Do dyslexic individuals present a reduced visual attention span? Evidence from visual recognition tasks of non-verbal multi-character arrays.

A controversy has recently developed regarding the hypothesis that developmental dyslexia may be caused, in some cases, by a reduced visual attention span (VAS). To examine this hypothesis, independent of phonological abilities, researchers tested the ability of dyslexic participants to recognize arrays of unfamiliar visual characters. Employing this test, findings were rather equivocal: dyslexic participants exhibited poor performance in some studies but normal performance in others. The present study explored four methodological differences revealed between the two sets of studies that might underlie their conflicting results. Specifically, in two experiments we examined whether a VAS deficit is (a) specific to recognition of multi-character arrays as wholes rather than of individual characters within arrays, (b) specific to characters' position within arrays rather than to characters' identity, or revealed only under a higher attention load due to (c) low-discriminable characters, and/or (d) characters' short exposure. Furthermore, in this study we examined whether pure dyslexic participants who do not have attention disorder exhibit a reduced VAS. Although comorbidity of dyslexia and attention disorder is common and the ability to sustain attention for a long time plays a major rule in the visual recognition task, the presence of attention disorder was neither evaluated nor ruled out in previous studies. Findings did not reveal any differences between the performance of dyslexic and control participants on eight versions of the visual recognition task. These findings suggest that pure dyslexic individuals do not present a reduced visual attention span.