The Role of Social Communication in Later Language: an Exploratory Study of Infants Later Diagnosed With Autism and Typically Developing Infants




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Social communication refers to the use of verbal and non-verbal skills in social interactions and encompasses social attention, communication, and symbolic skills. These skills are thought to play an important role in the development of receptive and expressive language. The overarching goal of this dissertation is to evaluate associations between early social communication skills and later language abilities using longitudinal data. The first study in this dissertation explored early social communication skills across three groups: infants with a high probability for autism, who are later diagnosed with autism (HP-ASD), infants with a high probability for autism, who are not later diagnosed with autism (HP-Neg), and infants with a low probability for autism, who are not later diagnosed with autism (LP-Neg). Early social communication skills are a harbinger for later cognitive and language development in infants who develop autism. Hence, investigating these skills in infancy may help shed light on early risk markers and treatment targets. The objective of this study was to examine group differences in social communication skills and explore associations between social communication skills measured at 12-months and language abilities measured at 24-months. HP-ASD infants demonstrated social communication deficits as early as 12-months-of-age, well before autism diagnoses are considered stable. Overall, social communication scores were associated with later receptive and expressive language; however, this association was not significant in the HP-ASD infants. Although previous research has reported associations between social communication and later language in autistic toddlers, the current study explored this association in the youngest sample to date. From a developmental perspective, it is likely that HP-ASD infants had not acquired social communication skills at 12- months that are associated to later language. The second study explored longitudinal trajectories of visual social attention to talking faces in typically developing infants, and the third study explored associations between visual social attention and later language. Previous studies that have used eye tracking to explore developmental changes in visual social attention to the eyes and mouth of talking faces have reported a pattern of increasing attention to the mouth starting at about 8 months of age and peaking at 2 years. This increase in attention to the mouth has been found to be associated with later expressive language abilities. However, longitudinal eye tracking data with frequent sampling across development enabled us to capture drastic shifts in attention between the eyes and mouth of talking faces and enhance our understanding of the putative relationship between visual social attention and later language abilities. The second and third studies of this dissertation focused on expanding on existing research by examining visual social attention in a longitudinal data set and implementing stringent eye tracking quality controls. Typically developing infants did not demonstrate significant changes in visual social attention to the eyes and mouth across development, and gaze patterns were not significantly associated with later language skills. It is likely that a single developmental pattern of visual social attention did not emerge because of high individual variability and small sample sizes. In summary, visual social attention measured using eye tracking was not found to support language development in typically developing infants. However, social communication skills extracted from an observational standardized assessment were associated with later receptive and expressive language. Results also presented compelling evidence for early social communication deficits in HP-ASD infants. The results of this study will inform treatment targets for presymptomatic autism interventions.



Health Sciences, Speech Pathology, Psychology, Developmental