Auditory temporal processing and lexical/nonlexical reading in developmental dyslexics.

Relationships between lexical/nonlexical reading and auditory temporal processing were examined. Poor nonlexical readers (poor nonword readers, phonologic dyslexics) had difficulty across tone tasks irrespective of speed of presentation or mode of recall. Poor lexical readers (poor irregular word readers, surface dyslexics) had difficulty recalling tones in a sequence only when they were presented rapidly. Covariate analysis supported these findings, revealing that nonlexical (nonword) reading performance is associated with general auditory performance, but lexical (irregular word) reading is particularly associated with auditory sequencing. These findings suggest that phonologic and surface dyslexics perform differently on nonspeech auditory tasks. Because the two different types of poor readers did not differ significantly on tests of memory and learning but did differ on auditory tasks, we suggest that their performance on the auditory tasks may reflect auditory processing abnormalities as opposed to more general learning or memory difficulties. In addition to these observed qualitative differences between groups on the tone tasks, collapsing groups (all readers) revealed significant correlations between nonword reading and the Same-Different tone tasks in particular, whereas irregular word reading was not associated with any tone tasks; there also appears to be a quantitative relationship between nonlexical reading and Same-Different tone task performance as better or worse nonword reading predicts better or worse performance on the Same-Different tone tasks. In particular, it is conceivable that an auditory temporal processing deficit might contribute to poor nonword reading.