Strategic incentives undermine gaze as a signal of prosocial motives

People often have to judge the social motives of others, for example, to distinguish truly prosocial people from those merely trying to appear prosocial. Gaze can reveal the motives underlying social decisions, as decision-makers dedicate more attention to motive-relevant information. We extend the use of eye-tracking and apply it as a communication device by providing (real-time) eye-tracking information of one participant to another. We find that untrained observers can judge the prosociality of decision-makers from their eye-tracked gaze alone, but only if there are no strategic incentives to be chosen for a future interaction. When there are such strategic incentives, the cues of prosociality are invalidated, as both individualistic and prosocial decision-makers put effort into appearing more prosocial. Overall, we find that gaze carries information about a person's prosociality, but also that gaze is malleable and affected by strategic considerations.