Hazel I. Blythe

Binocular coordination during reading and non-reading tasks

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.

The binocular coordination of eye movements during reading in children and adults

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 childrens fixations and on binocular coordination in adults.

Word length and landing position effects during reading in children and adults

The present study examined the effects of word length on childrens eye movement behaviour when other variables were carefully controlled. Importantly, the results showed that word length influenced childrens 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.

Children's and adults' processing of anomaly and implausibility during reading : Evidence from eye movements

The eye movements of 24 children and 24 adults were monitored to compare how they read sentences containing plausible, implausible, and anomalous thematic relations. In the implausible condition the incongruity occurred due to the incompatibility of two objects involved in the event denoted by the main verb. In the anomalous condition the direct object of the verb was not a possible verb argument. Adults exhibited immediate disruption with the anomalous sentences as compared to the implausible sentences as indexed by longer gaze durations on the target word. Children exhibited the same pattern of effects as adults as far as the anomalous sentences were concerned, but exhibited delayed effects of implausibility. These data indicate that while children and adults are alike in their basic thematic assignment processes during reading, children may be delayed in the efficiency with which they are able to integrate pragmatic and real-world knowledge into their discourse representation.

Reading Text Increases Binocular Disparity in Dyslexic Children

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.

Saccade target selection: Do distractors affect saccade accuracy?

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 impact of universal newborn hearing screening on long-term literacy outcomes: a prospective cohort study

Objective To determine whether the benefits of universal newborn hearing screening (UNHS) seen at age 8 years persist through the second decade. Design Prospective cohort study of a population sample of children with permanent childhood hearing impairment (PCHI) followed up for 17 years since birth in periods with (or without) UNHS. Setting Birth cohort of 100 000 in southern England. Participants 114 teenagers aged 13–19 years, 76 with PCHI and 38 with normal hearing. All had previously their reading assessed aged 6–10 years. Interventions Birth in periods with and without UNHS; confirmation of PCHI before and after age 9 months. Main outcome measure Reading comprehension ability. Regression modelling took account of severity of hearing loss, non-verbal ability, maternal education and main language. Results Confirmation of PCHI by age 9 months was associated with significantly higher mean z-scores for reading comprehension (adjusted mean difference 1.17, 95% CI 0.36 to 1.97) although birth during periods with UNHS was not (adjusted mean difference 0.15, 95% CI −0.75 to 1.06). The gap between the reading comprehension z-scores of teenagers with early compared with late confirmed PCHI had widened at an adjusted mean rate of 0.06 per year (95% CI −0.02 to 0.13) during the 9.2-year mean interval since the previous assessment. Conclusions The benefit to reading comprehension of confirmation of PCHI by age 9 months increases during the teenage years. This strengthens the case for UNHS programmes that lead to early confirmation of permanent hearing loss. Trial registration number ISRCTN03307358.

Lexical and Sublexical Influences on Eye Movements During Reading

In this paper, we briefly review some recent studies that have clearly demonstrated in importance of lexical factors on eye movements during reading. We introduce the reader to eye-movement recording and explain its importance within the field of experimental psychology as a tool with which we can examine the psychological processes underlying reading. We then provide a summary of (mainly) eye-movement experiments in three areas: reading disappearing text, reading text with transposed letters, and morphological processing of compound words. Throughout the paper our central claim is that processes associated with lexical identification exert a strong and quite immediate effect on eye-movement behaviour during reading.

Investigating eye movement acquisition and analysis technologies as a causal factor in differential prevalence of crossed and uncrossed fixation disparity during reading and dot scanning

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.

Binocular coordination during scanning of simple dot stimuli

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.