Failure to find self-recognition in mother-infant and infant-infant rhesus monkey pairs.

To date, chimpanzees, orangutans, and humans are the only species which have been shown capable of recognizing themselves in mirrors. In an attempt to make the identity of the reflection more explicit we report two experiments in which rhesus monkeys were given paired access to a common mirror over an extended period. While developmental differences in mirror behavior were obtained, signs of self-recognition failed to emerge. The results were discussed in terms of the absence in monkeys of an essential cognitive category for processing mirrored information about the self.