Social stimuli and social rewards in primate learning and cognition.

Many studies have suggested that non-human primates have good individual recognition abilities, that social stimuli can serve as discriminative stimuli in learning tests and that visual access to social objects or events can be a reinforcer for operant behaviour. Intensified research efforts comparing the effectiveness of social and non-social stimuli and rewards across a range of learning and other cognitive tasks would help clarify the extent to which monkeys and apes might be specially predisposed to process information in the social domain. In addition to identity, social interactions and relationships constitute raw material to be mentally represented and processed. Some studies have addressed the individual and evolutionary origins of mechanisms underlying the ability to attribute mental states and intentions to others, for example by looking at the understanding of another's gaze, imitation and the development of tactical deception. The results of some of this research suggest that only some species might be capable of higher-order attribution. Further progress in the study of primate social cognition will require continuing refinement of methods and the development of new techniques to compare primates as behaviourists and mentalists.