Human infants detect other people's interactions based on complex patterns of kinematic information.

Do infants perceive other people's interactions by means of a mechanism that integrates biological motion information across the observed individuals? In support of this view, the present study demonstrates that infants (N = 28, Age  = 14 months) discriminate between point light displays representing disrupted and non-disrupted interactions between people, even though the two interaction types are identical at the level of individual point light agents. Moreover, a second experiment (sample 2: N = 28, Age  = 14 months) indicated that visual preference in this context is influenced by an audiovisual integration processes that takes into account the presence of an interaction between people. All these results were found exclusively for upright displays--when stimuli were shown upside-down (disrupting biological motion processing), performance was random. Collectively, these findings point to an important role for biological motion in social perception in human infants.