Self-recognition in chimpanzees and orangutans, but not gorillas
Recognition of one's own reflection in a mirror qualifies as an objective test of self-awareness. Although most primates appear incapable of learning that their behavior is the source of the behavior depicted in a mirror, the present study replicates previous reports showing that both chimpanzees and orangutans are capable of self-recognition. As the only remaining species of great ape, gorillas were also systematically tested with mirrors. Using a specially designed control procedure which provides independent evidence of interest in and motivation to touch unobtrusively applied marks used to assess self-recognition, gorillas appeared unable to correctly decipher mirrored information about themselves.