Comparing the neural basis of decision making in social dilemmas of people with different social value orientations, a fMRI study.

Using functional MRI, we investigate the neural correlates of intrinsic versus extrinsic motivation to cooperate by comparing people who differ in the personality trait Social Value Orientation. Participants (n 28) played several one-shot prisoner’s dilemma games (offering weak cooperative incentives) and coordination games (offering strong cooperative incentives) with anonymous partners while they were under the scanner. Behavioral results indicate that proself individuals adjust their behavior toward more cooperation when extrinsic incentives were present, while prosocials’ decisions are not affected by game context. The neurological data is consistent with a priori developed hypotheses regarding different behavioral strategies, and suggest that extrinsically motivated proself strategies are driven by calculation and a situation-by-situation approach. Increased activation was found in dorsolateral prefrontal cortex, posterior superior temporal sulcus (STS), and precuneus. Intrinsically motivated prosocials’ strategies reflect norm compliance, routine moral judgment, and social awareness. Increased activation was found in lateral orbitofrontal cortex, anterior STS, and inferior parietal lobule.