A meta-analysis of prosody in autism, Williams syndrome, and Down syndrome

Prosody, the rhythm and melody of speech, is an important component of effective communication, and it is an area of difficulty for many populations who struggle with communication. This paper is a meta-analysis of nine studies (and two sets of unpublished data) that assessed prosody using the Profiling Elements of Prosody in Speech-Communication (PEPS-C; Peppé & McCann, 2003) in autism spectrum disorder, Williams syndrome, and Down syndrome. Our original goal was to include studies involving any neurodevelopmental disorder that is commonly associated with intellectual disability, yet our systematic search, which included three databases (i.e., PsychInfo, ERIC, and PubMed), only identified studies involving these three groups. To be included in the meta-analysis, studies had to include a group (n ≥ 3 participants) with a neurodevelopmental disorder commonly associated with intellectual disability and a typically developing comparison group matched on chronological age, nonverbal abilities, or verbal abilities. Studies also needed to report original data using the PEPS-C and be available in English. Study quality was assessed using a checklist adapted from Downes et al. (2016). Results revealed that prosodic form was a weakness for each etiology, while unique patterns of strengths and weaknesses were evident for prosodic functions. Groups with autism (n = 5), all classified as high-functioning or with Asperger's syndrome, exhibited weakness in emotional affect but some relative strengths with turn-end and focus tasks. Groups with Williams syndrome (n = 4) demonstrated weaknesses on phrase/sentence-level tasks and relative strengths on word-level tasks. Groups with Down syndrome (n = 2) had the greatest difficulty overall, though performance was better on receptive (vs. expressive) function tasks. By combining studies and related subtasks of the PEPS-C, we are able to more confidently generalize findings for each population and identify targets for intervention. However, given the limited number of studies identified, this paper also highlights the need for more research on prosody in intellectual disability.