Eyes on social development : Aetiology of infant gaze patterns and links to later socio-communicative abilities and autism

Sammanfattning: Already at a very early age, infants preferentially attend to social stimuli. Although this is believed to be important for later social cognition and learning, little is known about the aetiology of infant social attention and associations to later abilities.In this thesis, I used eye tracking to study the influence of genes and environment on individual differences in different aspects of social attention, and developmental outcomes across different domains in toddlerhood in relation to both typical and atypical development. In Study I, the influence of genes and environment on the preference for looking at eyes versus mouth (eye-mouth-index) was assessed in 5-month-old twins. The eye-mouth-index was highly heritable, and a stronger tendency to look at the eyes was associated with later language comprehension. In Study II, sustained attention to faces was assessed in the same sample of infants, and found to be moderately heritable. Longer sustained attention was associated with more socio-communicative behaviours in toddlerhood. In Study III, videos of children interacting were shown to 18-month-olds with and without an elevated likelihood of autism. At specific time intervals in the videos, there was a significant difference in gaze allocation between the toddlers who did and did not receive an autism diagnosis later in childhood.The findings of this thesis suggest that both sustained attention to faces and eye versus mouth preference are heritable, meaning that young infants may select their environment based on their genotype, by looking at different aspects of a scene or a face. Being exposed to different types of input might influence later development, and these results indicate that social attention is associated with later social and communicative abilities, as well as later autism. In summary, this thesis contributes to the understanding of early social attention and how different aspects of this phenomenon are related to later development.