Duration perception for visual stimuli is impaired in dyslexia but deficits in visual processing may not be the culprits

Abstract

Dyslexics underperform controls in estimating and comparing time intervals defined by visual stimuli. Accuracy in vision-based duration perception requires efficient processing of visual events because these will define the onset and offset of time intervals. Since dyslexics have difficulties processing dimensions of visual stimuli like luminance contrasts and motion, we do not know the extent to which these visual deficits are responsible for their difficulties in judging time intervals. To address this gap, we asked adults with dyslexia and matched controls to perform an interval comparison task involving five different types of visual stimuli with different levels of challenge regarding luminance contrasts and motion. If the expected disadvantage of dyslexics in visual duration perception increased for stimuli requiring increased luminance or motion processing, this would indicate that visual processing plays a role. Results showed poorer time discrimination in dyslexics, but this disadvantage did not change according to stimulus type. Complementary analyses of oculomotor behavior during the task suggested that the poorer timing performance of dyslexics may relate instead to attention and/or engagement with the task. Our findings strengthen the evidence in favor of visual duration perception deficits in dyslexia, but not the hypothesis that these result from purely visual problems.

Domain-general but not speech-specific auditory duration perception predicts pseudoword reading in adults

“…Nevertheless, evidence was restricted to the dyslexic group, as we found after examining interactions ( Figure 4 ). Note that this analysis did not include speech-specific duration perception because extra data was obtained from a previous study of ours ( Catronas et al, 2023 ), in which only this modality of duration perception was assessed. The 26 + 24 participants from Catronas et al (2023) were already classified as controls vs. dyslexics, based on an extensive evaluation of reading profiles, and so we skipped the inspection of reading measures.…”

“…Note that this analysis did not include speech-specific duration perception because extra data was obtained from a previous study of ours ( Catronas et al, 2023 ), in which only this modality of duration perception was assessed. The 26 + 24 participants from Catronas et al (2023) were already classified as controls vs. dyslexics, based on an extensive evaluation of reading profiles, and so we skipped the inspection of reading measures. Descriptive values for these measures and the beeps task may be found in Supplementary Table SA1 from Supplementary materials.…”

“… Scatterplots for the relation between domain-general duration perception (Beeps) and the three dependent variables (reading measures) in the enlarged sample ( n = 96) considering different subgroups. Data from added controls ( n = 26) and added dyslexics ( n = 24) pertains to Catronas et al (2023) . Main sample refers to the current study ( n = 46).…”

“…Since our results were in line with the hypothesis that domain-general duration perception predicts the accuracy of pseudoword reading, we tested this association further with an enlarged sample to increase power and see whether evidence could be strengthened. This complementary analysis was conducted by adding data from participants in a previous study of ours ( Catronas et al, 2023 ). The goal of that study was to understand if impairments in visual time perception of dyslexics were secondary to visual problems or not.…”

“…To that end, we asked neurotypical adult readers to perform a behavioral interval-comparison task with beep sequences (domain-general duration perception), a pre-attentive VOT discrimination task with EEG recordings (speech-specific), and reading tasks relating to word decoding, pseudoword decoding and reading comprehension. Since our results pointed to an association between domain-general duration perception and pseudoword reading, we did a complementary analysis where we added data from another study of ours ( Catronas et al, 2023 ) to enlarge our sample, increase statistical power, and get more reliable results.…”