Introduction

Several studies of how chimpanzees (Pan troglodytes) and orangutans (Pongo pygmaeus) respond to their reflections in a mirror have established that these primates share with humans the capacity for self-recognition (Gallup, 1970; Lethmate & Dücker, 1973; Miles, SAAH16; Suarez & Gallup, 1981). Recent data on gorillas (Gorilla gorilla) (Patterson & Cohn, SAAH17; Swartz & Evans, SAAH11) strongly suggest that these great apes also are capable of self-recognition. Although the relationship between mirror self-recognition (MSR) and self-awareness in the sense used by social psychologists remains to be clarified (see Mitchell, SAAH6), there is general agreement that selfrecognition implies the existence of some kind of cognitive (as opposed to a merely kinesthetic) self-awareness. This may in turn allow for the expression of a range of behaviors reflecting a “theory of mind” (Crook, 1988; Gallup, 1982; Humphrey, 1984; Whiten, 1991), although the relationship between self-recognition and theory of mind (ToM) remains to be clarified, as certain subjects (e.g., autistic children, Baron-Cohen, 1992) may show the former but not the latter (Gergely, SAAH5; Mitchell, 1993).

In contrast to the numerous demonstrations of self-recognition in great apes, studies of reactions to mirror-image stimulation (MIS) in monkeys have consistently failed to find evidence of self-recognition (reviews: Anderson, 1984a; Gallup, 1987). It has been suggested that the contrasting performances between great apes and monkeys on tests of self-recognition reflect the existence of a fundamental difference in cognition – concerning self-awareness – between the self-recognizing Pongidae and other nonhuman primates (Gallup, 1982, 1987).