Infant viewing of social scenes is under genetic control and atypical in autism

Long before infants reach, crawl, or walk, they explore the world by looking: they look to learn and to engage(1), giving preferential attention to social stimuli including faces(2), face-like stimuli(3), and biological motion(4). This capacity—social visual engagement—shapes typical infant development from birth(5) and is pathognomonically impaired in children affected by autism(6). Here we show that variation in viewing of social scenes—including levels of preferential attention and the timing, direction, and targeting of individual eye movements—is strongly influenced by genetic factors, with effects directly traceable to the active seeking of social information(7). In a series of eye-tracking experiments conducted with 338 toddlers—including 166 epidemiologically-ascertained twins, 88 non-twins with autism, and 84 singleton controls—we find high monozygotic twin-twin concordance (0.91) and relatively low dizygotic concordance (0.35). Moreover, the measures that are most highly heritable, preferential attention to eye and mouth regions of the face, are also those that are differentially diminished in children with autism (Χ(2)=64.03, P<0.0001). These results—which implicate social visual engagement as a neurodevelopmental endophenotype—not only for autism, but for population-wide variation in social-information-seeking(8)—reveal a means of human biological niche construction, with phenotypic differences emerging from the interaction of individual genotypes with early life experience(7).