Atypical development of the neural networks associated with infants' predisposition to attend to faces may disrupt experience-dependent specialization within the social brain, and it may give rise to atypical patterns of specialization. Not surprisingly, these propositions are being tested in infants at elevated risk for autism spectrum disorder (ASD). Lacking the normative bias toward faces is expected to limit social experience and opportunities for social learning and thereby to exacerbate atypical brain development. According to this social motivation theory of autism (1), interest in faces should be diminished early in life among infants later diagnosed with ASD. The theory is supported by evidence that atypical social attention is one of the earliest behavioral markers of ASD, often apparent by 12 months of age (see [2] for a review). Given that bias toward faces is typically evident from birth (3) and that there is neural-level evidence of ASD as early as 6 months (4), the social motivation theory justifies exploration of the effects of ASD on social attention during the first year of life. Retrospective studies of ASD during infancy using home videos report attenuated social attention by 6 months of age, but prospective studies of infants at risk for ASD have provided scant evidence of atypical social attention before the first birthday (2).
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