Instrumental learning of traits versus rewards: dissociable neural correlates and effects on choice :: Leor M Hackel, Bradley B Doll, David M Amodio, New York University, Columbia University :: www.nature.com/neuro
Summary and review of the above article
Humans can look beyond immediate positive and negative experiences, and can additionally encode behavioural traits. Both learning from reward and learning from traits involve processing in the ventral striatum. Learning about traits allows another person to be valued in contexts other than the immediate one, and this can be important in social decision-taking.
Rewards and generosity
In a study that allowed participants to assess both the reward-value of interactions and the relative generosity of such interactions, it was shown that participants relied more on the relative generosity than the absolute reward obtained from interactions. This happened although the optimal strategy was indicated as being to ignore the degree of generosity shown.
Prediction errors between expected and received reward and expected and actual generosity were both processed in the right ventral striatum. Feed- back for the trait of generosity was seen to be independent of the level of reward. However, predictions for generosity are also encoded in brain regions that are not involved with reward, such as the left ventrolateral prefrontal, precuneus, posterior cingulate and temporoparietal junction.
In making choices, the influence of generosity was shown to be greater than the influence of absolute rewards. After tasks had been completed, generosity was more important than reward-value for subsequent behavioural choices. The ventromedial prefrontal is a brain region associated with value signals, and this area is also responsive to differences in generosity. Generosity and value signals are thought to be combined.