Selective Impairment Of Covert Attention In Chinese Dyslexic Children

Developmental dyslexia are important contemporary research issues in developmental psychology. A large number of empirical studies have explored the cause(s) of this developmental disorder and several theories have been proposed in the literature. Several recent studies have suggested deficits in spatial attention in children with developmental dyslexia, and a longitudinal study even showed that deficits in spatial visual attention may be a causal factor for developmental dyslexia. The shift of gaze and that of covert attention are overlapping during reading. A number of studies have demonstrated that dyslexic children have deficits in covert attentional orienting. However, it remains unclear if dyslexics also have deficits in overt attentional orienting, as manifested in eye movements. The present study adopted a cueing task and a free search task to explore if lliere are both covert and overt attentional deficits in developmental dyslexia by examining inhibition of return (IOR), a crucial mechanism of attentional orienting. Robust IOR effect was observed in both tasks in typically developing age-matched children, and in children with reading abilities that matched to the dyslexic children. Dyslexic children, however, showed impaired IOR in the covert attentional task (cueing) but not in the overt attentional task (visual search). These results suggest that covert attentional orienting is selectively impaired in dyslexic children and this deficit may be the significant contributor to developmental dyslexia. In a second year follow-up, the present study examined the phonological awareness of these three groups of children, at both phoneme and syllable levels. We did not find any phonological awareness deficits in the dyslexic children. This important finding suggests that the covert attentional deficits does not have any impact on phonological awareness; the contribution of attentional deficits to dyslexia is not mediated by phonological processes.