Speaker
Description
Cooperation in primate species relies on advanced social cognition, but the behavioral and neural mechanisms supporting cooperative behaviors remain unclear. To investigate this, we examined freely moving marmoset dyads in a cooperative lever-pulling task. Marmosets successfully coordinated their actions, relying on social vision rather than environmental cues. Causal dependencies between social gaze and pull actions revealed both gaze-dependent and gaze-independent strategies. Cooperation depended on social relationships, including dominance, kinship, and sex. Remarkably, marmosets adapted their strategies based on partner identity, indicating rapid social learning and memory. Building on decision neuroscience frameworks, we hypothesized that social gaze functions as a mechanism for accumulating social evidence prior to cooperative actions, supported by the dorsomedial prefrontal cortex (dmPFC). Using a wireless neural recording system in a naturalistic setting, we found enhanced social gaze before successful pull actions. Single-neuron analyses revealed that dmPFC firing rate slopes were modulated by gaze accumulation—shallower slopes occurred with more gaze accumulation, mirroring ramping patterns observed in decision-making studies. At the population level, dmPFC principal component trajectories were longer when more gaze accumulation was required, especially during mutual cooperation. These findings show that the dmPFC encodes accumulated social evidence through both neural and population dynamics, supporting a distributed mechanism for naturalistic social decision-making. Taken together, they provide new insights into the behavioral and neural mechanisms underlying cooperative interactions and underscore the importance of social gaze in coordinating real-world cooperation.
