Gaze crossing: a new paradigm to assess social contingency and word learning during real-time infant–adult interactions

Children's social interactions with caregivers play a crucial role in their development. One strong cue to an ongoing social interaction is the mutual dependency of interaction partners' behaviours, a feature we refer to as social contingency. Socially contingent interactions have been shown to support learning, but it remains underexplored whether social contingency alone, even in the absence of other social cues, can drive developmental advantages. Addressing this question requires faithfully representing bi-directional contingency in infant-adult interactions while isolating it from other social cues. Building on the perceptual crossing paradigm, we designed an innovative setup where infants and adults interact in real time using eye gaze, with all interactions mediated through a non-social, screen-based display. Extending beyond the one-way responsiveness in previous studies, this setup captures bi-directional contingency through dependencies in gaze movement upon mutual detection. Our findings demonstrate that social contingency modifies infant behaviour even in such a streamlined context. To extend the paradigm's applicability, we integrated it with word learning, a task sensitive to the concurrent effect of social interaction. Preliminary evidence suggests that contingency facilitates word learning, underscoring the potential of the gaze-crossing paradigm to further elucidate the role of contingency in child development. This article is part of the theme issue 'Mechanisms of learning from social interaction'.