Lipread-induced phonetic recalibration in dyslexia

Auditory phoneme categories are less well-defined in developmental dyslexic readers than in fluent readers. Here, we examined whether poor recalibration of phonetic boundaries might be associated with this deficit. 22 adult dyslexic readers were compared with 22 fluent readers on a phoneme identification task and a task that measured phonetic recalibration by lipread speech (Bertelson, Vroomen, & De Gelder, 2003). In line with previous reports, we found that dyslexics were less categorical in the labeling of the speech sounds. The size of their phonetic recalibration effect, though, was comparable to that of normal readers. This result indicates that phonetic recalibration is unaffected in dyslexic readers, and that it is unlikely to lie at the foundation of their auditory phoneme categorization impairments. For normal readers however, it appeared that a well-calibrated system is related to auditory precision as the steepness of the auditory identification curve positively correlated with recalibration.