Comparison of auditory stimulus processing in normal and autistic adolescents.

This experiment investigated the possibility that autistic adolescents may avoid speech communication with the world around them by "tuning out" or perceptually suppressing auditory speech stimuli. The tune-out auditory suppression hypothesis was investigated using the subject's own speech as the stimulus under three perceptual-motor conditions: with speech in a delayed auditory feedback (DAF) mode, with a white noise masking speech mode, and with speech in a normal, quiet listening mode. Five autistic adolescents were compared with six normal controls on speech time duration and sound level. DAF increased the speech sound pressure level (SPL) and increased speech time duration for both groups.