Acoustic analysis of oral productions of infants later diagnosed with autism and their mother.

Research on early signs of autism in social interactions often focuses on infants' motor behaviors; few studies have focused on speech characteristics. This study examines infant-directed speech of mothers of infants later diagnosed with autism (LDA; n = 12) or of typically developing infants (TD; n = 11) as well as infants' productions (13 LDA, 13 TD). Since LDA infants appear to behave differently in the first months of life, it can affect the functioning of dyadic interactions, especially the first vocal productions, sensitive to expressiveness and emotions sharing. We assumed that in the first 6 months of life, prosodic characteristics (mean duration, mean pitch, and intonative contour types) will be different in dyads with autism. We extracted infants' and mothers' vocal productions from family home movies and analyzed the mean duration and pitch as well as the pitch contours in interactive episodes. Results show that mothers of LDA infants use relatively shorter productions as compared to mothers talking to TD infants. LDA infants' productions are not different in duration or pitch, but they use less complex modulated productions (i.e., those with more than two melodic modulations) than do TD. Further studies should focus on developmental profiles in the first year, analyzing prosody monthly.