Change in selectivity of infant social behavior between 15 and 30 weeks

Six infants were filmed at 15 and 30 weeks of age while alone as well as in the presence of an adult (mother or stranger) who interacted with the infant or remained passive. Judges viewing samples of infant behavior tried to identify the social context in which episodes of behavior had occurred. Signal detection analysis of ratings made by the judges showed that infant behavior at both ages varied in accord with whether or not an adult was present. The identity and interactional style of the adult had only limited influence on infant behavior at 15 weeks, but judges could readily establish from the behavior of 30-week infants whether the adult was interactive or passive. Mothers were no more accurate in their ratings of social context than other judges were, even when they were observing the behavior of their own infant. Measurement of specific infant behaviors showed that the presence of the adult at both ages and the interactional style of the adult at 30 weeks exerted selective influence over rates of looking and smiling by infants. Signal detection classification was more sensitive to social context variables than microanalysis, possibly because observers had access to complex behavioral configurations.