False Memories

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PS114: Research Methods in Psychology

Introduction to Lab Class 1 False Memory

Week 6

Thursday, October 27, 2011

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Memory failure

• An event occurs and you witness it but later you have no (poor or distorted) memory for it– If asked at the time you would describe the event

clearly • An event did NOT occur but later you thought that it

had occurred– If asked at the time you would say the event did

not occur


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Remembering an event

• A description of the event is stored when the event occurs (memory trace)

• When you remember the event you retrieve or access the memory trace

• Details of the event become available• Some details may be lost or confused with other

traces


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False memory• How can you remember an event that did not occur?• Create a memory trace as if the event occurred

– Lead the participant to believe that the event occurred

– Get participant to think about the event• Participant may confuse what was thought with what

was witnessed


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Applications

• False memory has important legal implications:• Bias of witnesses (memory distortion) by interrogation• False memories arising during extensive

psychotherapy


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Roediger & McDermott (1995)

• Highly influential study of false memory• False memories can occur

– in the laboratory– over short time scales– reliably produced by word associations


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Word associations

• to find the associates of a word– give the word as a cue– ask the participant for a response

• the general idea is that when the cue word is read other associated words are activated

• If I say “cat” you might think “dog”


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Roediger & McDermott

• They presented short word lists where all items were associates of a critical word or lure

• Immediate free recall of each list• After a delay, recognition of the words was tested• Recognition test consisted of words presented on the

list (old words)• And words not presented on list (new words)


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Roediger & McDermott’s stimuli

• The 96 words used during the study phase were a subset of words taken from lists of 16 words each.

• Each list had a theme.• During recognition phase, participants were presented with

48 old words and 48 new words• The 48 old words were a selection from the study set, with

equal numbers from each of the lists used.• The 48 new words were either taken from unused lists or

were lures• Lures are words taken from the same lists as words

presented in the study phase, but not previously presented.


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Example

• If CHAIR is the critical lure• List items are associates: table, seat, legs, sofa, • Recognition test consists of:• old words: table, seat, legs, sofa,• new words: dog, station, friend, flower• critical lure: chair


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Recognition test

• Words were shown singly, participants made old-new judgments (is the word old or new).

• If they thought the word was old, they should also make a remember-know judgment.

• A ‘remember’ judgment is given when the participant can mentally relive the experience of seeing the word.

• A ‘know’ judgment is defined as a high confidence that the item occurred in the list, but the participant is unable to re-experience their exposure to the word.


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Results

• Seven times more study words were classified as ‘old’ than new words (memory).

• The proportion of critical lures classified as ‘old’ was equal to the proportion of study words.

• Furthermore, the proportions of critical lures classified as remembered or known were equal to those for study words.

• Participants were unable to distinguish items actually presented from the critical lures.


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Why does false memory occur?

• When the study words are presented, associates activate the critical word

• When you see “seat” you think “chair”• Your memory for the words is based on what words

you thought about while the list was presented• Hence you falsely recognize critical lures related to

study words


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Lab Experiment

• A variation on Roediger and McDermott• Some aspects will be the same• Same stimuli: we will use words from their lists, both

during the study phase and during the recognition phase.

• Same structure: study list; filled retention interval; recognition test


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Lab Experiment

• A variation on Roediger and McDermott• Other aspects will be different• Task: participants will be asked to rate their

confidence that they recognize or do not recognize the word

• The total list of 96 words will be randomly presented, rather than in their individual groups.


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Variables

• Independent variable: (manipulated by experimenter)– Type of word– Three levels: old words, new words, and critical

lures

• Dependent variable: (measure of performance)– Recognition confidence rating


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Randomizing the Study list

• It is conceivable that participants are encouraged to think of a theme for the words that are presented in groups

• This experiment will randomize the entire study list


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Procedure

• Study phase:• 96 words: 12 words each from 8 of R&M’s lists

• Recognition phase:• 40 old words: five of the words previously seen, taken

from each of the 8 study-phase lists• 8 critical lures: the 8 themes of the above lists• 48 new words: 6 words each from 8 of R&M’s lists,

NOT previously presented


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Predictions

If lures are falsely recognized due to their association with the study words, then

• Participants will be confident they recognize the old words, and also confident they do not recognize the new words.

• Critical lures will be recognized the same as old words.

The above two findings would allow us to replicate and support the results of Roediger and McDermott (1995).


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Predictions

But, if lures are falsely recognized due to participants being encouraged to think of themes for the free recall task used by R&M, then randomizing the study list should eliminate the effect and

• Participants will be confident they recognize the old words, and also confident they do not recognize the new words.

• Critical lures will be recognized the same as new words.


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Predictions

Or something in between

• It may be the case that randomizing the study list weakens but does not eliminate the false memory effect.

• What pattern of result do you think might happen in that case?


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Roediger and McDermott

Roediger, H.L., III and McDermott, K.B. (1995). Creating false memories: Remembering words not presented in lists, Journal of Experimental Psychology: Learning, Memory, and Cognition 21, 803-814.

Available from short loan as XD6636, or from PsychArticles online, or from the library’s online resources, or here:

http://psych.wustl.edu/memory/Roddy article PDF‘s\Roediger and McDermott 1995.pdf


http://psych.wustl.edu/memory/Roddy%20article%20PDF's%255CRoediger%20and%20McDermott%201995.pdf

http://psych.wustl.edu/memory/Roddy%20article%20PDF's%255CRoediger%20and%20McDermott%201995.pdf

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On Thursday

Compulsory Data Collection– 2.708

See your personal timetable for your start time(2pm, 3pm or 4pm)


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Next week

• Generalization and sample size• Howitt & Cramer, Ch. 4


False Memories

Documents

Transcript of False Memories