Communicative dysfunction is a characteristic feature of Autism Spectrum Disorder (ASD). Despite the universal nature of the impairment, studies have failed to characterise vocalisations from ASD populations due to inconsistent discriminative patterns in speech and the heterogeneity of the disorder. Recent advances have established that there is an early brain dysfunction in autism which intensive intervention can alter. Given this scenario, it is possible that children with ASD have a delayed developmental trajectory and milestones followed by typical children might manifest at later time points.
The objective of this study was to find a consistent pattern in vocalisations of children with Autism Spectrum Disorders. Based on literature, which demonstrates the manifestation of ‘atypical’ prosody or pitch patterns in ASD speech, our hypothesis places a delayed developmental trajectory as cause for deviant pitch patterns in ASD speech.
Spontaneous speech recordings of 15 high-functioning, verbal children with ASD (AUT) and 10 age-matched typical controls (TD) in the age group 4-10 years was obtained. Similar spontaneous recordings, of 8 mothers interacting with their 6-18 month-old neurotypical infants, were made. Following this, intonation patterns of children with ASD were compared with age-matched controls to determine differences in mean pitch, pitch range, pitch excursion and the nature of intonation contours, and compared with simliar patterns obtained from child-directed interactions
Our findings show that pitch patterns of children with ASD with verbal ability are different from age-matched typically developing children. Pitch patterns of the AUT group are characterized by exaggerated intonation contours, elevated pitch, higher pitch range and pitch excursion as compared to TD. It has also been shown that such exaggerated pitch patterns are also distinguishing features of motherese as demonstrated by analysis of child-directed vocalizations of mothers in the MOT group.
Typically developing children respond to the prominent intonation contours of motherese prior to adult-like speech development and grow out of it by 2-3 years. These pitch patterns characterized by exaggerated contours are exhibited by AUT group at a later age of 4-10 years, suggesting that these features might follow a delayed developmental trajectory. Our preliminary findings suggest a basis for continued use of motherese-like speech in enhancing verbal communication in subpopulations of ASD individuals. Future research will aim at exploring these possibilities in greater detail.