- versus verb-cued recall. The

latter possibility accords with the finding that testing via cued recall enhanced

the retention of word pairs (e.g., “train–plane”) more than restudy, irrespec-

tive of whether memory in the final test was assessed in the same recall direc-

tion (“train – ?”) or the opposite direction (“? – plane”; Carpenter, Pashler, &

Vul, 2006). However, as the recall types were always congruent between the

intermediate tests in the learning phase and the final tests in the retrieval phase

of Studies I–III, the present thesis design could not answer this research ques-

tion.

In sum, I argue that the successful cued recall of information enriches the

memory trace of the action phrase in the form of cue–target relational pro-

cessing (Hunt, 2006; Karpicke & Zaromb, 2010). The notion that successful

recall constrains memory search to the correct targets (Karpicke et al., 2014;

Thomas & McDaniel, 2013) cannot be excluded given the relatively high final

recall performance and the experimental design of Studies I–III. They will be

further discussed in the section “Theoretical Challenges.”

Indirect Testing Effect

In addition to the direct effect, testing also facilitates re-encoding of previ-

ously unrecalled items when a subsequent restudy opportunity is given. As

testing was implemented via repeated study–test practice, I was also able to

examine this indirect testing effect (Arnold & McDermott, 2013a, b; Izawa,

1966).

The results showed that memory performance was equivalent for the two

study types (Studies I–III) or even increased in favor of study–test items

(noun-cued recall condition in Study III) after the short retention interval. This

56

finding provides some evidence that the indirect testing effect occurred for

action phrases, as study–test items—due to unsuccessful recall attempts at the

intermediate tests—were less exposed than study-only items during the learn-

ing phase. Only if the re-encoding of nonrecalled items is enhanced through

prior testing, study–test items can compensate for the fewer restudy occasions.

This interpretation is supported by the fact that recall retention across learning

trials was very high. Even though the direct testing effect may contribute to

final recall performance by enhancing the retention of successfully recalled

items, its mnemonic effect primarily unfolds across longer delays. This inter-

pretation is congruent with previous research showing that after shorter de-

lays, repeated study–test practice leads to equivalent or increased memory

performance relative to restudy practice (Arnold & McDermott, 2013b; Kar-

picke, 2009; Pyc & Rawson, 2012; Vestergren & Nyberg, 2014) and clearly

surpasses repeated testing without subsequent restudy, as the latter condition

only relies on the direct testing effect (Karpicke & Roediger, 2007).

In addition, the learning rate was accelerated for noun-cued recall of verbs

for verbal (Study II) and enactive encoding (Study III) due to more items be-

ing newly learned during Restudy 1. The number of retained items, however,

was equally high for both recall types. This differential amount of new learn-

ing during Restudy 1 provides evidence for the indirect testing effect, at least

following noun-cued recall, and its effectiveness to facilitate subsequent

learning varies with recall type. I draw this conclusion because prior recall

performance, during the first intermediate test, was similar for the two recall

types. Furthermore, item retention between the intermediate tests did not vary

across recall types—a finding that reflects, in part, the direct testing effect

(Arnold & McDermott, 2013b). The increased indirect testing effect for noun-

cued recall largely contributed to the test-related benefit in final memory per-

formance, which was only reliable for noun- but not verb-cued recall in Stud-

ies I–III.

Together, the indirect testing effect was generalized to action-phrase mate-

rial for both enactive and verbal encoding, but it was asymmetric with regard

to recall type. These findings complement previous research that more directly

manipulated the magnitude of the indirect testing effect. For example, when

varying the number of testing rounds preceding the restudy trial, it was ob-

served that the size of the indirect testing effect (i.e., the amount of new learn-

ing during testing ensuing restudy) increased the more pre-restudy testing

rounds were given (Arnold & McDermott, 2013b). Convincing evidence for

the indirect testing effect was also provided by Arnold and McDermott

(2013a) who manipulated both the availability of tests before restudy and the

availability of a restudy opportunity. They observed that the benefit of restudy

increased with previous testing as compared to no pre-testing. The present

thesis expanded upon these findings by demonstrating that even the type of

recall on a single pre-restudy test can affect its potency to enhance subsequent

encoding of action phrases.

57

Although several studies have addressed the indirect testing effect, its un-

derlying mechanisms remain unclear. Vestergren and Nyberg (2014) sug-

gested that the indirect testing effect may rely in part on automatically tagging

the cue item of the tested pair associates during pre-restudy recall. Paired as-

sociates then become more salient during restudy when the cue items are rec-

ognized as previous retrieval probes and their associated tags are retrieved. In

addition, Nelson et al. (2013) demonstrated that the amount of new learning

was positively associated with retrieval processes during restudy, which may

involuntarily remind the learner of unsuccessful retrieval attempts. Together,

these mechanisms may then initiate an enhanced re-encoding of tested items.

The cue items during the restudy of the verb–noun phrase may play a sig-

nificant role if the indirect testing effect primarily applies to items for which

the target was not recalled. As nouns are semantically more stable and recog-

nizable than verbs (Earles & Kersten, 2000; Kersten & Earles, 2004), I rea-

soned that nouns as retrieval cues should provide more reliable information

about the associated (unsuccessful) recall status during restudy. This, in turn,

may engender more effective re-encoding of the target items. The finding that

the relative amount of new learning following noun-cued recall of verbs in-

creased during Restudy 1 supports my hypothesis and indicates an increased

indirect testing effect compared to the verb-cued recall of nouns. Furthermore,

the unsuccessful retrieval of verb targets during noun-cued recall may produce

a stronger tag for the associated cues than the unsuccessful retrieval of nouns

because verbs constitute the main component in action phrases (Kersten &

Earles, 2004). The more salient cue tags for nouns may function as stronger

reminders of unsuccessful retrieval episodes and also initiate enhanced re-en-

coding during restudy (Nelson et al., 2013; Vestergren & Nyberg, 2014).

In sum, the indirect testing effect was generalized to action-phrase material

for both encoding conditions and, critically, was moderated by recall type.

One explanation pertains to the retrieval cue, which may function during res-

tudy as a reminder of previous retrieval attempts and, in turn, influence the

amount or nature of subsequent re-encoding. To further the understanding of

the indirect testing effect in action-phrase material, future research should

more directly manipulate the possibility and amount of test-potentiated learn-

ing and create a pool of action phrases for which the characteristics of their

single component—noun, verb, and directive association strength—are better

controlled, as discussed in the section “Methodological Challenges.”

Enactment Effect

The present results speak to the relative mnemonic efficacy of verbal and en-

active encoding. As cued recall was used in the included studies, I predicted

a reliable enactment effect based on the notion that enactment promotes verb–

noun relational processing. The results supported this prediction. In Study I,

58

enactment facilitated final cued-recall more than verbal encoding after both

retention intervals. This result was corroborated when Study II (verbal encod-

ing) was compared to Study III (enactive encoding) regarding final recall per-

formance; a robust enactment effect emerged across the studies, supporting

previous findings (Kormi-Nouri, 1995; Steffens et al., 2009; Svensson & Nils-

son, 1989). This cross-study comparison is internally valid, as the participants

were randomly attributed to studies, and the participants’ characteristics were

equivalent among them. The results extend those of prior studies, as the en-

actment effect is typically examined in single-trial paradigms including only

one study trial and one ensuing test trial. However, the included studies

demonstrated the enactment effect even for the final cued-recall tests follow-

ing a multitrial learning phase. Only a few studies investigated the learning of

action phrases across multiple trials, mainly including free-recall tests. These

studies indicated that the enactment effect attenuated over the learning session

with action-phrase material that can be clustered along various pre-experi-

mental categories (Koriat & Pearlman-Avnion, 2003; Koriat, Pearlman-

Avnion, & Ben-Zur, 1998) and was even absent for independent action

phrases (Kubik et al., 2014). The discrepancy between the present and previ-

ous results might thus be explained by the additional reliance of free recall on

inter-item relational processing—a mechanism that is not enhanced by enact-

ment, specifically not for independent action phrases (Steffens et al., 2006,

2009). To examine the size and progression of the enactment effect in cued

recall during the learning phase, I conducted additional analyses for Study I

and the combined Studies II and III. A reliable enactment effect was revealed

for the first intermediate test. Even though the enactment effect decreased in

size over the learning phase, it remained reliable across all the tests that fol-

lowed. Thus, this encoding effect seems to be more robust in cued than in free

recall, conceivably because the memory test mainly taps the processing of the

verb–noun relation, which is strongly enhanced by enactment (Kormi-Nouri,

1995; Steffens et al., 2006, 2009).

Critically, Study I also investigated how far enactment influenced the rate

of forgetting over a 1-week retention interval. Only one study addressed this

issue more systematically for longer retention intervals (2 days, 1 week; Nils-

son et al., 1989) and observed that action phrases were forgotten at similar

rates after verbal and enactive encoding. However, these findings may be af-

fected by the tests, which were interleaved after each list to be learned during

the learning phase. These additional tests may have reduced the rate of forget-

ting more for verbal than for enactive encoding and potentially obscured any

differences in the rate of forgetting between encoding conditions. In the in-

cluded studies, I tested this possibility by manipulating study type (repeated

study-only vs. study–test practice). Confirming previous research, the results

showed that while enactment did not reduce the rate of forgetting in the study–

test conditions, it did so in the study-only conditions. Additional, cross-exper-

imental analyses of Studies II and III revealed equivalent results and con-

firmed the results of Study I. Thus, interleaved testing obviated the finding

59

that enactment reduced the forgetting of action phrases relative to verbal en-

coding. This results pattern supported our hypothesis that motor enactment

and testing via successful recall may both elicit verb–noun relational pro-

cessing—a binding mechanism that is supposed to reduce the rate of forget-

ting in cued recall over time. This finding does not accommodate the obser-

vation that no encoding variable reduces the rate of forgetting (Slamecka &

McElree, 1983).

Two caveats that may have influenced the results should be noted. First,

the two encoding conditions produced different initial recall levels after the

short retention interval, which may have influenced the rate of forgetting.

However, enactment reduced the rate of forgetting exclusively in the study-

only conditions even though initial recall levels were equivalent across study

types. Second, the rate of forgetting was assessed by repeated tests, and there-

fore, the effect of forgetting over time may be confounded by testing effects

and generally reduced. However, this circumstance should rather strengthen

our conclusions, as the final test after the short delay may have likely reduced

the rate of forgetting more for verbal than for enactive encoding. Given these

limitations, the reported results suggest that enactment does reduce the rate of

forgetting over time. However, further research should explore whether these

findings generalize to experimental designs in which longer retention intervals

are given, or initial recall levels are lower or equalized across encoding con-

ditions.

Overall, in the present studies, the enactment effect surpassed the (direct

and indirect) effects of testing in enhancing short- and long-term retention.

Furthermore, combining the two study techniques resulted in superior cued-

recall performance than testing alone but not than enactment alone. Thus, en-

actment maximizes long-term learning beyond the effects of testing, even

though they have similar and nonadditive effects on the rate of forgetting.

These findings, however, may rely on the fact that not all action phrases were

successfully recalled and benefitted from retrieval processing. Other imple-

mentations of testing—for example, testing with feedback—may be equally

or even more effective in enhancing long-term learning than enactment.

In the included studies, I did not provide any real objects (denoted by the

nouns) during learning for either encoding condition. For this reason, the mne-

monic benefits of enactment in Studies I–III can be merely attributed to mo-

torically performing the item material and not to any effects related to objects.

Even though providing objects would further enhance the ecological validity

of the learning materials, it may confound the facilitating effects associated

with enactment and object presence, specifically if objects are exclusively

given for enactive encoding. Importantly, a verbal control condition was in-

stantiated by asking participants to read the action phrases aloud. This vocal

production of action phrases can be viewed as a conservative control condition

because it facilitates later memory performance, particularly in cued recall and

recognition, relative to the silent reading of items (MacLeod et al., 2010). This

production effect has also been explained in terms of increased item-specific

60

and cue–target relational processing. Based on this assumption, the data in the

present thesis suggest that enactment—viewed as a motoric production of ac-

tions—is even more effective than vocal production as it probably engages

the same item-specific mechanism(s) to a higher degree than in vocal produc-

tion. Thus, even increased mnemonic benefits of enactment are expected when

silent reading is used as the control condition.

In sum, the research reported in the present thesis began from the currently

dominant item-specific relational framework in action memory (Kubik,

Söderlund et al., submitted; Peterson & Mulligan, 2010; Schult et al., 2014),

which also successfully explains other encoding phenomena, such as the pro-

duction effect, generation effect, enactment effect, and recently, the testing

effect. The predictions of this framework for the current thesis were largely

confirmed. An enactment effect was revealed in that intermediate and final

memory performance were substantially increased and the rate of forgetting

reduced (for study-only conditions), suggesting enhanced processing of the

verb–noun relation by enactment (Kormi-Nouri, 1995; Steffens et al., 2009).

Similarly, interleaved testing reduced the rate of forgetting for verbal but not

enactive encoding, providing evidence that both study techniques exhibit non-

additive effects on the rate of forgetting and may rely in part on the same

mechanism.

Alternative Memory-Strength Explanation

The findings of Studies I–III can be alternatively interpreted in terms of the

bifurcated distribution model (Halamish & Bjork, 2011; Kornell et al., 2011).

According to this model, forgetting only appears to be mitigated by testing

and can instead be explained by the different distribution or amount of

memory strength for both study types. Successfully recalled items gain more

in memory strength than studied items while nonrecalled items do not gain at

all in memory strength (Halamish & Bjork, 2011; Kornell et al., 2011). Due

to test-potentiated learning, specifically these nonrecalled items can receive

more effective re-encoding and memory strength during subsequent restudy

than study-only items, and additionally when being successfully recalled on

the post-restudy test. A difference in the resultant item strength between the

study types can then explain the observed testing effect, even when we assume

equal rates of forgetting. The equivalent memory performance after shorter

retention intervals reflects the same amount of study-only and study–test items

above the critical memory threshold. The long-term advantage for study–test

conditions results from the increased average memory strength for study–test

items. They reside more likely above the threshold despite an eventual de-

crease in memory strength with time.

Similarly, the enactment effect can be explained by this account. Both en-

acted and verbally encoded items should produce normal item strength distri-

butions whereby the distribution for enacted items would be shifted further

61

upwards. The increased number of enacted phrases above the threshold leads

to a better recall performance while the increased memory strength following

enactment leaves more items above the threshold as memory strength de-

creases with time. Thus, although the rates of forgetting were similar, the en-

actment effect increased over the retention interval. However, it should be

noted that due to the increased recall level after enactive encoding, retrieval

was perhaps “undesirably” easier than after verbal encoding, and this de-

creased retrieval difficulty may have reduced the relative gain in memory

strength for testing enacted phrases.

When combining testing and enactment, no additive effects on the rate of

forgetting were observed. Due to the bifurcated-distribution model, combin-

ing testing and enactment may lead to a larger increase in memory strength

than when considering each of the study techniques alone. However, this dif-

ference in memory strength may not be revealed as many items are too far

away from the memory threshold. Based on the distribution model, I would

expect that with longer retention intervals or a lower recall level, a testing

effect would occur for enacted items and an enactment-related decrease would

occur in the rate of forgetting for study–test items. Without any restudy trials

following the interleaved tests, the distribution of memory strength should

also be bifurcated for enacted phrases (i.e., recalled, but not unrecalled, items

gain in memory strength) and thus lead to a typical cross-over interaction be-

tween study type and retention interval. Such an experimental design would

provide more conclusive evidence about the direct testing effect with action-

phrase material by preventing the possibility of test-potentiated learning. On-

going research investigates these predictions of the bifurcated-distribution

model.

62

Challenges and Directions for Future Research

The present thesis provides a starting point to the investigation of the effects

of testing and motor enactment with action-phrase material. In the following

sections, I will outline the methodological, theoretical, and practical chal-

lenges for future research on this topic.

Methodological Challenges

In this section, I will highlight the design features of Studies I–III that require

a more thorough discussion. This discussion is aimed at providing suggestions

for future research to overcome potential methodological shortcomings and to

further the understanding of the mechanisms underlying the effects of testing

and enactment on memory.

Isolating Direct and Indirect Testing Effects

All included studies applied a multitrial learning paradigm, involving both re-

peated restudy and repeated study–test practice. Since the test trials were fol-

lowed by restudy opportunities, both direct and indirect testing effects could

occur in combination. As recent research (Arnold & McDermott, 2013 a, b)

highlights the distinction between these two types of testing effects, I at-

tempted to disambiguate their specific contributions to learning and memory

of action-phrase material in the empirical studies. Future research would ben-

efit from isolating both testing effects—where relevant and to the extent pos-

sible—and studying them separately. This would allow us to uncover more

clearly their common and distinctive underpinnings.

Evidence for the indirect testing effect, at least for noun-cued recall, was

provided by the differential amount of new learning between recall types. In

addition, the finding that final recall was equivalent across study types or even

increased for study–test items—despite being less exposed during the learning

phase than study-only items—indicated the existence of the indirect testing

effect. However, this evidence may still be fairly indirect. An important next

step would be to effectively separate the distinctive contribution of the indirect

testing effect from the effect of successful retrieval and restudy. A plausible

step would be to manipulate both the availability of a restudy opportunity fol-

lowing testing (e.g., STST vs. ST–T) and the number of tests preceding the

63

restudy trial (e.g., STTST vs. STST vs. S–ST). Such a design would poten-

tially demonstrate the indirect testing effect beyond the facilitating effect of

restudy practice per se (without previous testing). The additional manipula-

tion of recall type would provide more direct evidence for the indirect testing

effect following verb-cued recall as well as confirm the differential effective-

ness between recall types to facilitate subsequent re-encoding. However, in

behavioral paradigms, the evidence for test-potentiated learning remains ra-

ther indirect by means of pre- and post-restudy recall analysis. Future research

examining neuroimaging may more directly investigate re-encoding during

restudy and further elucidate the key mechanism(s) involved. An important

area for future research is whether or not successfully recalled items also ben-

efit from test-potentiated learning, relative to restudy per se. A behavioral par-

adigm cannot easily adjudicate between these possibilities, as the relative

amount of new learning for nonrecalled items is the primary evidence for the

indirect testing effect. Thus, in the present thesis, the indirect testing effect

may have also occurred for the successfully tested items. Recent evidence

(Vestergren & Nyberg, 2014)—using functional magnetic resonance imag-

ing—suggests that irrespective of the previous recall status, tested items may

receive more focused attention during restudy, consequently initiating deeper

semantic processing and more associative binding between cue and target.

Another pertinent issue that can be explored in future research is to determine

the relationship between the indirect testing effect and the “indirect generation

effect.” That is, an unsuccessful attempt to generate the correct target (“tide–

?”) in a pre-test trial facilitates the subsequent encoding of the complete word

pair (“tide–beach”) during initial study (Grimaldi & Karpicke, 2012; Kornell,

2014; Kornell et al., 2009). Although both phenomena involve retrieval from

memory (episodic vs. semantic), the indirect generation effect does not gen-

eralize to unrelated word pairs (“beach–spoon”) or to experimental designs in

which initial study is delayed and given in a separate trial with many items

interleaved. Future research, including brain imaging, may explore the com-

mon as well as distinct processes underlying these different types of the indi-

rect “testing” effect.

The direct testing effect typically manifests in a cross-over interaction ef-

fect when no restudy opportunity follows testing. In other words, restudy prac-

tice leads to superior memory performance after the short retention interval,

but testing surpasses the latter in long-term retention. This classical testing

effect most likely results from the unbalanced re-exposure of items (i.e., re-

trieval success problem). The learner can process all items during restudy but

only successfully recalled items during testing. In that regard, restudy—and

every encoding manipulation—has an “unfair” advantage to begin with, and

the testing effect on long-term retention occurs only due to mitigated forget-

ting (or the increased memory strength for successful recall; Kornell et al.,

2011). In the present thesis, however, the testing effect did not emerge in the

form of a crossover interaction for the verbal encoding condition (butt see the

verb-cued recall condition in Study II for an exception). In fact, the testing

64

effect is revealed as a pronounced advantage in long-term retention while the

initial recall levels after the short delay were equivalent between study types,

or the test advantage was smaller. These noncrossover interactions are likely

due to the provision of restudy opportunities in the testing condition and the

possibility of test-potentiated learning, which together enhance the recall per-

formance for study–test items after the short retention interval. As the direct

testing effect most evidently affects the future retainability of successfully re-

called items, we analyzed this testing effect mainly in terms of the rate of

forgetting. The latter refers to the recall drop of previously retrieved items

with time and is arguably independent of the initial recall level (Slamecka &

McElree, 1983), which is strongly influenced by the indirect testing effect.

However, the possibility cannot be excluded that the rate of forgetting is also

affected by the indirect testing effect. Nevertheless, there is no clear evidence

yet for this possibility (Slamecka & Katsaiti, 1988). Previous research rather

suggests that test-potentiated learning diminishes the interaction effect be-

tween study type and retention interval and elevates the overall recall level in

keeping with the distribution model (Kornell et al., 2011). Future research in

action memory should further investigate the testing effect by attempting to

avoid the retrieval success problem. This would permit a fairer comparison

between the testing manipulation and other effective encoding manipulations,

such as motor enactment. One approach is to provide a re-encoding oppor-

tunity in a separate restudy trial, as was adopted in the included studies. Alt-

hough I ensured high and comparable levels of retrieval success across the

study types, it may still be argued that the learners re-experienced the study–

test items less (approximately 80%–90%) than the study-only items (100%)

in terms of processing time. Therefore, immediate restudy (i.e., feedback) may

be provided after every item on the cued-recall test (100%). In this way, all

items are processed to an equivalent amount even though some of them cannot

be recalled. However, both variants make it difficult to disambiguate the direct

and the indirect testing effects. An alternative approach is to ensure the suc-

cessful retrieval of all items by means of learning to criterion (Karpicke &

Roediger, 2007, 2008; Karpicke & Smith, 2012). That is, each tested item is

recalled at least once (before dropping it from learning) or all items from each

study type have been recalled at least once before implementing the restudy

or testing manipulation. This may even lead to a direct testing effect after

shorter delays (Karpicke et al., 2014). However, such a procedure—primarily

orientated to achieve a behavioral criterion—neglects the spacing of the study

and test events, which itself can foster involuntary retrieval attempts, (Greene,

1989). Furthermore, the underlying memory-strength distribution for both

study types becomes less predictable.

All the aforementioned approaches to tackle the retrieval-success problem

are associated with some methodological issues. To obtain greater clarity, I

would suggest that future research explore the testing effects with more than

one approach and examine whether or not the reported results pattern is ro-

bust. It should be noted, though, that manipulating the study type is never a

65

pure process. Retrieval can be initiated during restudy (specifically, when

spaced apart and mixed with test opportunities), and tests can be ineffective

in initiating retrieval practice, for example, when the answers to be given are

readily available (open-book tests; Agarwal, Karpicke, Kang, Roediger, &

McDermott, 2008).

Measuring Forgetting

A thorough investigation of the temporal course of forgetting is a complex

endeavor. Several factors may influence the course of forgetting.

First, to obtain a pure measure of forgetting, memory should be tested for

different groups of participants or sets of items at different points in time, as

assessing memory increases the future retrievability (of successfully recalled

items) at a subsequent point in time. In the present thesis, I measured forget-

ting by testing the memory for all participants and all items after the short and

long retention intervals. This repeated testing of items and persons at both

measurement points possibly reduced the effects of time on the later test

(Deese, 1958; Hanawalt, 1937). Although testing and time effects may be con-

founded, the repeated-testing design used in the included studies still allows

us to evaluate the relative amount of testing on the rate of forgetting, in other

words, to compare a single testing round (i.e., “study-only”: SSSSSST) versus

repeated testing rounds (i.e., study–test: STSTSTT). Further research may ad-

ditionally manipulate the retention interval between subjects (i.e., by testing

different groups at different points) and different sets of items to isolate the

effects of testing and time on memory and thereby to obtain purer measures

of forgetting.

Second, different measures of forgetting can lead to diverse results, as they

reflect the different properties of the retention curves (Wixted, 1990). In the

included studies, I analyzed the data in terms of both absolute forgetting

scores (testing the vertical distance of forgetting curves; Slamecka, 1985;

Slamecka & McElree 1983) and proportional forgetting scores (i.e., testing

the horizontal distance between forgetting curves, Loftus, 1978; 1985). With

both measures, equivalent results were obtained, supporting the reliability of

our conclusions.

Third, the heightened initial recall level after enactment (relative to verbal

encoding) may have influenced the rate of forgetting, rather than enactment

per se, an aspect that needs to be considered, depending on the chosen meas-

ure of forgetting (Wixted, 1990). Based on the test of vertical parallelism, var-

iations in the initial recall level do not affect the rate of forgetting (Slamecka

& Katsaiti, 1988). In this case, it can be concluded that enactment per se re-

duced long-term forgetting. Based on the test of horizontal parallelism, how-

ever, this conclusion cannot be drawn, as higher initial recall levels already

lead to reduced rates of forgetting (Loftus, 1985). As equivalent results were

obtained with both measures, I interpreted the interaction effect as an indicator

of forgetting. However, future research may also match the initial recall levels

66

between encoding types, for example, by increasing the number of item

presentations for verbal relative to enactive encoding (Nilsson et al., 1989).

Fourth, relatively high recall levels after the short retention interval were

achieved. This was true for the included studies, and may have two reasons:

first, to diminish the unequal re-exposure of items in restudy and test trials

and, second, to ensure strong direct testing effects that rely on successful re-

call. However, in particular, the recall levels after enactive encoding approxi-

mated the ceiling level, and therefore, the decrease in memory performance

may underestimate the actual amount of forgetting, even though a significant

enactment effect was demonstrated. It should be noted, though, that enactment

did not reduce the rate of forgetting for study–test items, which had an equiv-

alent initial recall level after the short retention interval as study-only items.

Nonetheless, future research should attempt to confirm the finding that enact-

ment reduces the rate of forgetting also on a lower performance level.

Fifth, observed differences in the rate of forgetting may be restricted to the

level of observed data (Slamecka, 1988). To draw conclusions regarding an

underlying psychological construct (e.g., strength of memory trace or forget-

ting), evidence of crossover interactions in the recall data are needed, as ob-

served recall probabilities and memory strength are nonlinearly related

(Loftus, 1985b; Wagenmakers, Krypotos, Criss, & Iversson; Wixted, 1990).

Translating recall probabilities to the scale of memory strength can remove

(i.e., transform away) noncrossover, but not crossover, interactions. Although

most interactions in the included studies did not cross over, the testing-effect

interactions nearly “touch” (for the short retention interval). Therefore, they

can be viewed as “borderline nonremovable interactions” (Wagenmakers et

al., 2012), and tentative conclusions regarding the psychological level can be

arrived at. Nonetheless, conclusions regarding memory strength or forgetting

can be drawn in the numerous cases for which the direct testing effect emerged

as a crossover interaction effect when testing was not followed by subsequent

restudy (Roediger & Karpicke, 2006b). Thus, as the ultimate aim is to under-

stand the underlying psychological processes, it is important to design exper-

imental studies in such a way that conclusions can be reached independent of

the measurement scale. In addition, future research should aim to describe the

mathematical form of forgetting curves following retrieval and restudy prac-

tice (Wixted, 1990). This more quantified approach provides parameters to

quantify the rate of forgetting (and the degree of initial learning) across mul-

tiple measurement points. Using such a method, Carpenter et al. (2008), for

example, assessed the rate of forgetting for testing (with immediate feedback)

versus restudy after 5 min, or 1, 2, 7, 14, or 42 days. Even in the absence of

an interaction effect between study type and retention interval, fitting a power

function to the data revealed that testing reduced the rate of forgetting. It re-

mains to be seen whether testing memory within subjects across multiple and

longer retention intervals (e.g., 2 min, 1 day, 1 week, 2 weeks, and 4 weeks)

resists direct testing effects for enacted action phrases.

67

Action Phrases—Asymmetric Learning Material

As action phrases consist of two different components, a verb (e.g., “wash”)

and a noun (e.g., “car”), they are inherently asymmetric, unlike common

learning material (e.g., noun–noun pairs). Consequently, across recall types,

the cue and the target vary at the same time, and thus, it is not possible to

separate the contributions of cue efficiency, target availability, and the

strength of the verb–noun association. With regard to the indirect testing ef-

fect, though, cues may play a significant role during the pre-restudy test and

the restudy trial. Only the cues (but not the targets) are available for unsuc-

cessfully recalled items; during restudy, they may provide reliable information

to the participant about the recall status and about the items that need effective

re-encoding. However, it may be argued that failed retrieval of the central verb

component results in a stronger tagging of the noun cue, which in turn helps

trigger enhanced re-encoding of that particular action phrase. The combined

effects of cue efficiency and target availability may enhance the indirect test-

ing effect specifically for noun-cued recall of verbs. For this reason, I refer to

this manipulation of noun-cued recall of verbs versus verb-cued recall of

nouns as two recall types, which imply the simultaneous change in cue and

target between them.

Future research may investigate the specific factors that determine how re-

call type affects testing. For example, in addition to action (i.e., verb–noun)

phrases, the testing effect should be examined also with verb–verb and noun–

noun phrases. This would allow to examine the influence of the cue (and the

search process afforded by the cue) on the testing effects by holding the target

constant, although this manipulation may affect verbal and enactive encoding

differently (Engelkamp, 1991; Helstrup, 1991). Furthermore, it would merit

research to provide normative data regarding the item characteristics of verbs,

nouns, and their associations, that is, the individual components of action

phrases. In addition to their grammatical classification, verbs and nouns differ

in their degree of concreteness (Kersten & Earles, 2004). Nouns—used in the

present thesis—are mainly basic level words, referring to single objects (e.g.,

“car”). Verbs, on the other hand, refer to broader categories of events and may

rather resemble superordinate nouns (e.g., “vehicle”; Kersten & Billman,

1997). Furthermore, the verb/noun order within action phrases may be influ-

ential. In the current thesis, I applied Swedish action phrases in which the verb

always precedes the noun. However, in other languages, the naturally given

word order is reversed such that the verb follows the noun (e.g., in German).

Finally, action phrases may differ in association strength from verb to noun

and vice versa. Although verb–noun association strength was previously

measured (item integration: Kormi-Nouri, 1995; Kormi-Nouri & Nilsson,

1998), the associative direction was neglected. Specifically, differences in

“forward” and “backward” associative strength may affect the moderating

role of recall type on the testing effects. In sum, further research should adju-

68

dicate the underlying factors pertaining to cue effectiveness, target availabil-

ity, and directive association strength when investigating testing effects with

the cued recall of action-phrase material.

Another venue of future research is to generalize testing effects further to

goal-directed action sequences in an attempt to approach more realistic fea-

tures of everyday activities than with simple action phrases. Goal-directed ac-

tion sequences comprise several component actions that are organized and

specified in terms of a goal and an outcome, for example, loading a dish-

washer, cleaning a window, etc., in the context of cleaning (Schult et al.,

2014).

Theoretical Challenges

To explain the effects of testing and enactment with one general account of

memory presents many challenges, though it may be a promising step to ef-

fectively understand the similarities, differences, and dependencies between

them. One of these theoretical challenges pertains to the various ways in

which testing can be implemented (e.g., free recall, cued recall, or recogni-

tion). Implementations of testing affect the efficacy and underlying mecha-

nisms of the testing effect. Another, theoretical challenge relates to the role of

the episodic context for the testing and enactment effects—an aspect of epi-

sodic memory representations, which has been rather neglected (Karpicke et

al., 2014). In this section, I will focus specifically on the direct testing effect

and enactment effect.

Multiple Implementations of Testing

The present thesis is mainly concerned with testing by means of cued recall

during the learning phase. This implementation of testing and motor enact-

ment enhances cue–target relational and item-specific processing, as both

these types of processing exhibit positive effects in final cued-recall tests (re-

liant on cue–target association) and final recognition tests (reliant on item-

specific information; Karpicke & Zaromb, 2010; Mulligan & Peterson, 2014;

Steffens et al., 2009). However, testing via cued recall and enactment do not

facilitate inter-item relational processing. For example, negative testing oc-

curred with final free recall, which is additionally reliant on inter-item rela-

tional information (Mulligan & Peterson, 2014), and the enactment effect, if

not presented with real objects (Kormi-Nouri, 1995), is of smaller size in free

recall than in other retrieval assessments (i.e., cued recall and recognition

tests; Kubik et al., 2014; Steffens et al., 2009).

However, testing can be implemented in various ways, and thereby, its un-

derlying mechanisms can vary. For example, if implemented by means of free

recall during the learning phase, testing can enhance encoding on inter-item

69

relational information (semantic associations between items: Congleton &

Rajaram, 2012; Zaromb & Roediger, 2010; temporal associations between

items: Lehman, Smith, & Karpicke, 2014). In contrast, motor enactment (i.e.,

in the absence of real objects) generally does not enhance the encoding of

inter-item relational information relative to verbal encoding (semantic associ-

ations: Engelkamp & Zimmer, 1996, 2002; temporal associations: Zimmer &

Engelkamp, 1989; idiosyncratic associations: Koriat & Pearlman-Avnion,

2003; Koriat, Pearlman-Avnion, & Ben-Zur, 1998 for increased enactive clus-

tering based on movement similarities). In sum, the degree to which enact-

ment and testing produce similar effects and share, in part, the same mecha-

nisms, depends on the specific ways in which testing is implemented. Thus,

the conclusions of the present thesis are fairly restricted to testing via cued

recall, which probably exhibits most similarities with the effects of enactment.

Other, less experimentally controlled testing formats, such as using flash

cards, quizzes, or short-answer tests, likely capitalize on multiple mecha-

nisms.

A Synthesis—An Item–Context Account

The effects of testing and enactment can be successfully explained in terms of

an item-specific—relational processing account. However, in my view, this

account might be more intuitively framed in terms of an item-context model.

In that way, both item events and the specific spatiotemporal context (e.g.,

“when,” “where,” learner’s mental state, inter-item relational information) re-

lated to each of them are encoded and stored in an episodic memory represen-

tation (Howard & Kahana, 2002; Lehman & Malmberg 2013).

As I hypothesized previously, testing and motor enactment likely share

mechanism(s) that strengthen the item representation (or memory trace) of an

action event. Both study techniques facilitate the encoding of item-specific

information (i.e., verb or noun) or cue–target relational information (i.e., the

verb–noun association), which makes the entire action phrase more discrimi-

nable from other action phrases. This enhanced strength and distinctiveness

of the underlying memory traces may result from the fact that semantic, mo-

toric, and/or multisensoric attributes are added to the item representations (en-

actment effect: Engelkamp, 2001; testing effect: Carpenter, 2009, 2011) and

thereby enrich the memory representation.

The spatiotemporal context is the other ingredient in the episodic memory

representation. The context changes (slightly) with time and events (Lehman

& Malmberg, 2013) and can be later used to guide the search process of the

target information, specifically when no other item cues are available during

retrieval. With exception to inter-item relational information, little attention

was devoted to the aspects of the episodic context (e.g., location and time of

the item event) and how they contribute to the mnemonic effects of testing

(Karpicke et al., 2014) and enactment (Koriat et al., 1991; Mecklenbräuker,

Steffens, Jelenec, & Goergens, 2011). This is surprising because episodic

70

memory in daily life is heavily dependent on context information. For exam-

ple, when we have performed a routinized activity, such as locking the apart-

ment door in the morning, we may remember an occurrence of this action

type, but we often are uncertain of whether we performed the action today.

Thus, to remember whether an event occurred at a specific time or space, we

need to encode and retrieve distinctive contextual features related to this epi-

sode.

I reason that both study techniques differ in the degree to which they can

capitalize on the episodic context. Enactment typically focuses attention on

performing the action, probably at the expense of encoding context infor-

mation and creating item-context associations (Koriat et al., 1991). Prior re-

search has shown that enactment does not enhance or even hamper the encod-

ing of source information (how the item was encoded; Hornstein & Mulligan,

2004), spatial context (Helstrup, 1987, 1989), or item-order information (Ol-

ofsson, 1996; Engelkamp & Dehn, 2000). However, the context is interac-

tively encoded when it becomes part of the performed actions, for example,

when real objects (denoted by the noun) are present (Mecklenbräuker et al.,

2011; Steffens et al., 2007). In contrast, during testing, learners use available

cues in the present context even when they are independent of the item event

and create item-context associations. For example, it has been shown that test-

ing via free recall enhances source memory during final recognition tests (dis-

criminating the list from which the particular items stemmed; Brewer et al.,

2010) and enhances retrieval when only the last out of several previously

learned item lists should be recalled (Szpunar et al., 2008). Recently, Karpicke

et al. (2014) suggested that when learners attempt to retrieve the target, they

use the available cues in the present context and, if needed, reinstate the prior

study context (i.e., context reinstatement and context encoding). Testing inte-

grates features from study and recall contexts to an updated context represen-

tation. The latter can serve as an effective cue in future retrieval situations and

can reduce the search set from retrieval candidates that are not associated with

specific context features (“episodic context account”; Karpicke et al., 2014;

Raajmakers & Shiffrin, 1981).

I reason that testing can both strengthen items’ memory trace (through cue–

target and item-specific processing) and create item-context associations

(through context encoding and reinstatement). Critically, though, the degree

to which context encoding and reinstatement occurs depends on the nature of

the retrieval situation (Karpicke et al., 2014). The more item cues are available

during retrieval or the stronger they are, the lesser the learner needs to capi-

talize on current and previous contextual representation to probe the searched

item information. Thus, testing via cued recall or recognition, similar to en-

actment, may strengthen items’ memory trace and capitalize less on contex-

tual information, leading to the similar and nonadditive effects of both study

techniques in the present thesis. However, testing via free recall should de-

pend to a larger degree on context encoding and reinstatement, in addition to

71

strengthening the item representation. Therefore, the processing overlap be-

tween testing via free recall and motor enactment should be reduced. These

assumptions are consistent with the finding that testing and enactment effects

are both moderated by the type of memory test, but in opposite ways. The

testing effect is more pronounced when less item cues are provided in the re-

trieval situation and more context information needs to be encoded and rein-

stated ( free recall > cued recall > recognition; Karpicke et al., 2014; Kornell

et al., 2011). In contrast, the enactment effect is largest when more item infor-

mation is available and more retrieval relies on the strength or distinctiveness

of the item representation (recognition tests > cued recall > free recall; Kubik,

Obermeyer et al., 2014; Steffens et al., 2009). Future research should investi-

gate how testing and enactment permit the encoding of contextual information

and restrict the search for the target items to a specific temporal context. With

the multiple-list learning paradigm, this possibility can be tested in a straight-

forward manner (Lehman et al., 2014; Szpunar et al., 2008). Participants study

several lists of action phrases; however, later, they should exclusively retrieve

action phrases from the last list, which can be viewed as a particular temporal

context. Crucially, after each studied list, the participants should process all

action phrases once more from the preceding list in one of the four conditions:

(i) testing via free recall, (ii) testing via cued recall, (iii) enactive encoding,

and (iv) receiving only a distractor task (control condition). Performance of

correct recall and intrusions from previous lists should indicate how far these

conditions can use context information to restrict the search set of target items

to a specific list context. I assume that testing via free recall, relative to the

control conditions, should increase correct recall and decrease prior list intru-

sions (Lehman et al., 2014). In contrast, enactment and testing via cued recall

should decrease these performance measures of time-constrained retrieval if

they simply elaborate the item representation but ignore or even hamper the

encoding of context information. If testing via cued recall should additionally

encode and reinstate the critical list-context information—a viable possibility

also in the present studies—testing should also enhance the ability of time-

constrained retrieval, though less so than testing via free recall.

In sum, future research should explore the role of episodic context infor-

mation for the mnemonic effects of testing and enactment. Performing an ac-

tion may enhance remembering its occurrence later on, but not its time and

place. Testing may also enhance memory for the occurrence of events, though

it may additionally encode the current and reinstate the previous episodic con-

texts if the retrieval situation affords it. Such an item-context model for en-

coding (via enactment) and testing effects remains tentative at this point. Fu-

ture research should test specific predictions to elucidate shared and distinct

processes of testing and enactment.

72

Practical Challenges

Beyond the academic endeavor to understand learning principles in experi-

mentally controlled paradigms, translating them into effective educational

practice is an important goal of memory research. Although the present thesis

did not study the practical applications of the findings, they may have impli-

cations for learning in educational contexts and other real-world settings, as

both enactment and testing are effective and readily available tools to enhance

learning and memory.

Action memory research has reliably shown that performed actions are bet-

ter remembered than actions we read about. However, can this memory bene-

fit be generalized to other materials (beyond verb–noun phrases) and to more

educational contexts? Research on memory for gestures may provide an an-

swer. As gestures can be seen as symbolic actions accompanying speech

(McNeill, 1992), they extend the mnemonic effects of actions to less literal

forms of enactment. Similar to our findings regarding the enactment effect,

learning with gestures enhances memory and delays forgetting over longer

delays (Macedonia, 2003). Importantly, these mnemonic benefits generalized

to various learning materials, such as word categories differing in abstractness

(verbs, nouns, and adverbs), foreign language vocabulary, and new words

from an artificial language corpus (for an overview, see Macedonia, 2003;

Macedonia & von Kriegstein, 2012). Moreover, observing a speaker gesturing

led to better memory performance than observing a speaker not gesturing or a

gesturer not speaking (Thompson, 1995; Kelly, Barr, Church, & Lynch,

1999). These findings are in line with the embodied-cognition perspective that

the body can be used as a learning tool in educational contexts to enhance

learning and memory by producing actions that literally (i.e., enactment) or

nonliterally (i.e., gesturing) reflect the content of the information.

Research on the testing effect has obvious implications for education practice.

Often, tests and examinations are still regarded as assessment tools of learning

but not as active tools to enhance learning and memory. Thus, they are kept

to the necessary minimum and occur only cumulatively at the end of the term.

Recent research has provided evidence that the positive testing effect from

laboratory research translates to many situations in which real-world features

of educational contexts are instantiated. For example, with respect to mne-

monic benefits of testing were demonstrated for educationally relevant study

materials (foreign language word pairs: Pyc & Rawson, 2007; idea units from

prose passages: Roediger & Karpicke, 2006b) and educationally relevant re-

trieval formats (quizzes: McDaniel, Agarwal, Huelser, McDermott, & Roedi-

ger, 2011; short-answer test: McDaniel et al., 2007) as well as both in the

laboratory context (Butler & Roediger, 2007) and in less controlled classroom

environments (McDaniel et al., 2007). Further research may evaluate how

testing influences the acquisition of abstract, flexible abilities (such as reason-

ing or flexible and creative thinking), in addition to the learning of facts and

text material, and determine the conditions that moderate the testing effects

73

on learning and retention specifically in educational contexts. For example,

should retrieval practice be spaced out over time, and should curricular con-

tents be blocked within knowledge domains or rather interleaved across them?

To answer these and related questions, retrieval practice and other learning

principles may be “packed” into specific educational instructions and pro-

grams (Pashler et al., 2007). In this way, potential restrictions in implementing

(and combining) effective learning principles into educational practice can be

addressed (e.g., due to the curricular schedule).

74

Concluding Remarks

In the present thesis, I investigated the individual and combined effects of

interleaved testing (via repeated study–test practice) and encoding (via motor

enactment) during learning on later cued-recall performance of action phrases.

An additional objective was to examine the moderating role of recall type

(noun-cued recall of verbs vs. verb-cued recall of nouns) on the direct and

indirect testing effects. The main findings are recapitulated below:

(1) Testing directly enhanced long-term retention of action phrases by re-

ducing the rate of forgetting over 1 week, relative to study-only.

(2) Testing indirectly enhanced subsequent memory performance by fa-

cilitating subsequent re-encoding of previously nonrecalled action

phrases.

(3) Testing by means of noun-cued recall of verbs engendered a larger

indirect testing effect than verb-cued recall of nouns. In contrast, the

type of recall did not moderate the direct testing effect.

(4) Motor enactment of action phrases enhanced subsequent memory per-

formance and reduced the rate of forgetting, relative to verbal encod-

ing of action phrases (i.e., the enactment effect).

(5) When both study techniques were combined, the direct effect of test-

ing (in terms of reduced forgetting) emerged only when the action

phrases were verbally encoded, not when they were enacted. How-

ever, the indirect testing effect for action phrases occurred for both

verbal and enactive encoding.

In conclusion, the present findings imply that testing memory benefits the

later retention of action-phrase material in direct and indirect ways and thus

clearly contributes to learning. In addition, the present findings extend the un-

derstanding of how testing might enhance learning in everyday situations, as

remembering often involves action-relevant information. Testing should be

more systematically implemented in educational practice as an effective learn-

ing tool to enhance the sustainability and transfer of learning. However, it is

important to further examine the factors that might moderate the effectiveness

75

of testing in educational contexts. In this thesis, it was observed that the direct

testing effect, in terms of the rate of forgetting, was restricted to verbal encod-

ing while the indirect testing effect occurred for both encoding types, though

it was increased for noun-cued recall. These findings highlight the need to

implement testing with different retrieval formats, such as free recall and

recognition, and in different schedules (with vs. without restudy opportuni-

ties). Future research may also separate more clearly the specific contributions

of direct and indirect testing effects to better understand their common and

distinct mechanisms.

In addition, the results of the thesis imply that not only testing but also

encoding via enactment is an effective tool to enhance learning and memory.

In fact, when learning was enhanced though enacting, the potential benefits of

testing were limited to the indirect effects. Future research should generalize

this study technique more systematically to other materials apart from action

phrases and in general also to materials for which the contents to be learned

may not necessarily map the performed actions. For example, enactment by

means of gestures has been shown to enhance learning of foreign language

vocabulary and of dialog materials in the context of professional acting (Noice

& Noice, 2001; Noice, Noice, & Kennedy, 2000). In this way, it is possible to

assess the value of enactment—both in literal and nonliteral forms—in learn-

ing materials and environments more relevant from an educational standpoint.

From being a neglected and almost forgotten phenomenon, testing has ad-

vanced to one of the most frequently investigated research topics on memory.

Similarly, the enactment effect—being rather known in the circles of memory

researchers—has lately received a resurgent uptake through the contemporary

research trend on embodied cognition. Despite challenges in translating effec-

tive learning principles from controlled lab research into educational practice,

I believe that both testing and enactment can greatly benefit educational in-

struction and programs in future to enhance learning and memory in various

educational contexts.

76

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