Spatial Orienting of Attention in Dyslexic Adults using Directional and Alphabetic Cues

■ Spatial Orienting of Attention inDyslexic Adults using Directional andAlphabetic CuesJeannie Judge1*,†, Paul C. Knox2 and Markéta Caravolas3,†

1School of Psychology, University of Central Lancashire, Lancashire, UK2Division of Orthoptics, University of Liverpool, Liverpool, UK3School of Psychology, Bangor University, Bangor, UK

Spatial attention performance was investigated in adults with dyslexia. Groups with andwithout dyslexia completed literacy/phonological tasks as well as two spatial cueing tasks,in which attention was oriented in response to a centrally presented pictorial (arrow) oralphabetic (letter) cue. Cued response times and orienting effects were largely similar indyslexic and nonimpaired readers. The one distinct pattern that emerged showed dyslexicadults to have smaller orienting effects in the right than left visual field for letter cues,whereas typical readers showed the opposite pattern. These smaller orienting effectsappeared to characterize the dyslexic group as a whole and not only one or two individuals.Our results suggest that dyslexic adults may have a subtle impairment in orienting visualattention when processing alphabetic (but not pictorial) cues. Several interpretations ofthese findings are considered, including links with a phonological deficit and/or a difficultyin shifting attention in the direction of reading. Copyright © 2013 John Wiley & Sons, Ltd.

Keywords: spatial orienting; attention; dyslexia; costs/benefits; phoneme awareness

Developmental dyslexia is typically characterized by persistent and universalphonological impairments (e.g. Bruck, 1992; Caravolas, Volín, & Hulme, 2005;Paulesu et al., 2001; Silani et al., 2005; Ziegler, Perry, Ma-Wyatt, Ladner, &Schulte-Körne, 2003), as estimated by various measures of phonological processing,including phoneme awareness tasks (Ramus et al., 2003) and the widely used proxymeasure of nonword reading (e.g. Rack, Snowling, & Olson, 1992). In addition to theknown phonological impairments among dyslexic adults, it has been hypothesizedthat dyslexia is sometimes associated with a life-long visual attention deficit, althoughneither its prevalence nor its aetiology are yet well established (Vidyasagar &Pammer, 2010). Research evidence indicating attentional impairments amongdyslexic individuals has been mixed (Buchholz & Aimola Davies, 2007; Hari, Valta,& Uutela, 1999; Lacroix et al., 2005). Moreover, it has been argued that whereworse performance has been observed, this may reflect dyslexic individuals’difficulties with coordinating task demands (Badcock, Hogben, & Fletcher, 2008)rather than being a core (Buchholz & Aimola Davies, 2007) or a specific (Lum,Conti-Ramsden, & Lindell, 2007) deficit in dyslexia.

*Correspondence to: Jeannie Judge, School of Psychology, University of Central Lancashire, Lancashire,UK. E-mail: [email protected]

†The first and third authors contributed equally to the preparation of this manuscript.

Copyright © 2013 John Wiley & Sons, Ltd. DYSLEXIA 19: 55–75 (2013)

DYSLEXIAPublished online 25 March 2013 in Wiley Online Library(wileyonlinelibrary.com). DOI: 10.1002/dys.1452

Spatial Orienting of Attention

Spatial cueing tasks provide a method of probing attentional function. One well-utilized cueing paradigm is the covert spatial orienting task (Posner, 1980; Posner,Snyder, & Davidson, 1980) in which the predictive validity of a spatial cue ismanipulated. Cues are used to indicate the position of an upcoming target,inducing shifts of attention. These may be either exogenous (i.e. stimulus-driven),in which an automatic shift of attention is elicited in response to peripheral cueswith short stimulus onset asynchronies (SOAs; e.g. Posner, 1980; Theeuwes,1991), or endogenous, whereby shifts of attention are under volitional control(Jonides, 1981; Warner, Juola, & Koshino, 1990) and take longer to accomplish(e.g. Warner et al., 1990). Endogenous tasks have usually relied on longer SOAsand the presentation of central symbolic cues (such as directional arrows).Participants respond more quickly to validly cued than neutral trials showingbenefits in reaction times (RTs), and they respond more slowly to invalidly cuedthan neutral trials showing performance costs. Orienting effects (i.e. the differencebetween valid and invalid trials) represent the absolute effectiveness of the cue ineliciting a shift of attention.

Importantly, recent research has shown that performance on spatial cueingtasks depends to some extent on the nature of the cue (e.g. directional arrows,eye gaze, words and digits), its location (central and peripheral) and itspredictiveness (predictive and nonpredictive). Ristic and Kingstone (2006: alsoBonato, Priftis, Marenzi, & Zorzi, 2008—Experiment 1) contrasted central arrowand digit cues and found that both cue types produced orienting effects when cueswere predictive, as would be expected in typical endogenous cueing tasks.However, when the cues were nonpredictive (that is, they were as likely toprovide valid as invalid information about the location of the upcoming target),they failed to influence performance in the digit task but continued to boostresponse speed in the arrow task. Thus, participants seemed to be processingarrow cues in a faster, reflexive manner, whereas digit cues seemed to elicit avolitional (endogenous) attentional mechanism. In a study contrasting differentcue types, Gibson and Kingstone (2006) reported that word cues conveyingdirection (e.g. ‘left’ and ‘right’) elicited slower response times than did equallypredictive arrow cues. These authors argued that word cues require greatercomputational and attentional resources to be interpreted because they entailsemantic processing, which is not required with ‘deictic’ cues such as arrows. Suchstudies place digit, word and presumably letter cues firmly within the domain ofendogenous orienting. Notably, such alphanumeric cues should also be stronglyassociated with automatically activated phonological codes, at least in typicalpopulations (Blau, Van Atteveldt, Ekkebus, Goebel, & Blomert, 2009; Ziegler,Pech-Georgel, Dufau, & Grainger, 2010).

In the present study, we contrasted central, informative arrow cues withcentral, informative letter cues, to further explore whether adults responddifferently to purely endogenous cues than to cues that may additionally activate aproposed reflexive attentional mechanism. Importantly, the inclusion of letter cuesallowed us to assess, in populations with and without prevalent phonological deficits,the extent to which spatial attention may be modulated by phonological processing(e.g. Wolf & Bowers, 1999). Dyslexic adults have difficulties processing not onlyletter strings (Hawelka, Huber, &Wimmer, 2006; Pitchford, Ledgeway, & Masterson,

56 J. Judge et al.


2009; Ziegler et al., 2010) but also single letters (e.g. Blau et al., 2009). These findingsare corroborated by behavioural and neuroimaging studies, which reveal thatwhereas in typical readers, letter–sound associations become automatic by latechildhood, dyslexic individuals persistently fail to acquire automatic associationsbetween these representations into adulthood (Blau et al., 2009; Froyen, Willems,& Blomert, 2010). Thus, we hypothesized that dyslexic adults (but not controls)may respond less effectively to letter cues than to arrow cues.

Spatial Orienting in Dyslexia

Atypical behaviour among dyslexic adults in orienting attention to exogenous cues,sometimes with visual field asymmetries, has been reported in several studies usingvariations on the Posner task. For example, Buchholz and Aimola Davies (2005)found that adults with dyslexia had difficulty shifting attention exogenouslybetween objects in the left visual field. Using a spatial cueing task combined witha visual search task, Roach and Hogben (2004, also 2007, 2008) demonstrated thatdyslexic adults were unable to take advantage of briefly presented spatial cues inorder to improve performance in discriminating the direction of a target;however, visual field differences were not probed in these studies. In research withdyslexic children, Facoetti et al. (2006) found that subgroups with impairednonword reading lacked attentional inhibition to uncued targets in the right visualfield and were slower at orienting attention in both visual fields at a very shortcue-stimulus SOA (100ms), although this difference had resolved at 250msSOA (Facoetti, Corradi, Ruffino, Gori, & Zorzi, 2010).

Less attention has been devoted to examining endogenous orienting in dyslexia,although there is some evidence of impairment from the developmental literature.Facoetti, Paganoni, Turatto, Marzola, and Mascetti (2000) found children withdyslexia to respond more slowly on cueing tasks using central cues and to alsoshow larger orienting effects in the left (95ms) than right (49ms) visual field incomparison with typical readers. Dyslexic children were also shown to producelonger response times to invalid cues in the left than right visual field in contrastto typical readers (Facoetti, Turatto, Lorusso, & Mascetti, 2001). It is difficult todraw strong conclusions about the prevalence of dysfunction in endogenousorienting of attention in dyslexia because the literature is sparse and the taskspecifications have varied greatly in the reported studies. Thus, an important aim ofour study was to add to the evidence base on the issue of asymmetrical performanceusing a spatial cueing task. If the asymmetrical pattern of larger orienting effects in theleft than right visual field, which has been observed in childhood dyslexia (Facoettiet al., 2001), is robust and persistent, we would also expect dyslexic adults to showlonger RTs on invalid trials in the left than right visual field. It is also noteworthy,however, that Facoetti et al. (2006) emphasized, on the basis of their study withchildren, that smaller orienting effects may also indicate attentional deficits, becausethey may reveal less efficient use of cue information. Thus, according to the currentliterature, an attentional impairment may manifest in larger or smaller orientingeffects, although it is not clear what might drive these different manifestations orin whom.

In the aforementioned study of Facoetti et al. (2006), exogenous visual attentionimpairments were linked to selective nonword reading impairments in children,leading to the suggestion that focused visual attention is a critical component of

Spatial Orienting in Dyslexia 57


sublexical graphemic parsing, which is required in nonword reading and is impairedamong dyslexic individuals. Accordingly, Facoetti et al. (2006) proposed theinteresting argument that visuoattentional deficit manifests only in subtypes ofdyslexic individuals with a nonword reading deficit (but not with a generalizedphonological deficit). We investigated the generality of visuoattentional deficitsamong English speaking dyslexic adults, who typically show both nonword readingand more general phonological impairments (e.g. Judge, Caravolas, & Knox, 2007;Ramus et al., 2003).

Spatial Orienting and Reading in Dyslexia

Endogenous covert shifts of attention are of particular importance in reading.According to the influential E–Z Reader model of eye movement control(Reichle, Rayner, & Pollatsek, 2003; Reichle, Warren, & McConnell, 2009), readinginvolves serial processing in which typical readers allocate attention sequentially toone word at a time and word meanings are accessed in order. This means thatwhile one word is being currently fixated, a leftward–rightward shift of covertattention is made to the next word. This assumption of the model is supportedby the literature; however, we note that a strong contender to the E–Z Readeris the SWIFT model (Engbert, Nuthmann, Richter, & Kliegl, 2005) and that thislatter model argues in favour of parallel processing and that word meanings donot have to be accessed in order. A thorough discussion of these models is beyondthe scope of this paper. There is evidence to suggest that the perceptual span islarger to the right of fixation and that readers gain benefit from parafoveal wordsduring reading (see Rayner, 1998 for a review). Turning to dyslexic readers, thereis some evidence to suggest that the perceptual span may be atypical in dyslexia(Prado, Dubois, & Valdois, 2007; Rayner, Murphy, Henderson, & Pollatsek, 1989)and that dyslexic readers make smaller saccades during reading (Rayner, 1998). Thus,smaller saccades are associated with text-reading difficulty (e.g. Rayner, Fischer, &Pollatsek, 1998), and this in turn may be associated with smaller or atypical covertshifts of attention. On the basis of the eye movement literature, then, it is reasonableto hypothesize that dyslexic readers may make smaller or atypical covert shifts ofattention during reading and this may manifest in their performance on endogenouscueing tasks that involve letter cues. If this is the case, we may expect those withdyslexia to have more difficulty with covert shifts of attention in response to lettercues than for arrow cues. In turn, such a difficulty may be more apparent in the rightvisual field for letter cues similarly to the shifts of attention that are required inreading where leftward–rightward shifts of covert attention are more prevalent.We would expect any impairment in covert endogenous shifts of attention toconstrain the amount of visual information that can be taken in on a given fixationduring text reading among dyslexic individuals.

Aims and Predictions

Using the Posner paradigm in conjunction with eye tracking technology, the mainaim of the present study was to examine whether dyslexic adults were impaired inspatial orienting in comparison with IQ matched controls. We hypothesized that ifdyslexic readers were impaired in general orienting behaviour, then they shouldshow slower RTs and deficits in orienting effects for both arrow and letter cues,

58 J. Judge et al.


relative to controls. Our second aim was to explore whether dyslexic individualsexperienced greater difficulties with letter than directional arrow cues. Thispattern would be expected given dyslexic individuals’ known difficulties processingstimuli strongly associated with phonological codes (Blau et al., 2009; Ziegler et al.,2010) and would also be consistent with the view that the perceptual span inreading may be atypical in dyslexia (Prado et al., 2007; Rayner et al., 1989). Thismay manifest in terms of longer RTs or atypical orienting effects. An additionalaim was to investigate whether dyslexic adults showed visual field asymmetrieson the cueing task, with particular orienting impairments in the left visual field(cf. Bonato et al., 2008). Finally, we examined whether any observed groupdifferences were driven by a few outliers or whether they represented homogenousbehaviour in each group.

METHOD

Participants

Twelve adults with dyslexia (four men and eight women) and 12 skilled readers(two men and 10 women) were recruited from a university population in theNorth West of England. Individuals with dyslexia had received a diagnosis from aqualified psychologist or education authority official prior to recruitment butimportantly had not been diagnosed with any other developmental disorder(e.g. ADHD or dyspraxia) or any neurological or psychiatric disorder. Sixparticipants had been diagnosed with dyslexia in childhood, and the remainingparticipants received a formal diagnosis in adulthood, as students, through theUniversity’s Student Services unit. For the present study, all participantscompleted a psychometric battery, including tests of reading, spelling andphonological skills.

A prerequisite for inclusion in the study for all participants was that full-scale,verbal and performance IQ (PIQ) were equal to or greater than 90. The specificcriterion for inclusion of dyslexic individuals was that they showed a concurrentdiscrepancy between PIQ and their literacy skills (reading and/or spelling). Allthe dyslexic participants showed a discrepancy between PIQ and spelling, whichvaried in magnitude from 17 points to 52 standardized points, yielding discrepanciesexceeding 1 standard deviation and, in many cases, up to 3 standard deviations. Incontrast, the difference in standardized points for controls ranged from 2 to 10points (all within 1 standard deviation of that of their PIQ); thus, there was nooverlap in spelling performance for any control and dyslexic participants. Withrespect to word-level reading, the discrepancy ranged from 9 to 37 points in thedyslexic group—with only one dyslexic participant showing no discrepancy betweenPIQ and reading. For controls, all scores were within 1 standard deviation of theirPIQ (range: 1–9 points). The literacy profiles observed in our dyslexic sample aretypical for dyslexic adults in university education.

The groups were closely matched for age (controls: M= 20.58, SD= 1.62,dyslexic readers: M= 20.92, SD= 1.38), F(1,22) = 0.29, MSE= 2.27, p= .59, andfull-scale, verbal and performance IQ (Table 1). One control participant was lefthanded, but all the remaining participants were right handed. All participants wereEnglish monolinguals, and all had normal or corrected to normal visual acuity.



Testing took place in two sessions lasting approximately 1.5 h each. The psycho-metric and phonological processing tasks were administered individually to eachparticipant during the first testing session. Participants who met the selectioncriteria returned to the laboratory on a separate occasion to complete the spatialcueing tasks.

Psychometric Tests

The Wechsler Abbreviated Scale of Intelligence (Wechsler, 1999) was used toassess general intelligence; this yielded a full-scale, verbal and performance IQ foreach participant. Subtests from the Wechsler Adult Intelligence Scale (Wechsler,1998) were used to assess verbal short-term memory skills (Digit Span) and speedof processing (Digit Symbol Coding, Symbol Search and Copy Speed). Single(unspeeded) word reading and spelling were computed using the Wide RangeAchievement Test (WRAT-3, Jastak & Wilkinson, 1993), and nonword readingwas measured using the word attack subtest from the Woodcock Reading MasteryTests – Revised (Woodcock, 1998). Exception word reading was measured withthe word list of Castles and Coltheart (1993). All psychometric and literacy taskswere administered in accordance with published guidelines.

Phonological Processing Tasks

Phonological processing skills were measured with nonword spoonerisms,phoneme deletion and a rhyme fluency task. These tasks have been reported inmore detail in our previous work (Judge et al., 2007); therefore, only a briefdescription is provided here. On the spoonerism task, participants transposed the

Table 1. IQ, literacy and psychometric scores (mean and standard deviation) and ANOVA results for12 skilled readers and 12 dyslexic readers

Performance measure Controls Dyslexic readers ANOVA results

IQ measures (WASI)Full-scalea 113.92 (5.23) 115.25 (5.94) F= 0.34, p= .57Verbala 110.58 (5.12) 109.67 (7.75) F= 0.12, = .74Performancea 113.08 (6.33) 119.00 (8.19) F= 3.92, p= .06

WRAT Readinga 112.33 (3.67) 98.58 (7.96)*** F= 29.51, p< .001WRAT Spellinga 111.75 (6.07) 89.17 (10.76)*** F= 40.07, p< .001Nonword readingb 39.08 (2.61) 31.55 (3.67)*** F= 32.67, p< .001Exception word readingb 28.75 (0.86) 25.82 (1.88)** F= 23.61, p< .001WAIS-III measuresDigit Spanc 11.42 (2.93) 8.55 (2.16)* F= 7.02, p= .02Symbol Searchc 12.17 (1.74) 10.33 (2.87) F= 3.57, p= .07Digit Symbol Codingc 12.00 (1.95) 9.67 (1.87)** F= 8.91, p= .01Processing Speeda 111.50 (8.05) 99.92 (10.68)** F= 9.00, p= .01Copy b 126.17 (11.01) 122.18 (11.92) F= .70, p= .41

WASI, Wechsler Abbreviated Scale of Intelligence; WRAT, Wide Range Achievement Test; WAIS-III, Wechsler Adult Intelli-gence Scale.aStandard scores are reported that are based on a population mean of 100 and a standard deviation of 15.bRaw scores are reported for nonword reading, exception reading and copy speed. The scores for nonword and exception wordreading as well as digit span and copy speed are based on 11 dyslexic participants due to a loss of data.cScaled scores are reported that range from 1 to 19 with a mean of 10.*p< .05; **p< .01; ***p< .001.

60 J. Judge et al.


initial phonemes for nonword pairs that contained either singleton onsets (Block 1)or cluster onsets (Block 2). The test was scored for accuracy (across both blocks upto a maximum score of 36). On the phoneme deletion task, participants deleted eitherthe second (Block 1) or penultimate (Block 2) phoneme from aurally presentedmonosyllabic nonwords and reported the appropriate response. The test wasscored for accuracy (up to a maximum of 20) and latency (mean response time inms per item) using sound editing software (Cool Edit, 2000). Finally, a rhyme fluencytask was administered (after Snowling, Nation, Moxham, Gallagher, & Frith, 1997) inwhich participants generated words or nonwords that rhymed with four differenttargets words.

Spatial Cueing Task

The visual targets were small black squares presented against a light backgroundand were presented to participants’ left visual field (LVF) or right visual field(RVF). Cues were either directional arrows (height: 0.4�) or single letters (height:0.5�). All stimuli were generated by a Cambridge Research Systems Visual StimulusGenerator 2/5 (VSG) and presented on a visual display unit. A VSG button boxwas used to collect manual reaction times. Participants were seated 57 cm fromthe visual display with their head stabilized by a chin rest to reduce head movements.Viewing was binocular, and horizontal eye movements were monitored from the lefteye using an infrared corneal reflection device (IRIS, Skalar Medical, Delft,Netherlands). The purpose of this was to encourage participants to maintain stablefixation throughout the task and to detect those trials on which they executed eyemovements or blinks during the task.

Each trial began with the appearance of a small fixation cross that was presented inthe centre of the monitor for a variable period (500–1500ms). Two boxes werethen presented peripherally, one on either side of the fixation cross. The boxesappeared 6.5� from fixation and had a side of 1.7�. After 500ms, the cue waspresented centrally (i.e. 0.7� below the fixation cross) for 100ms. Following theappearance of the cue, the target (a small black square) was presented in eitherthe right (RVF) or left (LVF) box. The SOA varied pseudorandomly (600–1000ms);therefore, the interval between the offset of the cue and the onset of the target couldnot be predicted by participants, and the intertrial interval ranged between 800 and1000ms. Neutral trials were not informative about target location. Participantsresponded to the onset of the target with a button press.

Participants completed four blocks of trials in a counterbalanced order, and eachblock comprised 128 trials. Arrow and letter cues were used in two blocks of trials.Arrow and letter cues were presented in separate blocks, and targets appeared inboth visual fields equally. For the task involving arrow cues, a directional arrowheadpointing to the left or right! indicated where attention should be oriented oninformative trials. However, on neutral trials, two arrowheads, !, werepresented centrally pointing to both the left and right sides simultaneously indicatingthat the target was just as likely to appear on the left as on the right. In the letter-cuecondition, single letters were presented centrally (0.7� below the fixation cross) inuppercase. The letter [L] was used to denote that attention should be oriented tothe left, and the letter [R] was used to indicate that attention should be orientedto the right; the letter [N] was used for neutral trials and indicated that the targetwas equally likely to appear on either side of fixation.



On each block of trials, there were 16 neutral trials (8 left and 8 right), 16 invalidtrials (8 left and 8 right) and 96 valid trials (48 left and 48 right). Thus, of the informa-tive trials, 86% were valid and 14% invalid. Trials were also equally distributedbetween the visual fields for valid and neutral conditions.

Procedure

Participants were familiarized with the task and received both verbal instructionsand an on-screen computer demonstration of the task. They were instructed touse the cues to try and predict the location of the target thereby speeding up theirreaction time and were told to respond to the target by pressing the manualreaction time button with their dominant hand. They were further instructed tokeep their eyes still throughout the task.

RESULTS

Psychometric Assessment

The group with dyslexia showed a larger discrepancy in standard score unitsbetween their PIQ and WRAT spelling scores than controls (controls: M= 1.33,SD= 7.55; dyslexic readers: M= 29.83, SD= 12.45), F(1,22) = 45.89, MSE= 106.20,p< .001, �p

2 = .68; a similar pattern was observed for the difference between PIQand WRAT word reading (controls: M= .75, SD= 5.31; dyslexic readers:M= 20.42, SD= 11.06), F(1,22) = 30.85, MSE= 75.24, p< .001, �p

2 = .58. Meanscores, standard deviations and ANOVA results for the IQ, literacy and otherpsychometric tests are presented in Table 1, demonstrating that the groupshad similar IQ scores but that the group with dyslexia had poorer literacy skillsthan controls.

Phonological Processing Skills

Mean scores, standard deviations and ANOVA results for the phonologicalmeasures are presented in Table 2 showing that the group with dyslexia performed

Table 2. Mean scores (standard deviation) and ANOVA results for the phonological processing tasks(n= 12 skilled readers, n= 12 dyslexic readers)

Phonological task Controls Dyslexic readers ANOVA results

Spoonerisms accuracy 27.25 (3.04) 18.64 (5.55)*** F= 21.77, p< .001Phoneme deletion accuracy 19.33 (0.77) 16.64 (2.54)** F= 12.31, p= .002Phoneme deletion latencyCombined measurea 0.340 (0.159) 4.760 (2.928)*** F= 20.25, p< .001

Rhyme fluency 45.73 (13.94) 28.18 (8.36)** F= 12.81, p= .002

aPhoneme deletion latency measured in seconds and aggregated across phoneme position (i.e. the average for Blocks 1 and 2).Analysis of the separate Blocks demonstrated the same pattern as that for the combined measure. Spoonerisms, deletion accu-racy, deletion latency and rhyme fluency are based on 11 dyslexic participants. Rhyme fluency is based on 11 controls and deletionlatency is based on nine controls due to a loss of data.**p< .01; ***p< .001.

62 J. Judge et al.


significantly less well than controls on every measure of the phonological skills bat-tery. While the homogeneity of variance assumption was not satisfied for the literacyand phonological measures, nonparametric tests demonstrated the same results.

Spatial Cueing Task

Data for arrow cues and letter cues were combined across blocks. Mean reactiontimes were calculated for each participant for each visual field (LVF and RVF), cuecondition (valid, invalid and neutral) and cue type (arrow and letter). Reactiontimes that were faster than 100ms were removed as they were considered tobe anticipatory, and those that were longer than 1000ms were removed as theywere considered to be long outliers and not stimulus driven. Following this, anyreaction times that were longer than 2.5 standard deviations from each partici-pant’s individual mean were removed. This led to the removal of very few datapoints (less than 2% for any participant). Two participants with dyslexia werestatistical outliers such that their mean reaction times across all conditions weremore than 2.5 standard deviations longer than that of the respective group mean.Therefore, their data were not included in the ensuing analyses, and the followingRT analyses are based on 12 controls and 10 participants with dyslexia. For thepurpose of reliability, the trials in which either an eye movement or blink wasdetected were retained for this analysis (see section on Eye Movement Analyses).The group means and standard deviations for the spatial cueing task are detailedin Table 3.

To explore whether typical and dyslexic readers approached the task differ-ently, the data for each group were analysed separately. The data from the controlgroup were subjected to a three-way within-participants ANOVA with visual field(left versus right), cue condition (valid, neutral or invalid) and cue type (arrowsversus letters) as the factors. The main effect of cue condition reached significance,F(2,22) = 28.770, MSE= 1624.605, p< .001, �p

2 = .72; however, the main effectsof visual field, F(1,11) = 3.094, MSE = 893.674, p = .11, �p

2 = .22, and cue type,F(1,11) = .01, MSE=1471.128, p= .92, �p

2 = .00, as well as all the two-way interac-tions failed to reach significance. A significant three-way interaction between visualfield, cue condition and cue type emerged, F(2,22) = 3.528, MSE=807.094,p= .047, �p

2 = .24. As orienting effects (i.e. the difference between valid and invalidRTs) represent the effectiveness of the cue for informative trials, planned compari-sons focused on these trial types. The results revealed that typical readers respondedfaster on valid than invalid trials, thereby demonstrating significant orientingeffects for arrow cues in the left, t(11) =�6.545, p< .001, and right visual fields,t(11) =�4.387, p = .001; this pattern was also observed for letter cues in the left,t(11) =�3.705, p= .003, and right visual fields, t(11) =�4.238, p= .001. The interac-tion reflected the fact that the pattern of the orienting effects between the left andright visual fields differed for arrow and letter cues; that is, whereas typical readersshowed an orienting effect of 79ms for arrow cues in the left visual field and 51msfor arrow cues in the right visual field, this pattern was reversed for letter cues aslarger orienting effects were observed in the right (69ms) than left (49ms).

Turning to the analysis for the dyslexic group, their data were also subjected toa three-way within-participants ANOVA with visual field, cue condition and cuetype as the factors. Similar to the control group, a significant main effect of cuecondition was observed, F(2,18) = 43.723, MSE= 525.306, p< .001, �p

2 = .83,



Table3.

Meanreactio

ntim

es(standarddeviation)

show

nin

msforvalid,invalid

andneutralcue

condition

sforarrow

andletter

cues

(n=12

skilled

readers,n=10

dyslexicreaders)

Targetlocatio

n

LVF

RVF

Cue

type

Valid

Neutral

Invalid

Valid

Neutral

Invalid

Con

trols

Arrow

s280.08

(35.97)

313.92

(46.34)

359.92

(59.32)

276.50

(42.72)

310.33

(56.73)

327.00

(41.87)

Letters

290.67

(46.49)

311.67

(65.02)

339.75

(42.86)

282.42

(47.25)

295.83

(50.04)

351.33

(63.92)

Dyslexicreaders

Arrow

s267.70

(20.07)

283.40

(18.15)

329.00

(35.96)

267.40

(25.82)

289.60

(21.76)

315.50

(25.46)

Letters

269.00

(19.41)

289.60

(52.45)

329.30

(51.13)

270.40

(31.64)

288.60

(48.56)

291.20

(39.27)

LVF,leftvisualfield;

RVF,rightvisualfield.

64 J. Judge et al.


whereas the main effects of visual field, F(1,9) = 1.605, MSE= 1065.390, p= .24,�p

2 = .15, and cue type, F(1,9) = .103, MSE= 1706.856, p= .76, �p2 = .01, did not

reach significance. In contrast to the control group, a significant two-way interactionemerged between visual field and cue condition, F(2,18) = 6.546, MSE=383.179,p= .007, �p

2 = .42; however, none of the remaining interactions reached significanceincluding the three-way interaction between visual field, cue condition and cue type,F(2,18) = 1.030, MSE=434.451, p= .38, �p

2 = .10. The visual field by cue conditioninteraction revealed that dyslexic readers made faster responses for invalid cues inthe right (M=303ms) than left (M=329ms), t(9) =3.210, p= .01, but responses werenot significantly different between the visual fields for either valid, t(9) =�.111,p= .91, or neutral cues, t(9) =�.268, p= .80. To draw comparisons with typicalreaders, we examined the visual orienting effects for arrow and letter cues. Thisallowed us to assess if the orienting patterns in the dyslexic group were similar tothose of typical readers. Our dyslexic group showed significant orienting effectsfor both cue types and visual fields, but the pattern of these differed to that of typicalreaders for letter cues. For arrow cues, dyslexic readers showed an orienting effectof 61ms in the left visual field, t(9) =�6.770, p< .001, and 48ms in the right visualfield, t(9) =�7.538, p< .001—this pattern is similar to that of typical readers. Turn-ing to letter cues, we found that dyslexic readers showed an orienting effect of 60msin the left visual field, t(9) =�4.356, p= .002, but an orienting effect of only 21ms inthe right visual field, t(9) =�3.185, p= .01. Thus, dyslexic readers showed a smallerorienting effect in the right visual field in response to letter cues suggesting they wereless able in using the cue. This is further supported by the observation that in theright visual field, response times were similar for neutral and invalid letter cues fordyslexic readers, whereas in the left visual field, the group was around 40ms fasterfor neutral than invalid cues.

Individual Differences in Visual Orienting Behaviour

We considered that the cueing asymmetry observed in the right visual field forletter cues might not characterize the entire dyslexic group. To examine theextent to which individuals with and without dyslexia showed different cueingbehaviour, we calculated the magnitude of the orienting effects for all participantsfor arrow and letter cues in both visual fields. We focus here on orienting effectsas this represents the difference in response time for informative cues. These dataare illustrated in Figure 1. It is clear from inspection of Figure 1A that although theorienting effect is variable amongst both groups, all participants are showing somedegree of orienting effect (i.e. have values above 0) for targets in the left visual fieldfor arrow cues. Moreover, the percentage of participants showing an orientingeffect that was 1 standard deviation below the control group mean was similarfor the groups (controls, 25%; with dyslexia, 27%). Similarly, Figure 1B shows thatwith the exception of one control participant, all individuals used the predictivecues to shift attention in the right visual field for arrow cues. All the dyslexicparticipants performed within 1 standard deviation of the control group mean,but two controls were impaired using this criterion. Although the orienting effectfor letter cues in the left visual field does not appear remarkable (Figure 1C), twocontrols and one dyslexic participant showed an orienting effect that was below 1standard deviation of the control group mean. A different pattern emerged forletter cues in the right visual field; Figure 1D shows that similar numbers of controls



as dyslexic readers showed no orienting effect (n= 2 for each group) and thepercentage of participants performing below 1 standard deviation of the controlgroup mean was similar (controls, 25%; with dyslexia, 27%). However, there was atrend for individual dyslexic readers to show smaller orienting effects for thiscomparison than controls. Thus, the small orienting effect in the right visual fieldfor letter cues among dyslexic readers does not seem to be driven by a small numberof outliers but is representative of the group as a whole. This suggests that dyslexicreaders needed longer to process the letter cue for it to elicit an endogenous shift ofattention. In contrast, the individual performance for arrows cues was much betteracross groups in that larger orienting effects were shown, which were possiblyattributable to the longer SOAs and the putative reflexive component of the cues.

Eye Movement Analyses

As covert shifts of attention are based on the premise that attention is moved toanother location in the absence of eye movements and dyslexic readers have beenreported to have unstable fixation (Eden, Stein, Wood, & Wood, 1994; Fischer &Hartnegg, 2000), we wished to explore whether dyslexic and typical readersdiffered in the number of eye movements or blinks made during the task. Theprecise nature of the eye movement set-up meant that the specific parameter ofsaccade latency could not be analysed. Although the programme recorded

A. Orienting Effect for Arrows in LVF

C. Orienting Effect for Letters in LVF

B. Orienting Effect for Arrows in RVF

D. Orienting Effect for Letters in RVF

Ori

enti

ng

Eff

ect

in m

s

Controls Dyslexic Readers Controls Dyslexic Readers-50

-25

0

25

50

75

100

125

150

Ori

enti

ng

Eff

ect

in m

s

-50

-25

0

25

50

75

100

125

150O

rien

tin

g E

ffec

t in

ms

Controls Dyslexic Readers Controls Dyslexic Readers-50

-25

0

25

50

75

100

125

150

Ori

enti

ng

Eff

ect

in m

s

-50

-25

0

25

50

75

100

125

150

Figure 1. Orienting effect (in ms) for individual control (n= 12) and dyslexic (n=11) participants.Figure 1A shows the orienting effect for targets in the left visual field for arrow cues, and Figure 1Bshows the orienting effect for targets in the right visual field for arrow cues. The corresponding datafor letter cues are shown in Figure 1C (left visual field) and Figure 1D (right visual field). The horizontal

line through the data points represents the mean for each group.

66 J. Judge et al.


deviations from fixation, it did not differentiate between eye movements and blinksduring the task. Therefore, we compared the percentage of trials in which such adeviation was made to explore the extent to which the groups maintained stablefixation, particularly as the task included SOAs that were sufficiently long toexecute a saccade. The percentages of eye movements or blinks for the twogroups for all conditions are shown in Table 4. The data from the arrow and lettercues were analysed separately. The 3 (cue condition)� 2 (visual field)� 2 (group)mixed ANOVA for the arrow data revealed that the main effect of group was notsignificant, F(1,21) = .31, MSE= 1044.24, p= .59, �p

2 = .01, neither were the maineffects of cue condition, F(2,42) = .16, MSE= 66.34, p= .85, �p

2 = .01, or visual fieldF(1,21) = .45, MSE= 66.85, p= .51, �p

2 = .02. All the interactions failed to reachsignificance. A similar pattern emerged with the data from the letter cues in thatthe main effect of group was not significant, F(1,21) = 1.11, MSE= 1524.16,p= .31, �p

2 = .05, and all other effects failed to reach significance. These resultsconfirm that typical readers were just as likely to blink or execute an eye movementas dyslexic readers.

Finally, we analysed the RT data in which all the trials in which either an eyemovement or blink was detected were removed in order to cross-validate ourmain findings. This analysis was based on fewer trials as both groups were proneto blinks or eye movements during the task, but it does represent pure shifts ofcovert attention (Table 5). A four-way mixed ANOVA with reading group asthe between-participants factor was conducted, and only the main effect of cuecondition reached significance showing the typical validity effects, F(2,40) = 45.42,MSE= 1292.79, p< .001, �p

2 = .69. Nevertheless, a univariate ANOVA revealedthat the orienting effect for the right visual field letter cue condition wassmaller for the dyslexic group (M= 24ms) than the control group (M = 65ms),F(1,20) = 5.07, MSE = 1796.13, p = .04, �p

2 = .20. The data remain consistent withthe earlier analysis in that dyslexic readers showed similar RTs for the invalid andneutral conditions in the right visual field in response to a letter cue suggestingthat they were not able to use the cue as efficiently as controls.

DISCUSSION

We compared visual attention performance in adults with and without dyslexiausing two cue types and examined visual field effects as well as their distributionswithin each group. Although the dyslexic group showed comparable performancewith controls for verbal, performance and full-scale IQ, they demonstratedsignificantly poorer performance on all literacy measures. Accordingly, the individualprofiles of all dyslexic participants showed a discrepancy between their IQ andliteracy performance. In addition, dyslexic participants showed impaired perfor-mance on all the phonological measures including nonword reading even though theywere not recruited on this basis, supporting the robustness and persistence of thisdeficit in an adult sample (Bruck, 1992).

Similarities and Differences Between Groups on Visual Attention

Our first important finding on the cueing task was that typical and dyslexic readersboth showed a similar pattern of orienting effects for symbolic arrow cues—that



Table4.

Meanpercentage

eyemovem

enterrors

a(stand

arddeviation)

forvalid,invalid

andneutralcue

condition

sforarrow

andletter

cues

(n=12

skilled

readers,

n=11

dysle

xicreaders)

Targetlocatio

n

LVF

RVF

Cue

type

Valid

Neutral

Invalid

Valid

Neutral

Invalid

Con

trols

Arrow

s21.96(14.82)

20.33(14.91)

19.13(14.15)

20.53(14.29)

20.38(19.48)

22.03(16.61)

Letters

19.64(17.18)

26.08(23.15)

26.08(23.15)

25.61(17.00)

23.51(19.42)

23.87(15.88)

Dyslexicreaders

Arrow

s23.14(10.16)

21.12(9.94)

25.00(12.16)

25.44(10.19)

26.82(22.50)

21.10(15.33)

Letters

29.06(14.64)

36.25(18.52)

24.81(20.42)

28.91(14.94)

32.23(16.81)

31.89(14.18)

a Errorspertainto

uncued

eyemovem

ents

and/or

blinks.



68 J. Judge et al.


Table5.

Meanreactio

ntim

es(standarddeviation)

show

nin

msforvalid,invalid

andneutralcue

condition

sforarrow

andletter

cues

(n=12

skilled

readers,n=10

dyslexicreaders)fortrialswith

eyemovem

ents/blinks

removed

Targetlocatio

n

LVF

RVF

Cue

type

Valid

Neutral

Invalid

Valid

Neutral

Invalid

Con

trols

Arrow

s279.33

(35.05)

316.50

(48.57)

352.42

(56.31)

274.83

(41.30)

313.00

(61.26)

326.67

(49.56)

Letters

290.67

(45.02)

312.25

(67.75)

334.58

(45.92)

278.83

(47.04)

299.83

(60.87)

344.08

(60.79)

Dyslexicreaders

Arrow

s266.80

(18.17)

285.30

(17.47)

330.20

(34.31)

266.00

(24.62)

288.10

(26.33)

314.30

(29.69)

Letters

270.80

(18.97)

289.50

(58.38)

315.60

(45.43)

268.40

(31.57)

295.20

(53.63)

292.80

(39.22)

The

dyslexicdata

arebasedon

n=10

dueto

astatisticalou

tlier.





is, orienting effects were larger in the left than right visual field. Thus, dyslexicreaders were as able as controls to orient their attention in response to symbolicarrow cues on a predictive cueing task. As both groups showed longer RTs for in-valid cues in the left than right visual field, this suggested that it was more difficultto disengage attention when it was miscued to the right than left visual field.Hence, right–leftward shifts were more difficult than leftward–rightward shiftsfor dyslexic participants and controls. Therefore, when cues were pictorial andhighly iconic, and presumably required only minimal linguistic processing, dyslexicadults were not impaired on a visual attention task and were able to orient theirattention similarly to age-matched and IQ-matched controls.

A somewhat different pattern of results emerged on the letter cue task.Whereas typical and dyslexic readers responded similarly to targets appearing inthe left visual field, whether the cue was valid or invalid, and hence also showedsimilar orienting effects in this hemifield, the groups’ behaviour differed inresponse to targets in the right visual field. Whereas typical readers showed largerorienting effects in the right than left visual field suggesting that the cue informationexerted a stronger influence in the right visual field, the dyslexic readers showed alarger orienting effect in the left than right visual field indicating that the cueinformation was less potent in the right visual field. Dyslexic readers showed verysimilar response times for neutral [N] (i.e. noninformative) and invalid cues in theright visual field suggesting that they were not using the cue information very wellin performing the task, whereas in the left visual field, RTs were 40ms faster forneutral than invalid cues. This suggested that the dyslexic group had no difficultyin using letter cues in the left visual field. To the extent that reduced orientingeffects indicate less effective use of the cue in eliciting a voluntary shift of attention(e.g. Facoetti et al., 2006), these results suggest a subtle and specific impairment incue use in the group with dyslexia.

Visual Field Asymmetries in Dyslexia

Dyslexic readers, like their nonimpaired counterparts, showed larger orientingeffects in the left than right visual field for arrow cues, suggesting that this is a‘normal’ attentional asymmetry. Also, dyslexic readers were not significantlyslower than controls on invalid trials in the left visual field for either arrow orletter cues. Thus, our findings do not indicate a left visual field impairment in dyslexicadults, but they replicate our previous results using a different cueing task( Judge et al., 2007) in which dyslexic adults did not show significant visual fielddifferences to briefly presented targets for either manual reaction times or saccadelatency. The present findings are not entirely consistent with the childhood dyslexialiterature on visual field asymmetries in which Facoetti and colleagues (2001, 2006)observed slower responses on the invalid cue condition in the left than right visualfield. Our significant two-way interaction revealed that dyslexic adults showed fasterRTs in the right than left visual field for invalid cues but not for valid and neutral cues.Faster RTs can indicate either a better performance or that individuals are not usingthe cue information (Facoetti et al., 2006). Thus, this pattern suggests that dyslexicindividuals had difficulty using the cue information in the right visual field when theyweremiscued to the left visual field. Inspection of Table 3 shows that RTs were fasterfor invalid letter cues in right than left visual field, providing an indication that thisgroup were less able to use letter cue information in the right visual field.

70 J. Judge et al.


We are not aware of other studies that have used letter cues; thus, directcomparisons with other findings are not possible. However, the impairment inthe right visual field for letter cues in our dyslexic adults is similar to the deficitobserved in dyslexic Italian children by Facoetti et al. (2006) using nonlinguisticstimuli. Specifically, Facoetti et al. reported that dyslexic children with a nonwordreading impairment did not show a cueing effect in the right visual field in compar-ison with dyslexic individuals with better nonword reading skills and normalcontrols. Working within a dual-route framework, the authors interpreted thisfinding to mean that the reading difficulties of dyslexic individuals with visualattention problems specifically manifest in impaired nonword reading becausenonword reading is achieved via the sublexical route, which requires in additionto phonological processing, a precise visuospatial processing mechanism for left-to-right graphemic parsing. Whereas our and the Italian results are partiallycompatible, the interpretation of Facoetti et al. fits our findings less well. First, inour study, the group with dyslexia showed weaker reading skills across allmeasures of reading; thus, the weak orienting effect was not limited to individualswith selective impairments in nonword reading. Second, the group with dyslexiademonstrated a weaker orienting effect with letter cues but not with arrow cues.It is not clear why the attentional mechanism should function differently inresponse to different stimulus types (arrow/letter) unless the stimulus typemoderates attentional behaviour. Accordingly, recent research suggests thatorienting attention to centrally presented, predictive arrow cues may benefit froma facilitatory interaction between endogenous and reflexive orienting (Ristic &Kingstone, 2006) and thus may be easier to accomplish than the more computation-ally taxing letter cues (Gibson & Kingstone, 2006). The discrepancy between ourstudy and that of Facoetti et al. with children may also reflect developmental effects,such that differences that are observed in childhoodmay be attenuated in adulthood,at least when nonalphanumeric cues are used.

A methodological factor that may have contributed to the good performance ofour dyslexic participants in the arrow condition was the SOA manipulation in thecurrent study. We manipulated the SOA pseudorandomly from 600 to 1000msacross all conditions; thus, the intervals were relatively long. SOA affects bothRTs and size of orienting effect (e.g. Bonato et al., 2008). Although orientingeffects are reported to remain stable for arrow and digit cues for SOAs from300 up to 900ms (Ristic & Kingstone, 2006), cueing effects seem to arise morequickly (as early as 100ms) for arrow cues than for digit and word cues (e.g. Bonatoet al., 2008; Gibson & Kingstone, 2006; Ristic & Kingstone, 2006). Our use ofrelatively long SOAs leaves open the possibility, then, that any performancedifferences that might have occurred at earlier stages of processing (e.g. between0 and 300ms) may have given enough time to the dyslexic participants to resolveany underlying lags in response times, thus obscuring earlier-occurring performancedifferences, in particular on the faster-processed arrow cues. This possibility,however, does not place in question the finding that dyslexic participants showedrelatively different orienting behaviour as a function of cue type at the longer SOAs.Our result for letter cues in dyslexic adults are compatible with the findings from theeye movement literature, which reports that dyslexic individuals make smallersaccades when reading (see Rayner, 1998 for a review). If we adopt the view thatreading involves covert, leftward–rightward shifts of attention prior to theexecution of saccades (see the E–Z Reader model of eye movement control by



Reichle et al., 2003, 2009), then dyslexic individuals may be less skilled in executingleftward–rightward shifts of attention in response to letter cues that activatephonological codes, as was the case for our dyslexic readers at the group and individ-ual levels. This is supported by the similar RTs for the invalid and neutral conditionfor letter cues in the right visual field and the small orienting effect—both of whichsuggest that dyslexic individuals were not using the cue to shift attention in theright visual field or that making a leftward–rightward shift was more sluggish thanright–leftward shifts. We also note that our result with letter cues might be a directconsequence of difficulty with covert shifts of attention independent of anyphonological problem in the dyslexic sample. That is, even when pure covert shiftsof attention were considered (having excluded eye movements and blinks), thedyslexic group showed a smaller orienting effect than controls for letter cues inthe right visual field in which the shift of attention was in the direction of reading.One possibility is that through their years of experience with reading and hence left-ward–rightward covert shifts of attention, typical readers have an advantage overdyslexic readers when the shifts of attention are in the direction of reading inresponse to letters or words. Typical readers may distribute their attentionasymmetrically in response to letter cues (as during reading), but not for arrow cues,as their perceptual span is larger to the right of fixation in contexts that sharefeatures with reading. On the other hand, dyslexic adults may show a more symmet-ric distribution for both types of cue because of their difficulties with covert attentionin the direction of reading. Although this hypothesis requires more direct investiga-tion and replication, it is supported by the fact that a smaller orienting effect in theright visual field for letter cues consistently emerged (even when potentially noisytrials due to eyemovements were removed from the analysis) for the dyslexic group.Taking into account the phonological profiles of our dyslexic participants, along withthe well-documented letter processing difficulties of this population in general,however, our preferred interpretation of the current results is that they are dueto a combination of less efficiently developed covert shifting of attention in tasksrequiring processing of phonographic information, compounded by a phonologicalimpairment. Future studies may be able to delineate these issues by concurrentlyassessing perceptual span in text reading, covert attention and phonological process-ing in dyslexic and typical readers.

CONCLUSIONS

Our findings demonstrate that dyslexic adults are able to use symbolic cues inorienting their attention, and nothing about their performance with pictorialarrow-cues indicates a visual attention impairment. However, they showed asubtle impairment in the right visual field when responding to an alphabetic cue,and a leftward–rightward shift of attention was required. Together, our resultsare compatible with recent findings from several different paradigms reporting thatattentional difficulties are most reliably observed among dyslexic participants whenthe stimulus materials are alphanumeric and strongly associated with phonologicalcodes (e.g. Hawelka et al., 2006; Ziegler et al., 2010). Performance on visualattention tasks that activate phonological codes may thus be constrained by theefficiency of phonological processing, which is so often impaired in dyslexia, aswas the case in the present study. However, a novel finding from our study was

72 J. Judge et al.


that the difficulty with alphanumeric cues was confined to one visual field; thus, wecannot rule out the possibility that their problem was related to difficulties inshifting attention in the direction of reading in response to letter cues. Futurestudies might focus on recording the specific parameters of eye movements suchas saccade size, direction and latency as this would allow comparisons betweenthe two reading groups on these important measures with respect to cueingbehaviour. Studies using different methodologies in which the perceptual spancan be assessed along with both exogenous and endogenous attention will alsobe needed to further this line of enquiry.

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Spatial Orienting of Attention in Dyslexic Adults using Directional and Alphabetic Cues