An approach to emotion is described in which emotions are defined as states elicited by instrumental reinforcers, that is, by stimuli that are the goals for action. This leads to a theory of the evolutionary adaptive value of emotions, which is that different genes specify different goals in their own self-interest, and any actions can then be learned and performed by instrumental learning to obtain the goals. The brain mechanisms for emotion in brain regions such as the orbitofrontal and anterior (...) cingulate cortex provide a foundation for understanding the neural basis of emotion. Classically conditioned effects may modulate the actions initiated by this system. In addition to this instrumental learning system, some stimuli may elicit responses, for example approach, withdrawal, or fixed action patterns, but intervening states are not required for this type of adaptive response. In addition, a rational thought system involved in multistep planning can allow gene-specified goals to be deferred or avoided in order to achieve longer-term types of goals that may be more advantageous to the individual than to the genes. (shrink)