Data for: Efficiency as a principle for social preferences in infancy

Two separate research lines have shown first that infants expect agents to move efficiently toward goal-states and second that they navigate the social world selectively, preferring some individuals to others, and attributing social preferences to others’ agents. Here, we studied the relationship between infants’ expectations of efficient actions and their capacities to identify appropriate social partners. We presented 15-month-old infants with a set of videos containing three geometric figures depicting social agents. One of them (observer) watched how the other two agents acted to obtain a reward. Critically, the efficiency of their actions was manipulated. One agent reached the reward taking a direct efficient path (efficient agent), while the other took a curvilinear inefficient path (inefficient agent). At test, the observer approached each of them in two separate trials. Infants looked longer at the screen when the observer approached the inefficient rather than the efficient agent. In addition, they showed a bias to track the actions of the efficient agent when efficient and inefficient agents acted simultaneously. In a second experiment, we rejected the possibility that infants’ expectations in experiment 1 resulted from differences in the movement repertoire of the agents. The two studies suggest that infants use action efficiency as a cue to identify appropriate partners. They exploit this information to tune their attention and to predict others’ social interactions.