Language development and its relationship to theory of mind in children with high-functioning autism
Impairments in language, prosodic and theory of mind (ToM) ability in individuals with high-functioning autism (HFA) have been widely reported. However, this PhD study is the first to investigate changes in receptive and expressive prosody skills over time. This is also the first study to report on the relationship between prosody and ToM, independent of language ability. Additionally, this study presents a new adaptation of a ToM assessment, on which prosodic and verbal input are carefully controlled. Language, prosody and ToM skills in 24 children aged 9 to 16 years with HFA were assessed approximately 2 1/2 years after participation in a study of language and prosody conducted at Queen Margaret University College (McCann, Peppe, Gibbon, O'Hare and Rutherford, 2006). The current study reports the skills and abilities of the children with HFA in the follow-up, using a battery of speech and language assessments, as well as assessments of expressive and receptive prosody and ToM abilities. The majority of the children with HFA continue to show expressive and receptive language impairments, with expressive language ability continuing to be the most impaired language skill, mirroring results at Time point 1. Children with HFA are developing language along the same, but delayed, developmental trajectory as children with typical development. Strong growth was noted on prosodic ability within structured tasks, as measured by the total score on the prosody assessment, as compared to verbal-age matched typically developing children. The statistical gap that was present between groups in the earlier study no longer remains. However, children with HFA continue to perform worse on the understanding and use of contrastive stress. Children who showed atypical sounding expressive prosody in conversational speech in the earlier study continue to do so in the follow-up. Children with HFA are developing early ToM abilities with the same developmental progress as typically developing children, but at a chronological age approximately seven years behind. However, children with HFA struggle with second-order ToM tasks. Results show that language, prosody and ToM abilities are highly correlated. Prosody and ToM show a relationship independent of language ability. Implications of these findings to theoretical understanding, future research, as well as to speech and language assessment and intervention are presented.