Measuring beliefs and rewards: A neuroeconomic approach

The neurotransmitter dopamine is central to the emerging discipline of neuroeconomics; it is hypothesized to encode the difference between expected and realized rewards and thereby to mediate belief formation and choice. We develop the first formal tests of this theory of dopaminergic function, based on a recent axiomatization by Caplin and Dean (Quarterly Journal of Economics, 123 (2008), 663-702). These tests are satisfied by neural activity in the nucleus accumbens, an area rich in dopamine receptors. We find evidence for separate positive and negative reward prediction error signals, suggesting that behavioral asymmetries in responses to losses and gains may parallel asymmetries in nucleus accumbens activity.