The "temporal processing deficit" hypothesis in dyslexia: New experimentalevidence

The notion that developmental dyslexia may result from a general, nonspecif ic, defect in perceiving rapidly changing auditory signals is a current sub ject of debate (so-called ''temporal processing deficit'' hypothesis). Thir teen phonological dyslexics (age 1013 years) and 10 controls matched for ch ronological and reading age were compared on a temporal order judgement (TO J) task using the succession of two consonants (/p/-/s/) within a cluster. Ln order to test the relevance of the temporal deficit hypothesis, the task also included two additional conditions where either the two stimuli were artificially slowed or the interstimulus interval was expanded. As expected , the TOJ performance was significantly poorer in dyslexics than in control s. Moreover, in the "slowed speech" condition dyslexics' performance improv ed to reach the normal controls' level, whereas no significant improvement occurred when increasing the interstimulus interval. Finally dyslexics' per formances, especially on the slowed condition, were found correlated with s everal tests of phonological processing (phoneme deletion, rhyme judgment, and nonword spelling tasks). These results lend support to the general temp oral deficit theory of dyslexia. (C) 2001 Academic Press.