Structure and acoustics of the speech of verbal autistic preschoolers

In this study, we report an extensive investigation of the structural language and acoustical specificities of the spontaneous speech of ten three- to five-year-old verbal autistic children. The autistic children were compared to a group of ten typically developing children matched pairwise on chronological age, nonverbal IQ and socioeconomic status, and groupwise on verbal IQ and gender on various measures of structural language (phonetic inventory, lexical diversity and morpho-syntactic complexity) and a series of acoustical measures of speech (mean and range fundamental frequency, a formant dispersion index, syllable duration, jitter and shimmer). Results showed that, overall, the structure and acoustics of the verbal autistic children's speech were highly similar to those of the TD children. Few remaining atypicalities in the speech of autistic children lay in a restricted use of different vocabulary items, a somewhat diminished morpho-syntactic complexity, and a slightly exaggerated syllable duration.