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Abstract
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Objectives
It is known that persons afflicted with autism often have deviant prosodic features in their speech. For example, they may have a limited range of intonation, their speech can be overly fast, jerky or loud, or it can be characterized by large pitch excursions, quiet voice, inconsistent pause structure, deviant word stress and/or by creaky or nasal voice. These features can constitute a significant obstacle to the social acceptance of the individual. Indeed, deviant prosodic features may create an immediate impression of “oddness”, and they affect autistic speakers’ ratings of social and communicative competence.
The aim of this study is to provide a phonetic description of prosodic features occurring in slightly autistic preadolescents’ speech as well as to find out which prosodic features of their speech neurotypical persons find salient. The following parameters have been taken into account: loudness, pitch, speech rate, rhythm, pauses, stressing, and quality of voice.
Methods
The study has been carried out by methods of instrumental and experimental phonetics. The data come from naturally occurring interaction. The data include two therapy sessions with two different groups, where altogether seven (n=7) 11–13-year-old Finnish-speaking boys talk with their therapists. The acoustic features of the boys’ speech were then analyzed by methods of instrumental phonetics.
In addition, 40 neurotypical Finnish-speaking subjects performed a perception test where they assessed their impressions concerning the salience of different prosodic features of the autistic boys’ speech on the basis of 14 sound samples.
Results
All seven informants have salient prosodic features in their speech, but individual differences concerning the number of these features are very big: where one of the participants has deviant features in all fields, another one only has a ‘creaky voice’.
Conclusion
According to this study, speech rhythm is the prosodic parameter that includes most deviant features in autistic preadolescents’ speech. Pauses, which naturally constitute an important rhythmic factor, also appear to be a highly salient characteristic. Pitch and the level of loudness are often considered to be deviant, too. Concerning the pitch, it is noteworthy that pitch excursions – that is, melodic rises and falls – are assessed to be salient much more frequently than flat pitch, which is “traditionally” considered to be typical of people afflicted with autism.
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