From faces to hands: Changing visual input in the first two years.

Human development takes place in a social context. Two pervasive sources of social information are faces and hands. Here, we provide the first report of the visual frequency of faces and hands in the everyday scenes available to infants. These scenes were collected by having infants wear head cameras during unconstrained everyday activities. Our corpus of 143hours of infant-perspective scenes, collected from 34 infants aged 1month to 2years, was sampled for analysis at 1/5Hz. The major finding from this corpus is that the faces and hands of social partners are not equally available throughout the first two years of life. Instead, there is an earlier period of dense face input and a later period of dense hand input. At all ages, hands in these scenes were primarily in contact with objects and the spatio-temporal co-occurrence of hands and faces was greater than expected by chance. The orderliness of the shift from faces to hands suggests a principled transition in the contents of visual experiences and is discussed in terms of the role of developmental gates on the timing and statistics of visual experiences.