Human social interactions are regulated by moral norms that define individual obligations and rights. These norms are enforced by punishment of transgressors and reward of followers. Yet, the generality and strength of this drive to punish or reward is unclear, especially when people are not personally involved in the situation and when the actual impact of their sanction is only indirect, i.e....

Because humans and animals encounter various situations, the ability to adaptively decide upon responses to any situation is essential. To date, however, decision processes and the underlying neural substrates have been investigated under specific conditions; thus, little is known about how various conditions influence one another in these processes. In this study, we designed a binary choice t...

The dorsomedial striatum (DMS) has been implicated in the acquisition of reward representations, a proposal leading to the hypothesis that it should play a role in situations involving reward loss. We report the results of an experiment in which the effects of DMS excitotoxic lesions were tested in consummatory successive negative contrast (reward devaluation), autoshaping training with partial...

The detection of differences between predictions and actual outcomes is important for associative learning and for selecting actions according to their potential future reward. There are reports that tonically active neurons (TANs) in the primate striatum may carry information about errors in the prediction of rewards. However, this property seems to be expressed in classical conditioning tasks...

Experimental work in animals has identified numerous neural structures involved in reward processing and reward-dependent learning. Until recently, this work provided the primary basis for speculations about the neural substrates of human reward processing. The widespread use of neuroimaging technology has changed this situation dramatically over the past decade through the use of PET and fMRI....

Gharib, Derby, and Roberts (2001) proposed that reducing reward expectation increases variation of response form. We tested this rule in a new situation and asked if it also applied to variation of response location and timing. In 2 discrete-trial experiments, pigeons pecked colored circles for food. The circles were of 6 possible colors, each associated with a different probability of reward. ...

A decrease in sensitivity to pleasurable stimuli, anhedonia, is a major symptom of depression in humans. Several animal models have been developed to simulate this symptom (e.g. drug withdrawal, learned helplessness) using reward-sensitive procedures such as intracranial self-stimulation and progressive ratio responding as a measure of reward function. Recently, we introduced the use of another...