Phonological awareness and phoneme identification tasks were administered to dyslexic children and both chronological age (CA) and reading-level (RL) comparison groups. Dyslexic children showed less sharply defined categorical perception of a bath-path continuum varying voice onset time when compared to the CA but not the RL group. The dyslexic children were divided into two subgroups based on phoneme awareness. Dyslexies with low phonemic awareness made poorer /b/-/p/ distinctions than both CA and RL groups, but dyslexies with normal phonemic awareness did not. Examination of individual profiles revealed that the majority of subjects in each group exhibited normal categorical perception. However, 7 of 25 dyslexies had abnormal identification functions, compared to 1 subject in the CA group and 3 in the RL group. The results suggest that some dyslexic children have a perceptual deficit that may interfere with processing of phonological information. Speech perception difficulties may also be partially related to reading experience.
Bibliographical noteFunding Information:
Portions of the study were presented at the Society for Research in Child Development, New Orleans, 1993, and at the Society for the Scientific Study of Reading, San Francisco, 1995. This research was supported by NIMH Grants MH-47566 and MH-01188. We are grateful to Joanne Miller of Northeastern University for providing the bath–path stimuli. We thank the principals, teachers, and students of Landmark West School (Encino, CA), as well as Madrona, Magruder, and Casimir Middle Schools, and Arlington and Hickory Elementary Schools (Torrance, CA).