The investigation of animal cognition is currently an active area of research in comparative psychology. Such cognitive processes as representation of lists (Swartz, Chen, & Terrace, 1991), complex strategies of spatial memory (Cook, Brown, & Riley, 1985), use of numbers (Boysen & Berntson 1989), and acquisition of concepts (D'Amato & Van Sant, 1988; Herrnstein & Loveland, 1964; Oden, Thompson, & Premack, 1990) have been addressed in primate and nonprimate species. One of the most exciting topics relevant to both comparative and developmental psychology has been that of mirror selfrecognition (MSR), with its implications for comparative cognition (see Gallup, 1982, 1991; Gallup & Suarez, 1986; Mitchell, 1993; Parker, 1991; Swartz, 1990).

This phenomenon, first demonstrated in chimpanzees by Gallup (1970), involves two empirical observations that have been interpreted as evidence of self-recognition. When first exposed to a mirror, chimpanzees showed socially appropriate behaviors directed toward the mirror, as though the reflection were another conspecific. As mirror exposure continued, the chimpanzees' behavior changed. Social behaviors waned and self-directed or selfreferred behaviors appeared. Self-directed behaviors involve using the mirror to guide movements to areas of the body not visible without the aid of the mirror; self-referred behaviors involve manipulation of the environment while watching the action in the mirror. The appearance of self-directed behaviors was interpreted as indicative of self-recognition on the part of the chimpanzee (Gallup, 1970).