Visual Attention Span Deficits in Developmental Dyslexia: A Meta-analysis

Abstract

Background: Visual attention span (VAS) refers to the number of visual elements processed simultaneously in a multielement array. Yet, whether VAS deficits are markers of developmental dyslexia (DD) have not been systematically explored.Aim: The present meta-analysis aimed to investigate the relation between VAS deficits and dyslexia.Methods: A meta-analysis based on 31 articles, 53 independent studies, and 4149 subjects was conducted. Effect sizes for each study were calculated and a random-effect model was selected. Task and stimulus types in the VAS task, writing system, orthographic depth, control group type and age were included as possible moderators. Results: 1) VAS in dyslexic individuals was significantly worse than typically developing individuals, 2) task-stimulus type (report-verbal/n-back-verbal/n-back-non-verbal), writing system (alphabetic vs. Chinese) and control group type (age match vs. reading match) had significant moderating effects. That is, VAS deficits were more severe in verbal stimuli based on report task than in verbal and nonverbal stimuli based on n-back task, VAS deficits were more severe in alphabetic language than in Chinese and VAS deficits were more severe when compared with age matched controls than compared with reading matched controls. Conclusion: VAS deficits may be possible etiologies for DD and moderated by task-stimulus type, writing system and control group type. Implications of these findings regarding the understanding of dyslexia were discussed.