Lateralized temporal order judgement in dyslexia

Temporal and spatial attentional deficits in dyslexia were investigated using a lateralized visual temporal order judgment (TOJ) paradigm that allowed both sensitivity to temporal order and spatial attentional bias to be measured. Findings indicate that adult participants with a positive screen for dyslexia were significantly less sensitive to the temporal order of the stimuli than control participants, but did not show a significantly different lateral bias. However, the data indicated that performance on the TOJ task dissociated into at least three factors. One loaded on trials with long Stimulus Onset Asynchronies (SOA) and was strongly correlated with full-scale IQ (FSIQ), and, while also correlated with both poor reading and with symptoms of attentional deficit disorder, was not specific to these. The second factor loaded on trials with short SOAs in which the left stimulus was presented first. Low scores on this factor were associated with poor non-word reading accuracy, and factor scores accounted for variance in non-word reading accuracy that was not accounted for by either FSIQ or the presence of a phonological deficit. This suggests that a “left mini-neglect” syndrome, also reported in attention deficit and hyperactivity disorder, may directly contribute to poor non-word reading. However, attentional deficit symptoms loaded not only on this factor, but also on a third factor, representing on trials at short SOAs in which the first stimulus was presented in left hemifield. This suggests that attentional deficit symptoms impaired temporal processing at short SOAs, regardless of the hemifield in with the stimuli were presented. We conclude that people with attentional deficits find a visual TOJ task difficult when the stimuli are presented rapidly, regardless of FSIQ, and that where a rightward attentional bias is present, non-word reading accuracy may be directly impaired, even in the absence of a phonological deficit.