Autism and the Brain by Tatyana B Glezerman

Author:Tatyana B Glezerman
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

7.7.3 Laughter in Autistic Children

Hudenko, Stone, and Bachrowski (2009) conducted an acoustic analysis of laughter as part of emotional expression in normal and autistic children. First they described the acoustic structure of laughter that includes two qualitatively different components: voiced and unvoiced. Voiced laughter is periodic and contains a fundamental frequency; perceptually, it has a tonal, song-like quality. In contrast, unvoiced laughter is aperiodic, it is largely atonal and noisier, produced with turbulence arising in the supralaryngeal cavities. Only voiced laughter is strongly associated with the experience of positive affect. Unvoiced laughter is used to negotiate the subtleties of social interaction, for example, “grunt-like” unvoiced laughs affirming others during conversation. These laughs are only loosely coupled with an individual’s internal affective state.

This experimental study revealed a qualitative difference in the expression of laughter between children with and without autism. Children with autism did not produce unvoiced laughter, in striking contrast to nonautistic children whose laughs were 37–48 % unvoiced. The authors concluded that laughter in children with autism reflects their internal state. They indicated that children with autism do experience positive affect, and this state is signaled with voiced laughter. They also found individually specific rhythmical characteristics of voiced laughter in children with autism.

The acoustic properties of voiced laughter described in this study suggest its relation to the thalamic level’s inner rhythm. Also note that voiced laughter is similar to the RH-associated affective prosody (emotion in voice).

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