INDIVIDUALLY DISTINCTIVE ODORS REPRESENT INDIVIDUAL CONSPECIFICS IN RATS

Individual recognition implies that a subject has the ability to discr iminate between familiar conspecifics on the basis of their idiosyncra tic characteristics. In this sense it is likely to be a more complex p rocess than other forms of social recognition which involve classifica tion of conspecifics into broad categories such as group, sex, age, ki nship and familiarity. Using a go/no-go discrimination procedure, this study showed that rats, Rattus norvegicus, are indeed able to recogni ze conspecifics as individuals. Once rats had learned to discriminate a pair of conspecifics, they showed positive transfer on a series of d iscrimination problems involving novel conspecifics as stimuli. Furthe rmore, on a reversal test, rats were able to retain the memory of the individual identity of conspecifics to which they were exposed for the first time for at least 24 h. Finally, using the individually distinc tive odours of previously discriminated conspecifics in tests clearly demonstrated that rats perceive olfactory signatures as representation s of known individuals. Taken together, these results provide evidence for true individual recognition in rats and invite further investigat ions to gain deeper insight into the cognitive processes used by rats to build up a representation of individual conspecifics. (C) 1997 The Association for the Study of Animal Behaviour.