Are you human? The engagement in real-time social interactions recruits the reward system


An intrinsic motivation for social interaction has often been proposed and is thought to be unique to the human species. However, little is known about underlying neural mechanisms. Here, we investigated whether experiencing engagement in social interaction recruits the reward system of the brain. A combined eye-tracking and fMRI paradigm was used in which participants interacted with a virtual agent in a series of gaze-based interactions in real-time. To create situations in which they experience the interaction as social or as non-social, they were made believe that during each block the agent’s gaze behavior could either be controlled by another human participant or a computer algorithm. The other participant was a confederate of the experimenter, which enabled experimental control of the agent's gaze reactions. After each block participants had to indicate whether they experienced the interaction as social or not. Results demonstrated that gaze-based interactions with a perceived human partner is associated with activity in the ventral striatum, a core component of reward-related neurocircuitry, while interactions with a computer-driven agent activate attention networks. In addition, the nature of the interaction with a human partner (naive vs. cooperative) differentially modulates striatal activity.

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