Economic theory and practice has long been dominated by the view that people are driven by self-interest. Research in psychology and in the emerging field of behavioral economics has shown that this model of human motivation is wrong. This research showed that people are not only driven by self-interest. They also have strong tendencies to cooperate. It seems we view others' interests as an end in itself, too. This not only applies to relatives and friends but also to strangers. However, what we are taught about human nature affects what we belief and how we behave. For example, research by Robert H. Frank and his colleagues (1993) has shown that students of economics, as they were more and more exposed to this axiom of self-interest which formed the basis of dominant theories of economics, they became less and less social and cooperative.
Social: why our brains are wired to connect, Matt Lieberman writes about the work of neuroscientist James Rilling who has conducted fMRI studies of subjects playing prisoner's dilemma games.
Previous research has shown that the brain looks differently when we are complying with the social norm than when we are choosing on the basis of our own preferences. When we comply with the social norm lateral parts of the prefrontal cortex which, among other things, inhibit our desires, are active. When we follow our own preferences, the reward system in brain regions such as the ventral striatum are active.
In a prisoner's dilemma when both players do not cooperate (defect), they both get nothing. When one player defects and the other cooperates, the defector gets the maximum and the cooperator gets nothing. When both cooperate they both get a medium reward. Rilling observed more ventral striatum activity when players chose to cooperate then when they chose to defect. In other words, they felt more reward about the total outcome for both players than for their personal outcome. The lateral prefrontal regions were not involved when cooperation was chosen. This suggests that for people cooperation is an end it itself, not self-interest in disguise. These results were not only found in studies in which players had to play the prisoners's dilemma games multiple times against each other but also when they had to play only one time. However, when the subjects played the game against a computer instead of against a real person, mutual cooperation did not activate the reward system.