Summary
Here we demonstrate that during strategic gameplay monkeys behave as if they reason recursively about other individuals’ beliefs and desires in order to predict their choices and to guide their own actions, especially the decision to cooperate. Neurons in mid superior temporal sulcus (mSTS), the putative homolog of the human temporo-parietal junction (TPJ), signal abstract non-perceptual social information, including payoffs, intentions, and outcomes, and further distinguish between social and nonsocial agents while monkeys play the game. We demonstrate for the first time that a subpopulation of these neurons selectively signals cooperatively obtained rewards. Neurons in the anterior cingulate gyrus (ACCg), an area implicated in vicarious reinforcement and empathy, do not distinguish agency and as a population carry less information about strategic variables. These findings suggest the capacity to mentalize has deep roots in the strategic social behavior of primates, and endorse mSTS as the evolutionary wellspring of these functions.
