Evidence for impaired visuoperceptual organisation in developmental dyslexics and its relation to temporal processes.

An analysis of normal and dyslexic readers' reaction-time (RT) performance in a standard visualdetection task (Experiment A) and in temporally primed visual detection (Experiment B) reveals a tendency for significantly longer search and detection RTs for dyslexic relative to the performance of normal readers. Consistent with previous studies, the RTs of normal readers and fast dyslexic responders exhibited target-specific priming effects. In contrast, in addition to increased but statistically insignificant target priming, a set of slower dyslexic responders showed strong negative priming on target-absent trials. In spite of the longer detection latencies produced by these dyslexic participants, no evidence was found to suggest that negative priming occurred as a general function of increasing difficulty in task performance (Experiment C). The enhanced positive and the negative priming effects are both interpreted in the context of the possible deployment of attentional mechanisms to the priming stimulus. The extent to which this strategy is characteristic of dyslexic performance as a whole may relate to the degree to which the dyslexic responder concerned experiences some general temporal processing impairment: Attentional deployment in this instance serving to compensate a lack of the requisite temporal resolution required for coding the spatiotemporal structure of the prime.