Pitch and Volume Stability in the Communicative Response of Adults with Autism

In this study, we investigate the characteristics of prosody in a newly developed speech experiment to objectively and quantitatively characterize prosodic features of autism spectral disorder (ASD). In the experiment, male adults with high-functioning ASD and age-, intelligence-level-matched males with typical development (TD) read aloud 29 brief scripts as if they were responding to the preceding auditory stimuli. On the basis of the hypothesis that autistic speakers tend to react in a stereotypical manner regardless of the situation, we quantitively evaluated the difference between their responses to stimuli of the same script by different speakers in terms of the prosodic features, such as fundamental frequency, intensity, and mora duration. The results showed that the individuals with ASD had similar pitch registers or volume levels, whereas those with TD reacted in higher maximum pitches or intensities to the male voice in some tasks. This result may be related to the recently reported stability of pitch control in autistic speakers. In contrast, regarding the ‘disgust’ emotion, the mean absolute error of intensity between the reactions to two actors was higher in the ASD group than in the TD group.