Exploring dyslexics' phonological deficit I: lexical vs sub-lexical and input vs output processes.

We report a series of experiments designed to explore the locus of the phonological deficit in dyslexia. Phonological processing of dyslexic adults is compared to that of age- and IQ-matched controls. Dyslexics' impaired performance on tasks involving nonwords suggests that sub-lexical phonological representations are deficient. Contrasting nonword repetition vs auditory nonword discrimination suggests that dyslexics are specifically impaired in input phonological processing. These data are compatible with the hypothesis that the deficit initially affects input sub-lexical processes, and further spreads to output and lexical processes in the course of language acquisition. Further longitudinal research is required to confirm this scenario as well as to tease apart the role of the quality of phonological representations from that of verbal short-term memory processes.