Sensitivity to visual and auditory stimuli in children with developmental dyslexia

This study considered the extent to which 23 children with dyslexia differed from 23 reading age (RA) and 23 chronological age (CA) matched controls in their ability to make temporal judgements about auditory and visual sequences of stimuli, and in the speed of their reactions to the onsets and offsets of visual and auditory stimuli. The children with dyslexia were slower (p = 0.039) than the CA controls in their reactions to non-verbal auditory onsets (tones), were less able to recognize the first stimulus of a sequence of tones (p = 0.022), and were less accurate in identifying the initial phoneme of a sequence of three (p < 0.001). These characteristics may be manifestations of an impaired temporal processing system for rapid auditory stimuli. CA controls responded more quickly to tone onsets than to tone offsets (p = 0.025), but the dyslexic and RA groups showed no significant difference (p > 0.05) in their reaction times to onsets and offsets of these non-verbal auditory stimuli. Dyslexic readers showed impairment compared with CA controls in responding to the last of a sequence of three non-verbal visual stimuli (shapes), p = 0.02. Reaction times in the visual and auditory onset and offset tasks were richly intercorrelated in the control groups, but the dyslexic group did not show as many significant correlations in reaction times between the auditory and visual domains, or between the onset and offset RTs within each modality. These results suggest that there may be a less integrated cross-modal and intra-modal temporal system in children with dyslexia than in controls. In many of the measures in this study, the performance of the dyslexic group resembled that of the RA control group but differed from CA controls, which implies a developmental delay. The possibility that such a cognitive delay may be related to an underlying neurological disorder is discussed.