Abstract:
Psychoacoustic studies cast some doubt on the hypothesis that deficits in auditory temporal processing cause speech and language disorders. First, the temporal acuity of the auditory system so greatly exceeds that required by tasks considered to support this hypothesis [e.g., Tallal and Piercy, Nature 241, 468--469 (1973)] that disordered subjects would be quite unable to understand speech if their basic temporal processing were as imprecise as it is proposed to be. Second, in a study of 127 normal-hearing listeners, nonsense-syllable recognition was not correlated with temporal discrimination measured with various nonspeech stimuli, and the same result was later obtained for sentences, words and CV's, although all speech measures load on a common factor. Third, structural-equation models were fitted to data collected from 24 college students with specific reading disabilities, and 70 who were ``normal.'' Data to be predicted included passage comprehension, word-attack skills, and word identification. A model using measures of speech perception and of intelligence yielded 0.7>r[sup 2]>0.9, but these predictions were not improved by nonspeech measures of auditory temporal processing. A viable hypothesis is that sensory processing speed may be only indirectly related to some speech-language disabilities, but more directly related to intelligence. [Work supported by NIH/NIDCD.]