Intonation and emotion in autistic spectrum disorders

The classic picture of an autistic individual includes an impoverished ability to interpret or express emotion. The prosody of spoken language in autistic children is thought to lack emotional content. In this study, the verbal intonation of children with autism was examined and compared to that of children with Asperger Syndrome (AS) and normal controls (ctrl). Utterances elicited by repetition and by spontaneous story completion were analyzed by quantifying phonetic features (pitch, amplitude, and length) and comparing them to subjective ratings of produced emotion (happy, sad or angry). Since the most consistent phonetic correlate of these emotional targets has been demonstrated to be pitch range, speakers with autistic spectrum disorders were expected to have decreased pitch range; however in the repetition task, autistic subjects actually had a larger pitch range than the other groups. Other measures of intonation including amplitude, duration, and location of pitch peak revealed defects that are more complex than predicted. In spontaneous speech, autistic subjects performed more poorly on both phonetic targets and subjective ratings than ctrls, and AS subjects fell between autistics and normals.