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Whether eye-movements deficits are causal in reading disorders (RD) or rather a consequence of linguistic processing difficulty experienced by disabled readers has been extensively debated.Since RD are frequently comorbid with the Neurofibromatosis type1 (NF1), children with NF1 were used as a comparison group for children with dyslexia in this study.Eye movements were recorded while 21 dyslexic, 20 NF1, and 20 typically developing children performed an oculomotor lateralized bisection task. In this experiment, we manipulated the type of stimulus - discrete (words and strings of hashes) versus continuous (solid lines) - and the visual field where the stimulus was displayed (left vs right). The results showed that (1) only proficient readers (TD and NF1 without RD) showed fully developed oculomotor mechanisms for efficient reading, with a clear preferred viewing location located to the left of the word's centre in both visual fields, and fine-tuned saccade targeting guided by the between-character space information and (2) NF1 poor readers mirrored the dyslexic eye movement behaviour, with less accuracy and more variability in saccadic programming, no sensitivity to the discreteness of the stimuli, particularly in the left visual field. We concluded that disruption to oculomotor behaviour reflectsthe fact that many of the processes involved in reading are not yet automatized for children with RD, independently of NF1. This suggests that the differences in saccade targeting strategy between children with and without RD would be secondary consequences of their reduced reading experience., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The present study investigated the impact of inter-character spacing on saccade programming in beginning readers and dyslexic children. In two experiments, eye movements were recorded while dyslexic children, reading-age, and chronological-age controls, performed an oculomotor lateralized bisection task on words and strings of hashes presented either with default inter-character spacing or with extra spacing between the characters. The results of Experiment 1 showed that (1) only proficient readers had already developed highly automatized procedures for programming both left- and rightward saccades, depending on the discreteness of the stimuli and (2) children of all groups were disrupted (i.e., had trouble to land close to the beginning of the stimuli) by extra spacing between the characters of the stimuli, and particularly for stimuli presented in the left visual field. Experiment 2 was designed to disentangle the role of inter-character spacing and spatial width. Stimuli were made the same physical length in the default and extra-spacing conditions by having more characters in the default spacing condition. Our results showed that inter-letter spacing still influenced saccade programming when controlling for spatial width, thus confirming the detrimental effect of extra spacing for saccade programming. We conclude that the beneficial effect of increased inter-letter spacing on reading can be better explained in terms of decreased visual crowding than improved saccade targeting.

Two eye-movement experiments were conducted to examine the effects of font type on the recognition of words presented in central vision, using a variable-viewing-position technique. Two main questions were addressed: (1) Is the optimal viewing position (OVP) for word recognition modulated by font type? (2) Is the cursive font more appropriate than the printed font in word recognition in children who exclusively write using a cursive script? In order to disentangle the role of perceptual difficulty associated with the cursive font and the impact of writing habits, we tested French adults (Experiment 1) and second-grade French children, the latter having exclusively learned to write in cursive (Experiment 2). Results revealed that the printed font is more appropriate than the cursive for recognizing words in both adults and children: adults were slightly less accurate in cursive than in printed stimuli recognition and children were slower to identify cursive stimuli than printed stimuli. Eye-movement measures also revealed that the OVP curves were flattened in cursive font in both adults and children. We concluded that the perceptual difficulty of the cursive font degrades word recognition by impacting the OVP stability., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The double-drift stimulus (a drifting Gabor with orthogonal internal motion) generates a large discrepancy between its physical and perceived path. Surprisingly, saccades directed to the double-drift stimulus land along the physical, and not perceived, path (Lisi M, Cavanagh P. Curr Biol 25: 2535-2540, 2015). We asked whether memory-guided saccades exhibited the same dissociation from perception. Participants were asked to keep their gaze centered on a fixation dot while the double-drift stimulus moved back and forth on a linear path in the periphery. The offset of the fixation was the go signal to make a saccade to the target. In the visually guided saccade condition, the Gabor kept moving on its trajectory after the go signal but was removed once the saccade began. In the memory conditions, the Gabor disappeared before or at the same time as the go-signal (0- to 1,000-ms delay) and participants made a saccade to its remembered location. The results showed that visually guided saccades again targeted the physical rather than the perceived location. However, memory saccades, even with 0-ms delay, had landing positions shifted toward the perceived location. Our result shows that memory- and visually guided saccades are based on different spatial information. NEW & NOTEWORTHY We compared the effect of a perceptual illusion on two types of saccades, visually guided vs. memory-guided saccades, and found that whereas visually guided saccades were almost unaffected by the perceptual illusion, memory-guided saccades exhibited a strong effect of the illusion. Our result is the first evidence in the literature to show that visually and memory-guided saccades use different spatial representations.

It is well known that the metrical properties of saccadic eye movements are strongly influenced by the extraction of low-level visual features (e.g., luminance). Higher-level visual features (e.g., contour) also play a role, but their relative contribution and time course remain undetermined. Here, we investigated this issue, by testing the influence of contour on saccade metrics. We used a saccade-targeting task in which a peripheral target was, on some trials, simultaneously displayed with a less eccentric distractor. This paradigm is known to yield a global effect, that is a deviation of the eyes towards an intermediate location between the stimuli. The novelty was to test whether this effect would vary with the alignment of the distractor's elementary features. Distractors were of high vs. low luminance, and composed of 16 pixels that were either aligned or misaligned by 0.23° or 0.43°. Our prediction, under the hypothesis that contour intervenes, was that aligned distractors, which formed a definite contour, would deviate the eyes more strongly than misaligned distractors. On the contrary, we found that distractors of high luminance produced greater eye deviations when they were misaligned, and hence more largely spread, than when they were aligned. Furthermore, low-luminance distractors deviated the eyes to the same extent irrespective of their alignment, though showing a reversed, contour-like, effect of alignment for early-triggered saccades. We proposed that contour has only limited influence on saccade metrics, when other, lower-level and more salient visual features, such as the extent of the stimulus pattern, are available., (Copyright © 2014 Elsevier Ltd. All rights reserved.)