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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 1 Dyslexia and fluency: Parafoveal and foveal influences on rapid automatized naming. Manon W. Jones Bangor University Jane Ashby Central Michigan University Holly P. Branigan University of Edinburgh Authors’ Note Correspondence about the paper can be directed to M.W. Jones, School of Psychology, Adeilad Brigantia, Penrallt Road, Gwynedd LL57 2AS, United Kingdom, email: [email protected] . This research was funded in part by grants from the Economic and Social Research Council (RA-000-23-3533). We would like

Transcript of Dyslexia and fluency: - Edinburgh Research Web viewDyslexia and fluency: ... -values for each...

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 1

Dyslexia and fluency:

Parafoveal and foveal influences on rapid automatized naming.

Manon W. Jones

Bangor University

Jane Ashby

Central Michigan University

Holly P. Branigan

University of Edinburgh

Authors’ Note

Correspondence about the paper can be directed to M.W. Jones, School of Psychology,

Adeilad Brigantia, Penrallt Road, Gwynedd LL57 2AS, United Kingdom, email:

[email protected].

This research was funded in part by grants from the Economic and Social Research

Council (RA-000-23-3533). We would like to thank Chuck Clifton for his support during

several phases of this project and Jeff Kinsey for developing the software used in this

study.

KEYWORDS: Dyslexia; fluency; rapid automatized naming; foveal; parafoveal; linear

mixed effects; eye movements.

Word count: 9052 (Abstract, main text body and references)

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 2

ABSTRACT

Fluent reading requires the ability to coordinate serial processing of multiple

items, an ability known to be impaired in dyslexia. Using a serial naming task that has

been shown to index reading fluency, we investigated which aspects of rapid serial

naming are impaired in dyslexia. In two display change experiments, we recorded eye

movements and voice onsets as adult dyslexic and non-dyslexic readers named letters in

an array that included letter pairs which were orthographically and phonologically

confusable (similar). Confusable information was presented parafoveally (Experiment 1a)

and foveally (Experiment 1b) in the second letter of each confusable pair. Linear mixed

effects analyses showed that orthographic and phonological similarity slowed the

processing of dyslexic readers more than non-dyslexic readers. Orthographic effects

arose when orthographically confusable letters were presented in the parafovea, whereas

phonological effects arose when phonologically confusable letters appeared in the fovea.

We discuss how these findings contribute to our understanding of fluency impairments in

high-functioning, dyslexic adults.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 3

TITLE: Dyslexia and fluency: Parafoveal and foveal influences on rapid automatized

naming

A key characteristic of skilled reading is the ability to read fluently, and slow,

effortful reading is often the only remaining indicator of developmental dyslexia in high-

functioning dyslexic adults, who are reading at the college level (Shaywitz & Shaywitz,

2008). Poor reading fluency in adults and children can be predicted by performance on a

rapid automatized naming task (RAN; Denckla & Rudel, 1976), which involves the serial

naming of letters, digits, objects or colours arranged in a 50 item array. This apparently

simple task is nevertheless problematic for dyslexic readers, who have consistently

slower naming times than unimpaired, non-dyslexic readers (e.g., Denckla & Rudel,

1976; see Wolf & Bowers, 1999, for a review). Thus RAN-type assessments are used to

identify children who are likely to be slow readers.

Researchers have used RAN-type tasks to examine the cognitive processes that

support reading fluency in non-dyslexic readers and impair fluency in dyslexic readers

(e.g., Jones, Branigan, Hatzidaki, & Obregon, 2010; Jones, Obregon, Kelly, & Branigan,

2008; Lervåg & Hulme, 2009; Parilla, Kirby, & McQuarrie, 2004; Powell, Stainthorp,

Stuart, Garwood, & Quinlan, 2007). The present study offers an initial investigation into

how parafoveal and foveal processes operate online during rapid serial naming. We

monitored the eye movements of dyslexic and non-dyslexic adult readers as they

completed a RAN-type task. In order to disentangle the influences of parafoveal and

foveal information in serial naming speed, letter arrays were presented using a display

change paradigm (Rayner, 1975) that controlled whether potentially confusable

information appeared parafoveally or foveally (see Figure 1). As confusable information

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 4

was available exclusively in either parafoveal view or foveal view, this novel approach

allowed an examination of the distinct contributions of each stream of information to

serial naming speed, and potentially to reading fluency. Our data offer initial evidence

that fundamental parafoveal and foveal processes operate differently in dyslexics than in

typical readers.

Rapid serial naming appears to tap a microcosm of the processes underpinning

reading fluency, including: attention, feature detection, the activation of orthographic

representations, the integration of visual and phonological information, and motor

activation leading to articulation (Wolf & Bowers, 1999; Misra, Katzir, Wolf, &

Poldrack, 2004). It is therefore important to examine the various processing requirements

of rapid serial naming in order to discover why dyslexic readers are poor performers, as a

step in understanding basic impairments in reading fluency separated from word and

sentence level influences.

One consistent finding emerging from several studies is that RAN-type tasks are

most effective at discriminating good and poor readers’ performance when the stimuli

(e.g., letters) are presented simultaneously in an array rather than as discrete, individual

letters (e.g., Bowers & Swanson, 1991; Jones, Branigan, & Kelly, 2009). Moreover,

evidence shows that when stimuli are presented simultaneously, naming speeds for

individual stimuli are influenced by information associated with adjacent letters in the

array (Jones et al., 2008). These findings suggest that one key determinant of fluency

may be the way in which the reader manages to process parafoveal and foveal

information in contexts where more than one stimulus is present.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 5

Serial naming and fluency. When we read words aloud we largely concentrate

our cognitive resources on the task of identifying the word we are looking at (the ‘target’

item), which is then articulated. However, even before we have initiated articulation of

the target item, we have moved our eyes to fixate on the next item to be processed. This

is the case in reading (e.g., Laubrock, Engbert, & Kliegl, 2005) and in object naming

(Morgan, van Elswijk, & Meyer, 2008).

It is currently unclear to what extent, and how, processing the ‘next’ item to the

right in a series of words and objects overlaps with the processing of the target item. In

the reading literature, researchers debate whether processing of consecutive words is

serial or parallel (see Engbert, Nuthmann, Richter, & Kliegl, 2005, and Reichle, Rayner,

& Pollatsek, 2003, for reviews). In the language production literature, Meyer and

colleagues have shown in a series of object-naming studies that information from

adjacent objects can influence target item viewing and naming times, suggesting parallel

phonological processing of object names (e.g., Morgan & Meyer, 2005; Morgan, van

Elswijk, & Meyer, 2008; Malpass & Meyer, 2010). In letter naming tasks, when adjacent

items in an array are orthographically or phonologically confusable, this confusability

lengthens fixation time and naming latency for the target item (Jones et al., 2008; see also

Compton, 2003, for further evidence of reading group differences on ‘visual’ and

‘phonological’ versions of RAN). Participant responses are slower when adjacent letters

are similar orthographically (e.g., p vs q) or phonologically (e.g., k vs q). Crucially for

our current purposes, these studies found that dyslexic readers naming times are slowed

significantly more than non-dyslexics when the adjacent items in the array are

orthographically and phonologically confusable. These findings and others (e.g., Powell

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 6

et al., 2007) suggest that dysfluency in RAN reflects a more complex problem than just

retrieval of phonological codes (Wagner, Torgesen, Laughon, Simmons, & Rashotte,

1993).

However, we have yet to resolve how the orthographic and phonological

information in two adjacent items intersect with each other and influence processing and

naming times. Do such effects occur during the initial, parafoveal processing of the

neighbouring item, or during later processing when the neighbouring item is fixated?

Further, are the influences of orthographic and phonological processing dissociable, such

that each exerts an independent influence on fluency but on different aspects of item

processing? Or do orthographic and phonological information influence target item

processing and naming similarly in each case? Answering these questions will help us

ascertain how item processing during serial naming influences reading fluency, and

precisely why serial naming is difficult for dyslexic readers.

We conducted two experiments to examine the extent of processing overlap

between orthographic and phonological processing of two adjacent letter items. The

second item in each pair was manipulated so that it was either confusable or non-

confusable with the first item in the pair in a RAN-type serial naming task. In particular,

we were interested in pinpointing the factors that result in the impaired performance of

dyslexic readers as compared to their non-dyslexic peers. Experiment 1a examined

orthographic and phonological influences in parafoveal processing, in which the second

item was parafoveally confusable with the first item; whereas Experiment 1b examined

orthographic and phonological influences in foveal processing, in which the second item

was foveally confusable with the first item. Foveal and parafoveal vision are defined with

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 7

respect to the focus of attention. Foveal vision extends out approximately 1 degree in

either direction (2 degrees in total) from the centre of vision, and is the only region in the

visual field allowing 100% acuity. Parafoveal vision extends from about 1 degree out

from the center of vision to around 5 degrees, and displays somewhat reduced acuity

(Rayner, 1998).

Foveal processing occurs during fixation, and it plays a crucial role in object

naming and silent reading. Eye movement studies of silent reading initially identified the

importance of foveal processing. For example, readers were much slower to read text in

which the foveal information was unavailable than when it was available (Rayner &

Bertera, 1979). The foveal information available during fixation supports word

recognition and, thereby, affects text comprehension (Rayner, 1998; 2009). Production

studies indicate that foveal processing is essential in naming as well. Speakers rarely

name an item without first fixating it (Griffin & Bock, 2000; Jones et al., 2008; Meyer,

van der Meulen, & Brooks, 2000). Furthermore, single object naming experiments

suggest that word selection and phonological encoding processes operate foveally.

Speakers gaze longer at objects with relatively inaccessible names (e.g., flute), than they

do when producing more accessible object names (e.g., arm) (Griffin & Bock, 2000;

Meyer et al., 1998; Meyer & van den Meulen, 2000). Gaze length also reflects assembly

of phonological codes in fluent speech that involves multiple referents. Speakers gaze for

longer at lower frequency and lower codability items, even when the critical item occurs

in the middle of a description (Griffin, 2001).

While the eyes are fixated on one object or word, viewers automatically begin

parafoveally processing information at the next location they will fixate. Multiple-object

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 8

naming studies demonstrate that participants activate phonological information associated

with an object that they have not yet fixated but that they will name next (Morgan &

Meyer, 2005; Morgan et al., 2008; Malpass & Meyer, 2010). Eye movement data

collected during silent reading indicate that readers extract linguistic information from

parafoveal stimuli within 140 ms during the pre-target fixation (Inhoff, Eiter, & Radach,

2005; Sereno & Rayner, 2000). Readers use coarse-grained parafoveal information, such

as word length, to direct eye movements during reading (e.g., Jones, Kelly, & Corley,

2007; Rayner, 1998). Skilled readers use parafoveal phonological information, such as

initial syllable information, to facilitate word recognition during silent reading (Ashby,

2006; Ashby & Rayner, 2004). Other phonological information, such as the number of

syllables, helps to control where the eyes will fixate next during reading (Fitzsimmons &

Drieghe, 2011; Ashby & Clifton, 2005).

Previous research suggests a relationship between reading skill and parafoveal

processing. Whereas skilled readers benefit from phonologically similar parafoveal

previews (Pollatsek, Lesch, Morris, & Rayner, 1992; Ashby, Treiman, Kessler & Rayner,

2006), poor readers do not show phonological preview benefits during reading (Chace,

Rayner, & Well, 2005). Letter categorisation is also more difficult for dyslexic readers,

compared with non-dyslexics, when the item is flanked by other stimuli, suggesting

parafoveal processing impairment in a lateral masking task (Pernet, Valdois, Celsis, &

Demonet, 2006). Therefore, it may be that dyslexic readers process parafoveal

information differently from non-dyslexic readers. Recent research demonstrates that

compensated dyslexic readers are sensitive to parafoveal information (Jones et al., 2008),

and that it may in fact act as a source of interference in their naming (Jones et al., 2009).

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 9

To further examine the influences of parafoveal and foveal information on serial

naming in dyslexic readers, we conducted two eye movement experiments that presented

40 letters in a RAN-like array. We used these multi-letter displays to pinpoint the specific

processes that contribute to slow serial naming in dyslexic readers, and thus to identify

the possible processes that contribute to reading fluency impairments (or slow reading in

dyslexics). An eye–contingent, display change paradigm (Rayner, 1975) controlled when

the confusable information appeared (parafoveally or foveally). To our knowledge, this is

the first serial naming study to utilize display changes in letter arrays in order to examine

the parafoveal and foveal processes that occur during rapid serial naming. This

methodological development is important for studying a ‘continuous’ naming paradigm,

and it allows the generalization of our results to offline assessments, such as the RAN

(Denckla & Rudel, 1976) or Rapid Letter Naming (Wagner, Torgesen, & Rashotte,

1999), that have established slow serial naming speed as an indicator of reading

difficulties (Schatschneider, Fletcher, Francis, Carlson, & Foorman, 2004; Wimmer &

Mayringer, 2002; Wolf & Bowers, 1999).

Experiment 1a: How does parafoveal information influence serial naming speed?

Experiment 1a examined whether information gained exclusively from parafoveal

vision (i.e., early processing) influences processing times and/or the onset of articulation

times in a RAN task. We compared the performance of age-matched, high-functioning

adult groups of non-dyslexic and dyslexic readers on a RAN-letters task that manipulated

parafoveal information. Specifically, we manipulated whether the parafoveal information

available to readers in position n+1 was orthographically or phonologically confusable

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with the information presented in position n, and measured whether confusability affected

participants’ eye movements compared to conditions in which the parafoveal information

was neither orthographically nor phonologically confusable.

The design of this experiment was in many respects similar to the design of Jones

et al. (2008): Letters were presented in an array of four lines containing ten items each,

and confusability was manipulated by varying the orthographic similarity of adjacent

pairs of letter shapes (e.g., p-q; b-d) and the phonological similarity of the onset in the

letter names (e.g., q-k; g-j). However, unlike in Jones et al. (2008), we used a contingent

change paradigm, so that confusable information was presented only parafoveally: When

the participant actually fixated the location where the confusable information had

appeared, the confusable letter was replaced by a non-confusable letter. For example, in

the orthographically confusable condition, when a participant fixated the target item q (in

position n), the orthographically confusable letter p was viewed in the parafovea (in

position n+1). When the eyes saccaded across an invisible boundary to the immediate

right of the target item in position n, the confusable letter p (or non-confusable letter k) in

position n+1 was replaced by a non-confusable target item, such as f (see Figure 1).

[INSERT FIGURE 1 ABOUT HERE]

To study the effects of parafoveal confusability, we used two measures. As in

Jones et al. (2008), the processing time measure is the sum of all fixations on a letter

before the eye saccades away from it. This measure, which is also known as first-pass

duration, is thought to include processing stages from visual information uptake to

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 11

activation of phonological codes (Griffin, 2001, 2004). Our second measure was eye-

voice span, or time from the onset of the first fixation on a letter to the onset of the

articulatory response for that letter. This measure, also known as naming latency,

includes the time taken to identify the letter and to complete the phonological assembly

and articulatory planning of its name. Thus, the eye-voice span measure reflects

processing time plus additional processing stages up to the point of articulation of the

correct item. Previous research indicates that the eye looks at least one object ahead of

the verbalized object (Griffin, 2004; Laubrock et al., 2008). In our previous serial naming

study, eye-voice spans were at least 200 ms longer on average than the processing time

measure (Jones et al., 2008). Thus, eye-voice span incorporates relatively later processes

that are specific to speech production (Levelt, Roelofs, & Meyer, 1999).

In skilled reading, it is well established that orthographic and phonological

information are initially processed parafoveally (Pollatsek & Rayner, 1992; see Rayner,

Pollatsek, Ashby, & Clifton, 2012 for a review of this literature). We examined whether

parafoveal processing contributed to the effects observed in Jones et al. (2008).

Therefore, we predicted that non-dyslexic readers would yield longer processing times in

response to confusable compared with non-confusable items. For dyslexic readers, we

predicted longer eye-voice spans in response to confusable compared with non-

confusable items (and compared with non-dyslexics’ eye-voice spans to these items). The

precise pattern of effects would also be informative about the nature of parafoveal

confusability, and specifically whether such effects are associated with orthographic

confusability, phonological confusability, or both.

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Group differences in processing speeds and eye-voice spans were measured on

item n (NEXT confusability, in which latency on the first item in the pair is measured)

and on item n+1 (PREV confusability, in which latency on the second item in each pair is

measured). As Jones et al. (2008) found that confusability effects extended in both

directions (i.e., both groups showed an effect when a confusable item appeared before a

target item and when it appeared after a target item), we expected to find confusability

effects in the PREV and NEXT analyses for both groups of readers.

Method

Participants. Two groups of 16 native English-speaking students participated in

this study. The dyslexic-reader group comprised students with a formal diagnosis of

dyslexia (10 females; 6 males). They were assessed during primary or secondary

education (before the age of 16) by an educational psychologist. This assessment was

confirmed during their university career. The non-dyslexic-reader group comprised

students who reported no difficulties with speech or literacy (11 females; 5 males). The

groups did not differ in age (Dyslexic-reader group: mean = 21 years, SD = 1.99; Non-

dyslexic-reader group: mean = 21 years, SD = 1.42).

Design & stimuli. Both groups were tested on a battery of cognitive and literacy

measures. These tests were administered in order to ensure that these high-functioning

dyslexic readers were poorer than non-dyslexics on literacy-related tests, whilst obtaining

comparable results on IQ measures (Snowling, 2000). Tests included rapid (letter)

naming (Comprehensive Test Of Phonological Processing [CTOPP]; Wagner et al.,

1999), word recognition (Wide Range Achievement Test [WRAT-3]; Wilkinson, 1993),

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 13

digit recall, assessing short-term and working memory (Miles, 1993). A spoonerism task

assessed phonological awareness (Hatcher, Snowling, & Griffiths, 2002). We also tested

participants on verbal (Vocabulary) and non-verbal (Block design) sections of the

Wechsler Adult Intelligence Scale – 3rd edition (WAIS-III; Wechsler, 1992). The

cognitive and literacy tests took approximately 25 minutes to administer.

We created 16 experimental trials, each comprising a 10 x 4 array of letters. Of

the 40 items in each array, 8 items (2 in each row) were subject to a gaze-contingent

display-change (Rayner, 1975). We manipulated the phonological and orthographic

confusability (confusable vs. non-confusable) of parafoveal letters with respect to the

preceding letter in the array. Four trials in the experiment comprised orthographically

confusable items, in which letters were mirror images of one another on the vertical axis:

(p – q; b – d) and another four trials comprised phonological (onset) confusable items (g

– j (onset /dЗ/); k – q (onset /k/). Critical items were presented in positions n and n+1.

Four non-confusable equivalent trials were presented for both the phonological and

orthographic conditions (Orthographic: (P – Q; B – D; Phonological: g – k; j – q).1 Thus,

the same items appeared in phonologically non-confusable trials as in confusable trials;

the only difference was that confusable items appeared adjacent in confusable trials (e.g.,

g-j), but non-adjacent in non-confusable trials (e.g., g-k).

Note that orthographically non-confusable trials involved exactly the same

phonological output as the orthographically confusable trials: The same letters appeared

in the same order across conditions, differing only in letter case (e.g., orthographically

non-confusable: P-Q; orthographically confusable: p-q). In order to exclude any

explanation of a confusability effect in the orthographic condition based on letter case,

1 See footnote 1.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 14

letters in the phonological sets were also upper case on half of the trials (between-

participants). Our design yielded a possible 32 data points per cell.

The gaze-contingent display-change meant that confusable information in position

n+1 could be viewed only in the parafovea (whilst the participant was fixating the letter

in position n). For example, if the participant fixated on the letter q as the first member of

a target pair, it was possible for them to view the confusable item p parafoveally until the

eye crossed the invisible boundary line between positions n and n+1. Crossing the

boundary triggered a display change, such that the item in position n+1 changed to an

item that was not confusable with the first member of the pair. In all trials, letters in

position n+1 that had previously been confusable with letter item n changed into non-

confusable letter items: f or l. Filler items included the letter z and the letters f and l were

presented (at least once in each trial) to avoid the sequence becoming too predictable.

Four between-subjects lists were created in order that the order of confusable pairs could

be counterbalanced (e.g., p – q and q – p) in addition to the position of target items within

the 4 x 10 letter arrays.

The experiment yielded a 2 (dyslexic vs. non-dyslexic) x 2 (confusable vs. non-

confusable) design for the phonological-onset letter pairs and for the orthographic letter

pairs. Analyses were conducted for processing time and eye-voice span measures,

resulting in four analyses in total.

Apparatus. Eye movements were monitored by an SR Research Eyelink 1000

eyetracker. Fixation position was sampled at 1000Hz and saccades prior to critical

fixations were detected using a 17-sample saccade detection model with a velocity

threshold of 30 °/sec, an acceleration threshold of 8000 °/sec2, and a minimum amplitude

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 15

of 0.5°. Viewing was binocular, but only the right eye was tracked. The letter arrays were

presented using custom designed software (Eyetrack 0.7.10k) on a 21 inch Iiyama

HM204DTA CRT monitor at a viewing distance of 60 cm. Each 10 x 4 array was

presented as white text on a black background. Each letter was presented in 18 point font

(1:6 spacing) and subtended a visual angle of 0.5° x 0.5° (the region of interest allocated

for each item comprised 76 pixels horizontally). Lines in the array were triple-spaced.

The gaze-contingent boundary was placed immediately to the right of a letter item in

position n, with a visual angle of 3° between the boundary line and the letter item in

position n+1. The centre-to-centre distance between each item was 3.5°. The position of

gaze-contingent pairs in a line varied within and across trials. The monitor displayed text

at a 150-Hz refresh rate that permitted display changes within 6 ms. The display change

completed during the saccade, and participants rarely noticed any change other than a

screen flicker. Participants’ spoken output was recorded on the PC via a Direct X sound

card; recording began automatically at the beginning of the trial and terminated at the end

of the trial. Speech onsets were subsequently obtained using professional sound editing

software (a script was used to record onsets when the sound wave reached a specified

intensity).

Procedure. The experiment began with adjustment of the infrared cameras

attached to the eyetracker, followed by a brief calibration procedure in which participants

viewed dots in 9 screen locations. Calibration was checked before each trial and the

recalibration procedure was repeated as necessary between trials to maintain accuracy.

Each trial in the experiment began with a drift correction (comprising a small square) in

the same position as the first object to be named (top left hand corner of the screen).

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 16

When the participant’s eye fixated the square, it automatically triggered presentation of

the next trial in the experiment. Participants were instructed to name each item, starting

from the top left hand object and moving as quickly as possible in a left-to-right and

down fashion until they got to the final item, whereupon they were instructed to terminate

the trial with a button press. The experiment was self-paced. A total of 32 trials (10 x 4

grids) were presented in one experimental session (16 trials from the parafoveal

experiment described here were interspersed with 16 trials from the foveal experiment;

see Experiment 1b below). Trial presentation was randomized and a session lasted

approximately 30 minutes.

Results and Discussion

Cognitive and literacy tests Dyslexic readers showed significantly poorer

performance on the RAN measures and the single word reading measure than did the

non-dyslexic readers. Significant group differences were also found on memory tasks

(Forward and Backward digit span). Critically, the dyslexic group did not show a

significant difference on measures of global intelligence (WAIS Vocabulary and Block

design). Group differences did not reach significance on the phonological awareness

measure (Spoonerisms). Each member of the dyslexic group obtained a RAN score

(composite of Letters and Digits) that was at least 1.5 SD below the non-dyslexic mean

RAN score. None of the dyslexic readers in this study were therefore excluded from the

main analyses. Table 1 shows group difference scores on each test.

[INSERT TABLE 1 ABOUT HERE]

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 17

Eye-movement parameters, speech onsets & analyses. The eye-movement

parameters used in this experiment were similar to those used in Jones et al. (2008).

Using the region of interest allocated to each item, we could determine when, with

reference to a zero point representing the beginning of the trial, the participants’ gaze

entered each region and how long the participant stayed in each region before saccading

to the next region.

Correct speech responses were matched to the relevant eye fixation data in order

to calculate eye-voice spans for each item (speech responses were measured relative to

the same zero point as the eye-fixation data). Approximately 17% of the data was

excluded owing to track losses. This figure is commensurate with recent reports of track

losses in the contingent change literature (e.g., White, Rayner, & Liversedge, 2005).

Two measures were calculated: First, processing time (first pass reading time;

Rayner, 1998) measured the time spent fixating each item before the eye saccaded to the

next item. Second, the eye-voice span measured the time between the onset of the first

fixation on a letter to the onset of articulation of the letter name. The processing time and

eye-voice span measures included only correctly named letters that were preceded or

succeeded by a related or unrelated item.

Linear Mixed Effects (LME) models were used to analyse the data (see Baayen,

2008; Baayen, Davidson, & Bates, 2008), implemented with lme4 (Bates, Maechler, &

Dai, 2008), and languageR packages (Baayen, 2008) in R (R Development Core Team,

2008). LME models enable separation of the experimental manipulation(s) under

observation (fixed effects) from spurious or ‘random’ effects, which is a particularly

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 18

useful method for analyzing data from heterogeneous groups (such as groups with

dyslexia) performing a complex task such as RAN (see Jones et al., 2008 for a detailed

account of the advantages of using LME for this type of research). Analyses (processing

time / eye-voice span) included two fixed effects: 1) Confusability (non-confusable vs.

confusable); and 2) Group (non-dyslexic vs. dyslexic). Non-dyslexic/non-confusable

conditions comprised the intercept (baseline condition) in each analysis, against which

other conditions were compared. A significant fixed effect of ‘confusability’ occurred if

the non-dyslexic/confusable condition contributed unique variance to the model beyond

the baseline condition. A significant fixed effect of ‘group’ occurred if the dyslexic/non-

confusable condition contributed unique variance to the model beyond the baseline

condition. Finally, an interaction occurred if the dyslexic/confusable condition

contributed unique variance to the model beyond that explained by the additive

contribution of the other conditions (non-dyslexic/ non-confusable + non-dyslexic/

confusable + dyslexic / non-confusable); in other words, an interaction indicated a greater

effect of confusability in the dyslexic group than would be expected on the basis of a) the

non-dyslexic group’s performance in the confusable condition and b) the dyslexic

group’s own performance in the non-confusable condition (also see Table 2 note).

For each dependent measure (i.e., processing time and eye-voice span), separate

analyses were conducted for NEXT-confusable and PREV-confusable effects (see Figure

1): ‘NEXT-confusable’ analyses considered response times to the first item (n) when the

next item in the array (n+1), was parafoveally confusable, relative to conditions when it

was not confusable. We assume that attention shifts to item n+1 when available,

presumably during a late phase of processing item n (Reichle et al., 2003). As in previous

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 19

work, we associate NEXT-confusable effects with initial processing of item n+1

intersecting with processing of item n. In contrast, ‘PREV-confusable’ analyses

considered response times to item n+1 (when the previous item in the array, in position n,

was parafoveally confusable with the letter that appeared in position n+1, i.e., before it

was fixated, relative to conditions when it was not confusable). In earlier work we

associated PREV-confusable effects with the lingering effects of processing item n on

processing item n+1 (Jones et al., 2008).

Participant, item, character (letter), and other item variances were entered as

random effects measures. Since our task is essentially an uninterrupted stream of serial

item naming, every target item had both following and preceding neighbours that we

expected to influence the processing of the target item. For the other item random effect

variable we, therefore, grouped the target with the item on the other side. If our analysis

examined the effect of a preceding item on the target item, for example, we assigned the

effect of the succeeding item on the target item to the random effect variable other item.

Thus, we could measure the effect of the previous item on the target independently of any

additional influence from the item succeeding the target item.

For each analysis we report t-values for each coefficient and estimated

probabilities based on 10,000 Markov chain Monte Carlo (MCMC) samples. MCMCs are

recommended because of the difficulty in determining degrees of freedom corresponding

to each t-value for the model coefficients.

Processing time and eye-voice measures were positively skewed, and therefore

logged in order to normalize the distribution. The results of all analyses are presented in

Table 2. For the sake of clarity, we only discuss and graphically represent findings that

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 20

were statistically significant in terms of confusability effects for non-dyslexic and

dyslexic groups (as these are the effects of crucial interest in this paper). However, we

note here that in most analyses, dyslexic readers were slower on both processing time and

eye-voice span measures (irrespective of the confusability manipulation), which is

consistent with previous findings (Jones et al., 2008).

[INSERT TABLE 2 HERE]

For the processing time measure, analyses of the orthographic conditions yielded

an interaction model best fit for the PREV-confusable analysis only (χ² (1) = 4.27, p

< .05; see Figure 2): Dyslexic readers were significantly slower to process a target item

(in position n+1) if it had been orthographically confusable when viewed in the

parafovea (t = 2.13, p < .05), than would be expected on the basis of a) dyslexic readers’

own performance on non-confusable items; and b) non-dyslexics’ performance on both

non-confusable and confusable items. All other processing time and eye-voice indicated

no significant differences in confusability effects between participant groups. Standard

deviations of the random effects variables in all reported analyses (additive / interaction

models) are presented in table format in Appendix A.

[INSERT FIGURE 2 ABOUT HERE]

Results from Experiment 1a indicate that the orthographic confusability of

parafoveal information slowed the processing times of dyslexic readers compared with

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 21

non-dyslexic readers. Specifically, dyslexics had difficulty in inhibiting confusable

information from the previous item (n) in the array when they parafoveally processed the

following confusable item (n+1), even though the confusable information was no longer

present when item n+1 was fixated. In contrast, non-dyslexic readers’ mean processing

times were reduced by the presence of orthographically confusable information in the

parafovea (but note that the fixed effect comparison for orthographically confusable

versus non-confusable information for non-dyslexics was not significant). The present

data did not indicate any effects of orthographic confusability on eye-voice span.

Experiment 1b: How does foveal information influence serial naming speed?

Experiment 1b investigated the role of foveal information in rapid serial naming

by manipulating the foveal confusability between neighbouring items in the array. Here

the second item in a target pair was non-confusable when viewed in the parafovea but

became confusable with the first item in the pair when it was fixated. Items viewed in the

fovea are subject to more in-depth processing than items viewed in the parafovea (Rayner

& Pollatsek, 1989; Rayner et al., 2012). In this experiment, critical items were fully

processed in terms of retrieval of phonological codes and phonological assembly for

articulation (because the confusable item’s name was articulated); this was in contrast to

Experiment 1a, where confusable items in position n+1 need not be fully encoded for

articulation (because the confusable preview item name was not articulated).

Experiment 1b therefore investigated whether information gained exclusively

from foveal vision (i.e., during fixation) influences processing times and/or eye-voice

spans in a RAN-type task. As in Experiment 1a, we studied the effects of orthographic

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 22

and phonological confusability in non-dyslexic readers, but our critical interest concerned

how confusability affected dyslexic readers. The same groups of age-matched, high-

functioning non-dyslexic and dyslexic readers performed a RAN-letters task that was

almost identical to Experiment 1a, except that the confusable item was presented

foveally. For example, when a participant fixated the letter q, a non-confusable item (e.g.,

f) was visible in the parafovea (in position n+1). When the eye saccaded across an

invisible boundary to the immediate right of the first item, the letter in position n+1 was

replaced by a letter that was confusable relative to the first item in the pair, such as p (see

Figure 3). Thus, the second item in the pair was not confusable when viewed in the

parafovea, but became confusable when fixated.

[INSERT FIGURE 3 ABOUT HERE]

NEXT-confusable analyses indicated an influence of foveal information from the

second item (n+1) on the complete phonological assembly of the first item (n). The

NEXT-confusable analysis could only yield meaningful results in the eye-voice span

measure, in which the eye’s lead ahead of the voice would have triggered the confusable

change in the second item before production processes completed on the first item. In

contrast, processing time on the first item would not register the effect of confusability in

the second item, as the eye would not have yet triggered display change that revealed its

confusability. PREV-confusable analyses indicated the influence of the first letter (n) in

the pair on the processing of the following item (n+1). Item n+1 became confusable with

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 23

item n only upon fixation, in order that we could examine whether processing of item

n+1 was influenced by foveal processing of item n.

Experiment 1b examined whether foveal processing contributed to the

confusability effects found in earlier work on RAN performance (Jones et al., 2008), and

whether its contribution to naming is qualitatively different from that of parafoveal

processing (Experiment 1a). Our hypotheses for this experiment followed the same logic

as the hypotheses for Experiment 1a; we examined whether foveal processing contributed

to the effects observed in Jones et al. (2008). Therefore, we predicted that non-dyslexic

readers would yield longer processing times in response to confusable compared with

non-confusable items. For the dyslexic readers, we predicted longer eye-voice spans in

response to confusable compared with non-confusable items (and compared with non-

dyslexics’ eye-voice spans to these items). The precise pattern of effects would also be

informative about the nature of foveal confusability, and specifically whether such effects

are associated with orthographic confusability, phonological confusability, or both.

As Jones et al. (2008) found that confusability effects extended in both directions

(i.e., both groups showed an effect when a confusable item appeared before a target item

and when it appeared after a target item), we expected to find confusability effects in the

PREV and NEXT analyses of eye-voice span for both groups of readers. Such a finding

in the NEXT analyses would suggest that the time taken to initiate articulation of the first

item is influenced by processing features of the second item. We also expected significant

effects of confusability in the PREV-confusable analyses. This would suggest that

inhibiting confusable information from the first item is difficult and prolongs processing

of the item in the second position.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 24

Method

Participants. Participants who took part in Experiment 1a also took part in

Experiment 1b.

Design and stimuli. The design of Experiment 1b was identical to Experiment 1a

except for one crucial difference: In Experiment 1b, confusable information was visible

only in the fovea, as described above.

Procedure. The procedure of Experiment 1b was identical to Experiment 1a.

Results and Discussion

Processing time and eye-voice measures were logged in order to normalize the

distribution. The results of all analyses are presented in Table 3. As in Experiment 1a, we

only discuss and graphically represent results that were statistically significant in terms of

confusability effects for non-dyslexic and dyslexic groups. Standard deviations of the

random effects variables in all reported analyses (additive / interaction models) are

presented in table format in Appendix A.

[INSERT TABLE 3 HERE]

Processing time. The interaction model provided a marginally better fit in the

orthographic PREV-confusable analysis (χ² (1) = 3.00, p = .08) (see Figure 4). Non-

dyslexic readers looked longer at the second item when it was orthographically

confusable with the first item in the pair than when it was not (PREV-confusable: t =

2.80; p < .05). In contrast, dyslexic readers showed similar processing times for the

second item, irrespective of its orthographic confusability, (t = 1.96, p < .05).

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 25

[INSERT FIGURE 4 ABOUT HERE]

Eye-voice span. A significant Group x Confusability interaction occurred in the

eye-voice span measures in the phonological-confusability conditions (PREV-confusable:

χ² (1) = 6.56, p < .01; NEXT-confusable: χ² (1) = 4.00, p < .05) (see Figure 5). Dyslexic

readers’ eye-voice spans were longer than would be expected compared with a) their

performance on non-confusable items; and b) non-dyslexics’ performance on both non-

confusable and confusable items. This occurred in both NEXT-confusable (t = 2.01; p

< .05) analyses and PREV-confusable (t = 2.56; p < .05) analyses.

Results from Experiment 1b showed that whilst non-dyslexic readers’ processing

times were slowed as a function of foveal orthographic confusability, dyslexic readers

were relatively insensitive to the orthographic confusability manipulation. However,

dyslexic readers were significantly slower to initiate an articulatory response to the first

item in a target pair when the second item was phonologically confusable and, similarly,

were slower to name the second item when the first item was confusable. Thus,

phonological similarity in the names of the two fixated items impaired processes

associated with assembly of phonological codes in preparation for articulation (eye-voice

span).

[INSERT FIGURE 5 ABOUT HERE]

General Discussion

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 26

One key characteristic of rapid naming is that it involves rapidly processing a

series of items. When naming a series of items, we process the fixated, foveal item and

some aspects of the upcoming, parafoveal item to its right (Morgan & Meyer, 2005). The

present study examined how parafoveal and foveal information contributes to rapid serial

naming speed, which is generally considered to index reading fluency (Schatschneider et

al., 2004; Wimmer & Mayringer, 2002; Wolf & Bowers, 1999). In order to examine how

orthographic and phonological information influenced rapid naming in normal and

dyslexic readers, we manipulated the orthographic or phonological confusability of

adjacent items online as participants named letters displayed in an array. Experiment 1a

investigated the effect of manipulating the confusability of n+1 when it appeared in

parafoveal view. Experiment 1b investigated the effect of manipulating the confusability

of n+1 when it appeared in foveal view. Data from these experiments provide clear

evidence that orthographic and phonological information obtained from parafoveal and

foveal sources affected eye-movements and eye-voice spans during serial naming.

Moreover, the nature and source of these confusability effects differed between reading

groups.

Non-dyslexic readers. Our typical readers did not exhibit orthographic or

phonological confusability effects for letters that were only confusable when in

parafoveal view (Experiment 1a). This could suggest that the non-dyslexics were able to

minimize any detrimental impact of parafoveal information, at least in this non-reading

context. This is consistent with previous research indicating that typical readers used

parafoveal information mainly to facilitate the identification of n+1 (Rayner, 2009).

The non-dyslexic readers were slower to process foveally confusable items when

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 27

the target was orthographically similar to the previous item in the array than when it was

not (Experiment 1b). This finding suggests that during rapid serial naming in normal,

skilled readers, foveal processing of a stimulus can be influenced by the orthographic

features of the previous item (i.e., orthographic spillover effects). Studies of text reading

show that shared orthographic neighbourhoods increase target viewing times, an effect

particularly visible in later processing measures (total time and regressions) and which

has been attributed to lateral inhibition at the lexical level (e.g., Acha & Perea, 2008).

Our task required lexical retrieval of letter names, rather than words, but we propose a

similar explanation: Strong activation of an orthographic form immediately prior to the

target in this experiment inhibited activation of an orthographically similar

representation. Non-dyslexics’ sensitivity to orthographically confusable information that

appeared during a fixation is consistent with previous evidence of longer processing

times in response to adjacent orthographically confusable items (Jones et al., 2008). Non-

dyslexic readers were not, however, sensitive to phonological confusability in either

experiment.

Dyslexic readers. When dyslexics were presented with orthographically

confusable items (Experiment1a), parafoveal confusablility of the second letter resulted

in slower processing times on average when the second item was fixated. This finding

suggests that during rapid serial naming, dyslexics' processing of two consecutive letters

can be disrupted by parafoveal information from the second letter, compared with non-

dyslexics. This finding is consistent with previous evidence of dyslexic parafoveal

processing impairment in a lateral masking task (Pernet et al., 2006). Interestingly,

parafoveal orthographic confusability slowed processing times for the second item in the

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 28

pair rather than for the first item, even though the second item was not confusable when

fixated. This suggests a lag in the interference from parafoveal information, which could

be attributed to slower parafoveal processing in dyslexics. Therefore, the dyslexic data

from Experiment 1a raises the possibility that sluggish parafoveal processing may

contribute to dyslexic readers’ problems with reading fluency. When the same

orthographically confusable information was only available foveally (in Experiment 1b),

dyslexic readers were not sensitive to orthographic confusability effects (although non-

dyslexic readers were).

In contrast, phonologically confusable information presented in foveal view

lengthened the eye-voice spans of dyslexic readers in Experiment 1b. This is consistent

with previous research suggesting problems with dyslexics’ retrieval of phonological

codes for production (Clarke et al., 2005; Jones et al., 2008; Wagner et al., 1993). Also,

these data indicate that foveal phonological confusability slows dyslexic readers’ naming

latencies in two situations: both in naming the target item whilst the eye has moved on to

the next, phonologically confusable item (i.e., activation of to-be-named phonological

codes disrupt phonological assembly on the target item), and in naming the target item

when the previous item in the array was phonologically confusable (i.e., failure to

disengage from already articulated phonological codes disrupts phonological assembly on

the target item).

Taken together, our results suggest that dyslexic readers experience a processing

bottleneck, in which they tend to experience greater difficulty than non-dyslexic readers

in selecting one representation from competing alternatives (e.g., that the letter q is a q as

opposed to a visually similar letter such as p, or a letter with a phonologically similar

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 29

name such as k). Thus, during the early (parafoveal) stages of processing, dyslexic

readers are slower than non-dyslexic readers to activate one orthographic code among

several alternatives (or to distinguish between two very similar orthographic codes). At

later (foveal) stages of processing, when required to commit to a phonological code for

articulation, dyslexic readers have more difficulty selecting the appropriate phonological

code from competing alternatives. It seems likely that the confusability effects observed

in dyslexic readers stem from degraded orthographic and phonological representations,

which are more difficult to distinguish and therefore slower to select and retrieve (see

Perfetti, 2007). Our findings may reflect separate orthographic and phonological deficits,

each exerting independent influences and resulting in separate impairments (see Rayner

et al., 2012 for further discussion). Alternatively, it is possible that a single mechanism is

responsible for degraded representations in both domains.

This study extends our understanding of why dyslexic readers perform more

slowly on serial naming tasks than skilled readers. Jones et al. (2008) initially established

that the presence of orthographically confusable and phonologically confusable

information in adjacent letters increased letter naming latency in dyslexic readers,

however that study was not designed to discriminate parafoveal from foveal sources of

the confusability effects. The effects found in the present study are consistent with

findings from Jones et al. (2008), however the confusability effects found here were not

as pervasive as one might expect from previous research. For example, our dyslexic

readers did not yield longer eye-voice spans in response to orthographic as well as

phonological confusability, and our non-dyslexic readers did not show some of the

confusability effects reported in Jones et al. (2008). The more pervasive confusability

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 30

effects in the previous experiment could be accounted for by differences in how each

study presented parafoveal and foveal information. The present study made confusable

information available either parafoveally or foveally; but the confusable information was

constantly available in Jones et al. (2008). Thus, finding more pervasive confusability

effects in our previous study may reflect the cumulative effect of processing the second

confusable item both parafoveally and foveally.

Implications. By independently manipulating whether the confusable information

was available parafoveally or foveally, the present study allowed us to examine closely

how the processing of orthographic and phonological information intersect across

successive items in a serial naming task. Our data identify two sources of the diagnostic

power of rapid serial naming tests to identify and predict dyslexia. First, dyslexic readers’

viewing times are slowed by confusable adjacent orthographic information in the

parafovea. Second, dyslexic readers’ naming latencies are delayed when confusable

phonological information is available in foveal view.

In summary, this study examined how foveal and parafoveal information

influences serial naming and impairs dyslexic readers’ naming speeds by manipulating

orthographic and phonological confusability. The findings suggest that dyslexics’

processing of orthographic and phonological information differs from non-dyslexics. The

dyslexic readers had difficulty distinguishing between multiple, activated orthographic

codes that appeared only in parafoveal view. They also had difficulty distinguishing

between multiple activated phonological codes that were foveally confusable during the

later, production stages of processing adjacent items.

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Footnotes

1. Note that the items b-d are potentially confusable at the rime level as well as

the orthographic level. In a previous study, however, using identical letter pairs, we

showed that the rime confusability inherent in b-d does not contribute significant variance

naming speed. Furthermore, rime confusability in general does not appear to influence

RAN speeds: a specific rime confusability manipulation did not show any significant

effects in either dyslexic or non-dyslexic groups across several analyses (Jones et al.,

2008). On the basis of these results, we can therefore rule out an influence of rime.

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Table 1. Reading group scores on cognitive and literacy tests.

Dyslexic(16)

Non-dyslexic(16)

t Cohen’s d

Rapid letter naming

MeanSD

17.204.26

11.561.42

5.51*** 1.77

Rapid digit naming

MeanSD

17.204.67

11.051.23

5.08*** 1.80

Word reading MeanSD

46.318.07

53.871.62

3.67* 1.29

Spoonerisms MeanSD

21.259.22

23.001.74

0.74 0.26

Forward digit span

MeanSD

8.682.18

10.371.74

2.41* 0.85

Backward digit span

MeanSD

3.372.02

5.450.96

3.67** 1.31

WAIS – vocabulary

MeanSD

12.752.23

12.751.29

0.00 0.00

WAIS – block design

MeanSD

14.182.80

15.002.39

0.88 0.31

Note. RAN Letters and Digits = RTs (s); Word reading = correct /56, Spoonerisms =

correct /24; Verbal memory = correct: Forward digit span = /12; Backward digit span = /6

points. WAIS = scale scores. *** p < .001; ** p < .01; * p <.05.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 41

Table 2: Experiment 1a: Parafoveal confusability

Fixed Effect Phonological Orthographic

Processing time Eye-voice Processing time Eye-voice

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

Non-dyslexic/Non-confusable (1) baseline

Mean (SE)

460(420-501)

363(322-408)

736(675-803)

699(629-776)

489(437-543)

363(321-408)

745(680-814)

699(631-775)

Non-dyslexic/Confusable (2)

Mean (SE)t

469(443-496)0.67

382(353-416)1.49

725(678-779)0.47

697(658-740)0.09

466(434-502)1.45

385(355-416)1.73

734(690-782)0.52

705(665-750)0.31

Dyslexic/Non-confusable (3)

Mean (SE)t

565(499-637)3.05 **

464(403-535)3.27

817(737-910)1.86 *

837(752-935)3.09 **

544(474-628)1.36

459(392-529)2.82 **

838(751-941)1.92 *

839(760-939)3.17 **

Dyslexic/ Confusable (4)

Mean (SE)t

573(531-619)0.14

476(435-523)0.61

800(742-860)0.19

845(784-907)0.33

566(523-612)2.13 *

486(445-532)0.05

864(804- 925)1.27

881(823-945)1.13

Note. Fixed effects comparisons are made with reference to the baseline condition (non-

dyslexic/ non-confusable condition). A fixed effect of confusability involves comparison

of conditions (1) and (2); a fixed effect of group involves comparison of conditions (1)

and (3); an interaction involves comparison of the additive fixed effect factors: (1) + (2) +

(3) with condition (4). Mean and SE values = ms; * p < .05, ** p < .01.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 42

Table 3: Experiment 1b: Foveal confusability

Fixed Effect Phonological Orthographic

Processing time Eye-voice Processing time Eye-voice

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

Non-dyslexic/Non-confusable (1) baseline

Mean (SE)

478(435-531)

380(336-430)

804(729-887)

733(651-834)

452(411-497)

376(336-419)

758(691-824)

678(602-760)

Non-dyslexic/Confusable (2)

Mean (SE)t

483(446-518)0.31

382(349-419)0.13

829(769-897)0.85

737(668-819)0.12

490(459-522)2.80 *

357(328-389)1.34

782(727-837)0.99

689(642-739)0.56

Dyslexic/Non-confusable (3)

Mean (SE)t

603(528-685)3.19 **

472(411-543)2.85 **

887(785-999)1.51

840(750-939)2.31 *

582(513-658)3.70 **

443(385-503)2.34 **

893(807-995)2.86 **

828(740-934)3.15 **

Dyslexic/ Confusable (4)

Mean (SE)t

579(531-628)1.18

481(437-529)0.27

1017(935-1102)2.56 *

925(844-1009)2.0 *

582(538-631)1.96 *

457(415-501)1.74

920(856-986)0.05

815(749-882)0.8

Note. Fixed effects comparisons are made with reference to the baseline condition (non-

dyslexic/ non-confusable condition). A fixed effect of confusability involves comparison

of conditions (1) and (2); a fixed effect of group involves comparison of conditions (1)

and (3); an interaction involves comparison of the additive fixed effect factors: (1) + (2) +

(3) with condition (4). Mean and SE values = ms; * p < .05, ** p < .01.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 43

Figure 1. Parafoveal confusability manipulation experiment: Illustrative example of

NEXT and PREV analyses (orthographic-confusable and non-confusable conditions).

Note. The symbol denotes the eye position (pre- and post- display change) in

addition to the letter (n or n+1) measured (processing times and eye-voice spans). NEXT

analyses indicate the influence of parafoveal information from the next item (n+1),

affecting processing of item n late in its identification. PREV analyses indicate the

influence of n on the processing of n+1 (i.e., lingering effects of the pre-change

[parafoveally confusable] item).

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 44

Figure 2. Processing times (ms) for Experiment 1a, which examined parafoveal confusability.

(A) An illustration of the orthographic confusability condition Previous analysis. The eye

symbol indicates the item measured. (B) Mean estimated coefficient exponential values

(ms) for each group in the orthographically non-confusable and confusable conditions

Note. * p < .05.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 45

Figure 3. Foveal confusability manipulation experiment: Illustrative example of NEXT

and PREV analyses (orthographic-confusable and non-confusable conditions).

Note. The symbol denotes the eye position (pre- and post- display change) in

addition to the item (n or n+1) measured (processing times and eye-voice spans). NEXT

analyses indicate the influence of foveal information from the second item (n+1),

affecting processing of the first item (n) late in its identification (eye-voice span measure

only). PREV analyses indicate the influence of the first item (n) on the processing of the

second item (n+1).

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 46

Figure 4. Processing times (ms) for Experiment 1b, which examined foveal confusability.

(A) An illustration of the orthographic confusability condition Previous analysis. The eye

symbol indicates the item measured. (B) Mean estimated coefficient exponential values

(ms) for each group in the orthographically non-confusable and confusable conditions.

Note. * p < .05.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 47

Figure 5. Eye-voice spans for Experiment 1b, which examined foveal confusability.

(A) An illustration of the phonological confusability condition, Next and Previous

analyses. The eye-voice symbol indicates the item measured. (B) Mean estimated

coefficient exponential values (ms) for each group in the phonologically non-confusable

and confusable conditions.

Note. * p < .05.

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RUNNING HEAD: RAPID NAMING AND DYSLEXIA 48

Appendix A

Standard deviations (log values) of random effects variables in Experiment 1a.

Variable Phonological Orthographic

Processing time Eye-voice Processing time Eye-voice

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

NEXT-

confusable

PREV-

confusable

Participant 0.20 0.19 0.14 0.17 0.20 0.21 0.15 0.17

Item 0.03 0.01 0.02 0.04 0.00 0.00 0.00 0.04

Character 0.03 0.08 0.04 0.19 0.04 0.04 0.06 0.18

Other-item 0.05 0.05 0.06 0.05 0.03 0.03 0.03 0.04

Residual 0.37 0.45 0.34 0.36 0.38 0.38 0.11 0.35

Standard deviations (log values) of random effects variables in Experiment 1b.

Variable Phonological Orthographic

Processing time Eye-voice Processing time Eye-voice

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

PREV-

confusable

NEXT-

confusable

Participant 0.21 0.19 0.19 0.17 0.30 0.17 0.18 0.14

Item 0.06 0.03 0.07 0.13 0.00 0.00 0.05 0.01

Character 0.03 0.10 0.07 0.19 0.04 0.08 0.21 0.05

Other-item 0.07 0.02 0.06 0.05 0.03 0.05 0.03 0.04

Residual 0.39 0.19 0.38 0.42 0.36 0.42 0.36 0.31