Michael L. Platt
Duke Institute for Brain Sciences, Center for Cognitive Neuroscience, Duke University

We are the most charitable species on the planet—often giving to others we don’t even know. We are also among the most competitive—misleading, lying, and cheating to further our own ends. How the brain shapes these choices remains poorly understood. I will describe recent work using a new model of social decision making in which pairs of monkeys interact through a computer device while we either monitor or manipulate their brains. We found that monkeys favor choices that reward another monkey, particularly if he is more familiar or subordinate, rather than choosing to reward no one. Oxytocin—a hormone implicated in social bonding—increases both prosocial choices and attention to the other monkey. We also found that prosocial choices selectively activated neurons in the medial frontal cortex, an area implicated in empathy in humans. By contrast, when monkeys played a competitive game against each other, they rapidly developed unpredictable behaviors that served to mislead the other monkey. We found that deceptive tactics selectively activated a specific population of cells in the lateral frontal cortex. Inactivating these neurons impaired deceptive planning. Together, these discoveries define part of a network of brain areas specialized for complex social behavior and cognition.