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For both adult and child readers of English, the first letter of a word plays an important role in lexical identification. Using the boundary paradigm during silent sentence reading, we examined whether the first-letter bias in parafoveal preprocessing is phonologically or orthographically driven and whether this differs between skilled adult and beginner child readers. Participants read sentences that contained either a correctly spelled word in preview (identity; e.g., "circus"), a preview letter string that maintained the phonology but manipulated the orthography of the first letter (P + O- preview; e.g., "sircus"), or a preview letter string that manipulated both the phonology and the orthography of the first letter (P- O- preview; e.g., "wircus"). There was a cost associated with manipulating the first letter of the target words in preview for both adults and children. Critically, during first-pass reading, both adult and child readers displayed similar reading times between P + O- and P- O- previews. This shows that the first-letter bias is driven by orthographic encoding and that the first letter's orthographic code in preview is crucial for efficient, early processing of phonology. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

We examined whether typical frequency effects observed in normal reading would also occur in a target search task using non-linguistic Landolt-C stimuli. In an initial learning session, we simulated development of frequency effects by controlling exposures participants received of Landolt-C clusters during learning. In a subsequent scanning session, we manipulated the cluster demarcation form of linear strings of Landolt-C clusters (i.e., spaced vs. unspaced vs. shaded unspaced). Participants were required to scan and search for pre-learnt target clusters that were embedded in longer Landolt-C strings. During learning, frequency effects were successfully simulated such that targets with more exposures received shorter fixation time than those with fewer exposures. Participants were unable to successfully detect the pre-learnt targets when they were embedded in the strings during scanning. No evidence of frequency effects was observed in the scanning session. In contrast, eye movement control was significantly influenced by cluster demarcation form, with increased difficulty for unspaced strings, less for shaded strings and least for spaced strings. Furthermore, typical landing position distributions that occur in reading of spaced languages also occurred during scanning of spaced Landolt-C strings but not for the shaded, nor the unspaced strings. In conclusion, exposure frequency effects were successfully simulated during learning but did not carry over to target search during scanning of Landolt-C strings. Possible reasons why frequency effects did not occur in the scanning session are discussed.

Wang et al. (Attention, Perception, and Psychophysics, in press, 2021) reported a Landolt-C learning and scanning experiment. In a learning session, they simulated exposure frequency effects successfully by training participants to learn target Landolt-C clusters with different exposures. The rate of learning high-frequency (HF) targets were greater than that of learning low-frequency (LF) targets. In a subsequent scanning session, participants were required to scan text-like Landolt-C strings to detect whether any pre-learnt target was embedded in the strings. The Landolt-C strings were displayed under different spacing formats (i.e., spaced format, unspaced format, and unspaced shaded format). However, the simulated exposure frequency effect did not occur in the scanning session. Wang et al. argued one straightforward reason for this might be because participants failed to maintain the memory of pre-learnt target to the scanning session. In the current study, we employed the same learning and scanning paradigm to investigate whether exposure frequency would occur in a target search task by using easier learning materials - pseudoword stimuli. The learning of pseudoword stimuli was much more successful than Landolt-C stimuli. Interestingly, however, we found a very different rate of learning effect such that the rate of learning LF targets was greater than HF targets. To our surprise, we did not find any influence of exposure frequency on eye movements during scanning even when participants were able to identify pre-learnt pseudowords in strings. Learning rate effect, exposure frequency effects, and saccadic targeting during the scanning of strings under different spacing formats are discussed in this paper.

We examined whether typical frequency effects observed in normal reading would also occur in a target search task using non-linguistic Landolt-C stimuli. In an initial learning session, we simulated development of frequency effects by controlling exposures participants received of Landolt-C clusters during learning. In a subsequent scanning session, we manipulated the cluster demarcation form of linear strings of Landolt-C clusters (i.e., spaced vs. unspaced vs. shaded unspaced). Participants were required to scan and search for pre-learnt target clusters that were embedded in longer Landolt-C strings. During learning, frequency effects were successfully simulated such that targets with more exposures received shorter fixation time than those with fewer exposures. Participants were unable to successfully detect the pre-learnt targets when they were embedded in the strings during scanning. No evidence of frequency effects was observed in the scanning session. In contrast, eye-movement control was significantly influenced by cluster demarcation form, with increased difficulty for unspaced strings, less for shaded strings, and least for spaced strings. Furthermore, typical landing position distributions that occur in reading of spaced languages also occurred during scanning of spaced Landolt-C strings but not for the shaded or the unspaced strings. In conclusion, exposure frequency effects were successfully simulated during learning but did not carry over to target search during scanning of Landolt-C strings. Possible reasons why frequency effects did not occur in the scanning session are discussed.

Although previous research has demonstrated that for adults external letters of words are more important than internal letters for lexical processing during reading, no comparable research has been conducted with children. This experiment explored, using the boundary paradigm during silent sentence reading, whether parafoveal pre-processing in English is more affected by the manipulation of external letters or internal letters, and whether this differs between skilled adult and beginner child readers. Six previews were generated: identity (e.g., monkey); external letter manipulations where either the beginning three letters of the word were substituted (e.g., rackey) or the last three letters of the word were substituted (e.g., monhig); internal letter manipulations; e.g., machey, mochiy); and an unrelated control condition (e.g., rachig). Results indicate that both adults and children undertook pre-processing of words in their entirety in the parafovea, and that the manipulation of external letters in preview was more harmful to participants’ parafoveal pre-processing than internal letters. The data also suggest developmental change in the time course of pre-processing, with children’s pre-processing delayed compared to that of adults. These results not only provide further evidence for the importance of external letters to parafoveal processing and lexical identification for adults, but also demonstrate that such findings can be extended to children.

During reading, binocular visual input results in superior performance and is particularly important in the pre-processing of parafoveal text prior to direct fixation. It is not yet clear whether binocular vision in the parafovea is necessary for accurate saccadic targeting, or for efficient pre-processing of upcoming text, prior to direct fixation. In the present sentence reading experiment, we used a dichoptic gaze-contingent moving window paradigm in order to establish 1) how much parafoveal binocular input is necessary for fluent reading and 2) which aspect of parafoveal processing is more reliant on binocular vision. Eye movement measures revealed that reading was disrupted unless word N + 1 was entirely binocular in the parafovea, though no additional benefit was observed when word N + 2 was also binocular. Additionally, while fixation durations and reading times were clearly affected by the manipulation, similarly pronounced changes in binocular saccadic parameters such as accuracy, speed, amplitude and velocity were not observed. We concluded that the disruption to reading caused by presenting monocular text to the right of fixation cannot be attributed to difficulties in targeting binocular saccacdes, but instead results from a decreased efficiency in the pre-processing of parafoveal text. These results provide further demonstration for the importance of binocular vision during written text processing.

We examined phonological recoding during silent sentence reading in teenagers with a history of dyslexia and their typically developing peers. Two experiments are reported in which participants' eye movements were recorded as they read sentences containing correctly spelled words (e.g., church), pseudohomophones (e.g., cherch), and spelling controls (e.g., charch). In Experiment 1 we examined foveal processing of the target word/nonword stimuli, and in Experiment 2 we examined parafoveal pre-processing. There were four participant groups-older teenagers with a history of dyslexia, older typically developing teenagers who were matched for age, younger typically developing teenagers who were matched for reading level, and younger teenagers with a history of dyslexia. All four participant groups showed a pseudohomophone advantage, both from foveal processing and parafoveal pre-processing, indicating that teenagers with a history of dyslexia engage in phonological recoding for lexical identification during silent sentence reading in a comparable manner to their typically developing peers.

Participants’ eye movements were measured as they read sentences in which individual letters within words were rotated. Both the consistency of direction and the magnitude of rotation were manipulated (letters rotated all in the same direction, or alternately clockwise and anti-clockwise, by 30° or 60°). Each sentence included a target word that was manipulated for frequency of occurrence. Our objectives were threefold: To quantify how change in the visual presentation of individual letters disrupted word identification, and whether disruption was consistent with systematic change in visual presentation; to determine whether inconsistent letter transformation caused more disruption than consistent letter transformation; and to determine whether such effects were comparable for words that were high and low frequency to explore the extent to which they were visually or linguistically mediated. We found that disruption to reading was greater as the magnitude of letter rotation increased, although even small rotations affected processing. The data also showed that alternating letter rotations were significantly more disruptive than consistent rotations; this result is consistent with models of lexical identification in which encoding occurs over units of more than one adjacent letter. These rotation manipulations also showed significant interactions with word frequency on the target word: Gaze durations and total fixation duration times increased disproportionately for low-frequency words when they were presented at more extreme rotations. These data provide a first step towards quantifying the relative contribution of the spatial relationships between individual letters to word recognition and eye movement control in reading.

Reading comes with a clear binocular advantage, expressed in shorter fixation times and fewer regressions in binocular relative to monocular visual presentations. Little is known, however, about whether the cost associated with monocular viewing derives primarily from the encoding of foveal information or in obtaining a preview benefit from upcoming parafoveal text. In the present sentence reading eye tracking experiment, the authors used a novel dichoptic binocular gaze-contingent moving window technique to selectively manipulate the amount of text made available to the reader both binocularly and monocularly in the fovea and parafovea on a fixation-by-fixation basis. This technique allowed the authors to quantify disruption to reading caused by prevention of binocular fusion during direct fixation of words and parafoveal preprocessing of upcoming text. Sentences were presented (a) binocularly; (b) monocularly; (c) with monocular text to the left of fixation; (d) with monocular text to the right of fixation; or (e) with all words other than the fixated word presented binocularly. A robust binocular advantage occurred for average fixation duration and regressions. Also, while there was a limited cost associated with monocular foveal processing, the restriction of parafoveal processing to monocular information was particularly disruptive. The findings demonstrate the critical importance of a unified binocular input for the efficient preprocessing text to the right of fixation. (PsycINFO Database Record

Children's eye movements were recorded to examine the role of word spacing and positional character frequency on the process of Chinese lexical acquisition during reading. Three types of two-character novel pseudowords were constructed: words containing characters in positions in which they frequently occurred (congruent), words containing characters in positions they do not frequently occur in (incongruent) and words containing characters that do not have a strong position bias (balanced). There were two phases within the experiment, a learning phase and a test phase. There were also two learning groups: half the children read sentences in a word-spaced format and the other half read the sentences in an unspaced format during the learning phase. All the participants read normal, unspaced text at test. A benefit of word spacing was observed in the learning phase, but not at test. Also, facilitatory effects of positional character congruency were found both in the learning and test phase; however, this benefit was greatly reduced at test. Furthermore, we did not find any interaction between word spacing and positional character frequencies, indicating that these two types of cues affect lexical acquisition independently. With respect to theoretical accounts of lexical acquisition, we argue that word spacing might facilitate the very earliest stages of word learning by clearly demarking word boundary locations. In contrast, we argue that characters' positional frequencies might affect relatively later stages of word learning

A great deal of eye-movement research has resulted in sophisticated computational models of skilled adult reading. As yet, insufficient eye-movement research has been conducted with children to allow a more thorough understanding of the developmental trajectory leading up to this end state. I argue that, in order to fully understand how children progress to skilled adult reading, it is necessary to consider changes in both cognitive processing and eye-movement behavior. By recording children’s eye movements during reading, researchers can document how printed text is encoded and incrementally delivered for subsequent cognitive processing, and understand how developmental changes in these two aspects of reading are interdependent.

We examined whether interword spacing would facilitate acquisition of new vocabulary for second language learners of Chinese. Participants' eye movements were measured as they read new vocabulary embedded in sentences during a learning session and a test session. In the learning session, participants read sentences in traditional unspaced format and half-read sentences with interword spacing. In the test session, all participants read unspaced sentences. Participants in the spaced learning group read the target words more quickly than those in the unspaced learning group. This benefit was maintained at test, indicating that the manipulation enhanced learning of the novel words and was not a transient effect limited to occasions when interword spacing was present in the printed text. The insertion of interword spaces may allow readers to form a more fully specified representation of the novel word, or to strengthen connections between representations of the constituent characters and the multi-character word.

We examined whether inserting spaces between words in Chinese text would help children learn to read new vocabulary. We recorded adults’ and 7- to 10-year-old children’s eye movements as they read new 2-character words, each embedded in four explanatory sentences (the learning session). Participants were divided into learning subgroups – half read word spaced sentences, and half read unspaced sentences. In the test session participants read the new words again, each in one new sentence; here, all participants read unspaced text. In the learning session, participants in the spaced group read the new words more quickly than participants in the unspaced group. Further, children in the spaced group maintained this benefit in the test session (unspaced text). In relation to three different models of Chinese lexical identification, we argue that the spacing manipulation allowed the children to form either stronger connections between the two characters’ representations and the corresponding, novel word representation, or to form a more fully specified representation of the word itself.

Purpose: We were particularly interested in whether binocular coordination when viewing stereoscopic images would be more comparable to when viewing a 2D representation, or when viewing a real stimulus array in depth. Methods: Data are reported from an experiment examining binocular coordination in response to stereoscopically presented stimuli. Movements of both eyes were recorded as participants viewed LED stimuli in a real scene with depth, a 2D image of the scene, and a stereoscopic image of the scene. Results: When viewing real LEDs, vergence during saccades re‐aligned the eyes in depth where necessary, with smaller adjustments during the following fixation. In contrast, when viewing the stereoscopic representation, vergence during saccades did not re‐align the eyes in depth. The only effect of target depth on vergence occurred during the following fixation. Conclusions: We conclude that disparity in parafoveal objects, in isolation from other depth cues (and, minimally, conflicting with blur), was insufficient for the visual system to target saccades appropriately in depth.

We examined the influence of a variety of visual factors on binocular coordination during saccadic orienting. Some experimental conditions placed similar demands on the oculomotor system as those that occur during reading, but in the absence of linguistic processing. We examined whether saccade target extent, preceding saccade magnitude, preceding saccade direction, and parafoveal availability of saccade target influenced fixation disparity. Disparities similar in magnitude and frequency to those obtained in previous binocular reading experiments occurred. Saccade magnitude had a robust influence upon fixation disparities. The results are very similar to those obtained in investigations of binocular coordination during reading, and indicate that similar patterns occur during reading-like eye scanning behaviour, in the absence of linguistic processing.

Two experiments were undertaken to examine whether there is an age-related change in the speed with which readers can capture visual information during fixations in reading. Children's and adults' eye movements were recorded as they read sentences that were presented either normally or as "disappearing text". The disappearing text manipulation had a surprisingly small effect on the children, inconsistent with the notion of an age-related change in the speed with which readers can capture visual information from the page. Instead, we suggest that differences between adults and children are related to the level of difficulty of the sentences for readers of different ages.

A study is reported in which eye movements were recorded when observers attempted to make a saccade to a target in the presence of a nearby and visually identical distractor. It was found that saccade targeting accuracy was completely unaffected by the presence of the distractor, except in the cases where the distractor was on the same axis as that of the saccadic movement. In this condition, some saccades landed between target and distractor, thus showing the global effect finding, known to occur when saccades are made to stimuli with sudden onset. The result demonstrates that a perceptual selection process, operating with higher resolution than that often associated with covert visual attention, can be used in the selection of saccadic targets.

The goal of this review is to evaluate the literature on binocular coordination during reading and non-reading tasks in adult, child, and dyslexic populations. The review begins with a description of the basic characteristics of eye movements during reading. Then, reading and non-reading studies investigating binocular coordination are evaluated. Areas of future research in the field are identified and discussed. Finally, some general conclusions are made regarding binocular coordination. The review demonstrates that findings from traditionally independent areas of research are largely consistent and complementary. Throughout the review, theoretical and methodological commonalities are identified and clarified in order to advance current understanding of this fundamental aspect of human visual processing.

Previous research has shown that prior exposure to a word’s substitution neighbor earlier in the same sentence can disrupt processing of that word, indicating that interword lexical priming occurs naturally during reading, due to the competition between lexical candidates during word identification. Through the present research, we extended these findings by investigating the effects of prior exposure to a word’s transposed-letter neighbor (TLN) earlier in a sentence. TLNs are constituted from the same letters, but in different orders. The findings revealed an inhibitory TLN effect, with longer total reading times for target words, and increased regressions to prime and target words, when the target followed a TLN rather than a control word. These findings indicate that prior exposure to a TLN can disrupt word identification during reading. We suggest that this is caused by a failure of word identification, due to the initial misidentification of the target word (potentially as its TLN) triggering postlexical checking.

Recent evidence indicates that each eye does not always fixate the same letter during reading and there has been some suggestion that processing difficulty may influence binocular coordination. We recorded binocular eye movements from children and adults reading sentences containing a word frequency manipulation. We found disparities of significant magnitude between the two eyes for all participants, with greater disparity magnitudes in children than adults. All participants made fewer crossed than uncrossed fixations. However, children made a higher proportion of crossed fixations than adults. We found no influence of word frequency on children’s fixations and on binocular coordination in adults.

There has been considerable variability within the literature concerning the extent to which deaf/hard of hearing individuals are able to process phonological codes during reading. Two experiments are reported in which participants’ eye movements were recorded as they read sentences containing correctly spelled words (e.g., church), pseudohomophones (e.g., cherch), and spelling controls (e.g., charch). We examined both foveal processing and parafoveal pre‐processing of phonology for three participant groups—teenagers with permanent childhood hearing loss (PCHL), chronological age‐matched controls, and reading age‐matched controls. The teenagers with PCHL showed a pseudohomophone advantage from both directly fixated words and parafoveal preview, similar to their hearing peers. These data provide strong evidence for phonological recoding during silent reading in teenagers with PCHL.

Humans typically make use of both eyes during reading, which necessitates precise binocular coordination in order to achieve a unified perceptual representation of written text. A number of studies have explored the magnitude and effects of naturally occurring and induced horizontal fixation disparity during reading and non-reading tasks. However, the literature concerning the processing of disparities in different dimensions, particularly in the context of reading, is considerably limited. We therefore investigated vertical vergence in response to stereoscopically presented linguistic stimuli with varying levels of vertical offset. A lexical decision task was used to explore the ability of participants to fuse binocular image disparity in the vertical direction during word identification. Additionally, a lexical frequency manipulation explored the potential interplay between visual fusion processes and linguistic processes. Results indicated that no significant motor fusional responses were made in the vertical dimension (all p-values > .11), though that did not hinder successful lexical identification. In contrast, horizontal vergence movements were consistently observed on all fixations in the absence of a horizontal disparity manipulation. These findings add to the growing understanding of binocularity and its role in written language processing, and fit neatly with previous literature regarding binocular coordination in non-reading tasks.

In this experiment, the extent to which beginning readers process phonology during lexical identification in silent sentence reading was investigated. The eye movements of children aged seven to nine years and adults were recorded as they read sentences containing either a correctly spelled target word (e.g., girl), a pseudohomophone (e.g., gerl), or a spelling control (e.g., garl). Both children and adults showed a benefit from the valid phonology of the pseudohomophone, compared to the spelling control during reading. This indicates that children as young as seven years old exhibit relatively skilled phonological processing during reading, despite having moved past the use of overt phonological decoding strategies. In addition, in comparison to adults, children’s lexical processing was more disrupted by the presence of spelling errors, suggesting a developmental change in the relative dependence upon phonological and orthographic processing in lexical identification during silent sentence reading.

Two experiments were conducted to investigate the flexibility of letter-position encoding in word identification during reading. In both experiments, two tasks were used. First, participants’ eye movements were measured as they read sentences containing transposed letter (TL) strings. Second, participants were presented with the TL strings in isolation and were asked to discriminate them from nonwords. In Experiment 1, we manipulated the distance between transposed letters (ligament vs. liagment vs. limagent vs. lieamgnt). Reading/response times increased with the distance between TLs. In Experiment 2, we manipulated whether the TLs were consonants, vowels, or one of each (ssytem vs. faeture vs. fromat). Reading/response times showed that CV transpositions were the most disruptive. In both experiments, response accuracy was particularly poor for words presented in isolation when there was an intervening letter between TLs. These data show that processing across multiple fixations, and the presence of a meaningful sentence context, are important for flexible letter position encoding in lexical identification.

Previous studies examining binocular coordination during reading have reported conflicting results in terms of the nature of disparity (e.g. Kliegl, Nuthmann, & Engbert (Journal of Experimental Psychology General 135:12-35, 2006); Liversedge, White, Findlay, & Rayner (Vision Research 46:2363-2374, 2006). One potential cause of this inconsistency is differences in acquisition devices and associated analysis technologies. We tested this by directly comparing binocular eye movement recordings made using SR Research EyeLink 1000 and the Fourward Technologies Inc. DPI binocular eye-tracking systems. Participants read sentences or scanned horizontal rows of dot strings; for each participant, half the data were recorded with the EyeLink, and the other half with the DPIs. The viewing conditions in both testing laboratories were set to be very similar. Monocular calibrations were used. The majority of fixations recorded using either system were aligned, although data from the EyeLink system showed greater disparity magnitudes. Critically, for unaligned fixations, the data from both systems showed a majority of uncrossed fixations. These results suggest that variability in previous reports of binocular fixation alignment is attributable to the specific viewing conditions associated with a particular experiment (variables such as luminance and viewing distance), rather than acquisition and analysis software and hardware.

Compared to skilled adult readers, children typically make more fixations that are longer in duration, shorter saccades, and more regressions, thus reading more slowly (Blythe and Joseph, 2011). Recent attempts to understand the reasons for these differences have discovered some similarities (e.g., children and adults target their saccades similarly; Joseph, Liversedge, Blythe, White, and Rayner, 2009) and some differences (e.g., children's fixation durations are more affected by lexical variables; Blythe, Liversedge, Joseph, White, and Rayner, 2009) that have yet to be explained. In this article, the E-Z Reader model of eye-movement control in reading (Reichle, 2011; Reichle, Pollatsek, Fisher, and Rayner, 1998) is used to simulate various eye-movement phenomena in adults vs. children in order to evaluate hypotheses about the concurrent development of reading skill and eye-movement behavior. These simulations suggest that the primary difference between children and adults is their rate of lexical processing, and that different rates of (post-lexical) language processing may also contribute to some phenomena (e.g., children's slower detection of semantic anomalies; Joseph et al., 2008). The theoretical implications of this hypothesis are discussed, including possible alternative accounts of these developmental changes, how reading skill and eye movements change across the entire lifespan (e.g., college-aged vs. older readers), and individual differences in reading ability. © 2013 Elsevier Inc. All rights reserved.

In this commentary we concur with Frost's view of the centrality of universal principles in models of word identification. However, we argue that other processes in sentence comprehension also fundamentally constrain the nature of written word identification. Furthermore, these processes appear to be universal. We, therefore, argue that universality in word identification should not be considered in isolation, but instead in the context of other linguistic processes that occur during normal reading.

We were particularly interested in whether binocular coordination when viewing stereoscopic images would be more comparable to when viewing a 2D representation, or when viewing a real stimulus array in depth.Data are reported from an experiment examining binocular coordination in response to stereoscopically presented stimuli. Movements of both eyes were recorded as participants viewed LED stimuli in a real scene with depth, a 2D image of the scene, and a stereoscopic image of the scene.When viewing real LEDs, vergence during saccades re-aligned the eyes in depth where necessary, with smaller adjustments during the following fixation. In contrast, when viewing the stereoscopic representation, vergence during saccades did not re-align the eyes in depth. The only effect of target depth on vergence occurred during the following fixation.We conclude that disparity in parafoveal objects, in isolation from other depth cues (and, minimally, conflicting with blur), was insufficient for the visual system to target saccades appropriately in depth.

Children with developmental dyslexia show reading impairment compared to their peers, despite being matched on IQ, socio-economic background, and educational opportunities. The neurological and cognitive basis of dyslexia remains a highly debated topic. Proponents of the magnocellular theory, which postulates abnormalities in the M-stream of the visual pathway cause developmental dyslexia, claim that children with dyslexia have deficient binocular coordination, and this is the underlying cause of developmental dyslexia. We measured binocular coordination during reading and a non-linguistic scanning task in three participant groups: adults, typically developing children, and children with dyslexia. A significant increase in fixation disparity was observed for dyslexic children solely when reading. Our study casts serious doubts on the claims of the magnocellular theory. The exclusivity of increased fixation disparity in dyslexics during reading might be a result of the allocation of inadequate attentional and/or cognitive resources to the reading process, or suboptimal linguistic processing per se. © 2011 Kirkby et al.

Children’s eye movements during reading. In this chapter, we evaluate the literature on children’s eye movements during reading to date. We describe the basic, developmental changes that occur in eye movement behaviour during reading, discuss age-related changes in the extent and time course of information extraction during fixations in reading, and compare the effects of visual and linguistic manipulations in the text on children’s eye movement behaviour in relation to skilled adult readers. We argue that future research will benefit from examining how eye movement behaviour during reading develops in relation to language and literacy skills, and use of computational modelling with children’s eye movement data may improve our understanding of the mechanisms that underlie the progression from beginning to skilled reader.

We investigated the effective fusional range for written stimuli in children and adults in a natural viewing situation. We recorded binocular eye movements in children and adults during processing of stereoscopically presented words in a lexical decision task. The effect of disparity magnitude on ease of fusion caused decreased response accuracy, increasing numbers of fixations and increased trial viewing times when retinal disparity exceeded one character space. The data suggest that retinal inputs of a word that are disparate by up to one character (0.37°) fall within the effective fusional range such that lexical decisions are not impaired.

The present study examined the effects of word length on children’s eye movement behaviour when other variables were carefully controlled. Importantly, the results showed that word length influenced children’s reading times and fixation positions on words. Furthermore, children exhibited stronger word length effects than adults in gaze durations and refixations. Adults and children generally did not differ in initial landing positions, but did differ in refixation behaviour. Overall, the results indicated that while adults and children show similar effects of word length for early measures of eye movement behaviour, differences emerge in later measures.

Humans actively explore their visual environment by moving their eyes. Precise coordination of the eyes during visual scanning underlies the experience of a unified perceptual representation and is important for the perception of depth. We report data from three psychological experiments investigating human binocular coordination during visual processing of stereoscopic stimuli.In the first experiment participants were required to read sentences that contained a stereoscopically presented target word. Half of the word was presented exclusively to one eye and half exclusively to the other eye. Eye movements were recorded and showed that saccadic targeting was uninfluenced by the stereoscopic presentation, strongly suggesting that complementary retinal stimuli are perceived as a single, unified input prior to saccade initiation. In a second eye movement experiment we presented words stereoscopically to measure Panum's Fusional Area for linguistic stimuli. In the final experiment we compared binocular coordination during saccades between simple dot stimuli under 2D, stereoscopic 3D and real 3D viewing conditions. Results showed that depth appropriate vergence movements were made during saccades and fixations to real 3D stimuli, but only during fixations on stereoscopic 3D stimuli. 2D stimuli did not induce depth vergence movements. Together, these experiments indicate that stereoscopic visual stimuli are fused when they fall within Panum's Fusional Area, and that saccade metrics are computed on the basis of a unified percept. Also, there is sensitivity to non-foveal retinal disparity in real 3D stimuli, but not in stereoscopic 3D stimuli, and the system responsible for binocular coordination responds to this during saccades as well as fixations.

The present study employs a stereoscopic manipulation to present sentences in three dimensions to subjects as they read for comprehension. Subjects read sentences with (a) no depth cues, (b) a monocular depth cue that implied the sentence loomed out of the screen (i.e., increasing retinal size), (c) congruent monocular and binocular (retinal disparity) depth cues (i.e., both implied the sentence loomed out of the screen) and (d) incongruent monocular and binocular depth cues (i.e., the monocular cue implied the sentence loomed out of the screen and the binocular cue implied it receded behind the screen). Reading efficiency was mostly unaffected, suggesting that reading in three dimensions is similar to reading in two dimensions. Importantly, fixation disparity was driven by retinal disparity; fixations were significantly more crossed as readers progressed through the sentence in the congruent condition and significantly more uncrossed in the incongruent condition. We conclude that disparity depth cues are used on-line to drive binocular coordination during reading.

Summary Reading, an essential skill for successful function in today's society, is a complex psychological process involving vision, memory, and language comprehension [1, 2]. Variability in fixation durations during reading reflects the ease of text comprehension [3–5], and increased word frequency results in reduced fixation times [6–8]. Critically, readers not only process the fixated foveal word but also preprocess the parafoveal word to its right, thereby facilitating subsequent foveal processing. Typically, text is presented binocularly, and the oculomotor control system precisely coordinates the two frontally positioned eyes online [7, 9–13]. Binocular, compared to monocular, visual processing typically leads to superior performance [10, 13–15], termed the "binocular advantage"; few studies have investigated the binocular advantage in reading [16–18]. We used saccade-contingent display change methodology [19] to demonstrate the benefit of binocular relative to monocular text presentation for both parafoveal and foveal lexical processing during reading. Our results demonstrate that denial of a unified visual signal derived from binocular inputs provides a cost to the efficiency of reading, particularly in relation to high-frequency words. Our findings fit neatly with current computational models of eye movement control during reading, wherein successful word identification is a primary determinant of saccade initiation.