Perceptual learning of acoustic noise by individuals with dyslexia.

PURPOSE: A phonological deficit is thought to affect most individuals with developmental dyslexia. The present study addresses whether the phonological deficit is caused by difficulties with perceptual learning of fine acoustic details.

METHOD: A demanding test of nonverbal auditory memory, "noise learning," was administered to both adults with dyslexia and control adult participants. On each trial, listeners had to decide whether a stimulus was a 1-s noise token or 2 abutting presentations of the same 0.5-s noise token (repeated noise). Without the listener's knowledge, the exact same noise tokens were presented over many trials. An improved ability to perform the task for such "reference" noises reflects learning of their acoustic details.

RESULTS: Listeners with dyslexia did not differ from controls in any aspect of the task, qualitatively or quantitatively. They required the same amount of training to achieve discrimination of repeated from nonrepeated noises, and they learned the reference noises as often and as rapidly as the control group. However, they did show all the hallmarks of dyslexia, including a well-characterized phonological deficit.

CONCLUSION: The data did not support the hypothesis that deficits in basic auditory processing or nonverbal learning and memory are the cause of the phonological deficit in dyslexia.