Contingency enables the formation of social expectations about an artificial agent.

What environmental regularities support infant communicative learning from social interactions? We propose that infants allocate their attention toward and learn from external events that are contingent on their own behaviors. We tested the robustness of the influence of contingency on communicative learning by using a non-biological stimulus, a remote-controlled car, as the social partner. The car approached infants and produced a speech sound either contingently to infants' vocalizations or on a yoked schedule. Two additional groups had an unfamiliar human experimenter as their social partner in contingent and yoked control conditions. We assessed whether infants formed expectations about their partner's responsiveness to their vocalizations. Expectations made based on contingent responsiveness would support the role of contingency in promoting plasticity in early communicative learning. Infants across all conditions increased their vocalization rates when their partner paused in responding, suggesting that they expected their vocalizations to influence their partners' behavior. Infants vocalized significantly more to the social partner than their caregiver if they received contingent rather than yoked responses from the social partner, regardless of if the partner was a human or non-biological agent. Contingent responses to prelinguistic vocalizations facilitated the formation of expectations for interactivity of social partners.