Actions are often learnt incidentally by observing other individuals. How aspects inherent to the social context in which an action is seen affect action learning remains poorly understood. Here we study the effect of a special social signal, the eye gaze of the demonstrator, on the immediate and delayed memory and execution of observed actions. In Experiment 1, healthy young adult volunteers (N = 37) watched short videos of a demonstrator performing novel actions with novel objects only once, and were tested for immediate and delayed recall of those actions through action execution. Overall, novel actions on novel objects were recalled more accurately if, during demonstration, the demonstrator had repeatedly gazed towards the participant (direct gaze) versus towards an object (control condition). Experiment 2 (N = 41) investigated the immediate and delayed recall of novel and familiar object-use actions performed on familiar objects. In this condition, which involved familiar information, direct gaze had no effect or was even detrimental for recall. These findings show that direct gaze benefits incidental learning and retention of novel information only (novel actions paired with novel objects in Experiment 1), and interferes with the retention of familiar information (familiar objects paired with familiar actions in Experiment 2). This study suggests a role of ostensive eye contact in incidentally learning new actions. At the same time, it limits its beneficial role to a specific type of learning scenario, one involving only novel (as opposed to familiar) information, unveiling the selective function of ostensive eye contact in the transmission of novel cultural behaviors.
