Novel Research Paradigms to Investigate Social Development in Typically Developing Infants and Infants at Elevated Risk for Autism Spectrum Disorder

A large body of research has examined social developmental processes in typically developing infants in the first year of life, and more recently in infants at higher familial risk for autism spectrum disorder (infant siblings) in order to uncover early behavioural markers for the disorder, essential for early diagnosis. The social stimuli presented in earlier research were often not representative of social experiences in the real world. For studies focussing exclusively on typical development, the use of inadequate stimuli means that the extent to which they produce findings that generalize to 'real world' social interactions is unclear. For the line of research involving infant siblings, these methodological issues have resulted in an ambiguous pattern of results. To address these issues, this thesis presents novel research methods that more closely approximate the interactive context in which social interaction typically occurs. This was achieved by developing a novel face scanning method - the gaze-contingency eye-tracking paradigm - in which infants could 'interact' with on-screen faces by fixating certain pre-specified regions of the face, providing a more realistic and socially demanding experience. Norms for typical behaviour within this paradigm were established (Chapter 3) and contrasted with behaviour from a sample of infant siblings (Chapter 3 & 4). The findings indicate that infant siblings show reduced social responsiveness relative to typically developing infants in this paradigm. These results were corroborated in an infant-parent free play task (Chapter 5), validating the efficacy of the gaze-contingency paradigm. Finally, infants' ability to follow human conversations as an observer was tested with novel cartoon stimuli providing evidence of early social understanding in typical development (Chapter 6). The novel methods are reviewed in terms of their added value to the field and findings are discussed in relation to their implications for typical and atypical development.