ASA 125th Meeting Ottawa 1993 May

3aSP15. Reading disability: A deficit in rate of auditory processing or in phonetic coding?

Maria Mody

Michael Studdert-Kennedy

Haskins Labs., 270 Crown St., New Haven, CT 06511

The study investigates a general hypothesis regarding the bases of certain reading disabilities: poor readers suffer from an impaired rate of auditory processing [P. Tallal, Brain Lang. 9, 182--198 (1980)], such that they are unable to discriminate or detect the order of a pair of brief complex tones at short interstimulus intervals. Such children also had difficulty with two synthetic speech sounds, /ba/ and /da/, on analogous tasks, which was similarly attributed to a deficit in the processing of rapid acoustic changes, such as those which occur in formant transitions signaling place of articulation in stop consonants. The present study, in establishing the significantly lower performance by poor readers, compared to good readers, with /ba/ and /da/, at short interstimulus intervals (100, 50, and 10 ms), however, failed to show any significant difference between the groups when the acoustic-phonetic contrast of the stimulus pair to be discriminated was increased, as with /ba/--/sa/ or /da/--/(sh)a/. Further, that the good and poor readers here, did not differ significantly on discrimination at these short interstimulus intervals, with acoustically similar nonspeech sinewave analogs of /ba/ and /da/, appears to implicate the role of phonetic processing.