Infant-Directed Speech and Infants Who Are at-Risk or Later Diagnosed with Autism Spectrum Disorder: A Scoping Review

Background: In infants later diagnosed with autism (LDA), differences in language and social-communication development may be apparent in the first year of life and well before diagnosis, which usually only occurs after two years of age. Infant-directed speech (IDS) used by primary caregivers is a crucial component in an infant’s early life, contributing to language and social-communication development. IDS is the universal speech register used when interacting with an infant. It involves the use of specific prosodic, lexical, and syntactic characteristics which aid in infant language and socio-communicative development. Parents use IDS that is matched to their infant’s developmental status, and they react and adjust their IDS based on infant cues. As such, knowledge about the characteristics of IDS use with infants at-risk for Autism Spectrum Disorder (ASD) may inform our understanding of the early emergence of ASD.

Objectives: The aim of this study was to conduct a scoping review of the literature examining IDS use with infants who are either high-risk (HR) for ASD or LDA.

Methods: Six databases were searched, and articles were screened against inclusion and exclusion criteria. Studies were selected that examined IDS with an infant aged 4 years or younger and who was at HR (familial, genetic, screened as HR) for ASD or LDA. Articles that were focussed on parent intervention involving a change in interaction quality, or examined infant preference for IDS without reporting on the IDS characteristics of the speaker, were excluded. Grey literature was included.

Results: 30 articles met the final inclusion criteria and were included in the scoping review. Most of the articles (N=26) focussed on maternal IDS, although four studies also analysed paternal IDS. Four studies reported that the amount of follow-in comments (utterances synchronous with the infant’s focus of attention) spoken by parents predicted infant language outcomes in LDA infants. Parents were reported to respond less contingently to HR or LDA infants (N=4). Parents of HR or LDA infants were also reported to speak more directive and intense IDS (N=4), used less melodic prosody (N=2) and used more non-verbal behaviours alongside IDS when compared to parents of typically developing or low-risk (LR) infants (N=2). Parents were also often reported to elicit less name calling but more attention bids during interactions with their HR or LDA infant (N=5). Articles reported mixed results in terms of the amount of IDS spoken by parents, some studies found parents spoke less or used less IDS overall to their HR or LDA infant (N=5), however some studies did not report any differences (N=4).

Conclusions: The findings from this review indicate that parents of HR or LDA infants use IDS differently to parents of a LR or typically developing infant. These studies strongly support the idea that even before infants are diagnosed with autism, parents can pick up on differences displayed by their infant. The findings of these studies provide evidence that they are related to infant language and social-communication outcomes and should therefore be considered as an important factor when considering interventional strategies.