Introduction

The investigation of the linguistic and cognitive abilities of great apes offers insights into self-awareness by providing the additional modality of language with which self-awareness can be investigated in animals (see Patterson & Cohn, SAAH17). In ape language experiments, chimpanzees, gorillas, and an orangutan have been enculturated in human settings and have learned to communicate according to human linguistic and cultural conventions using a set of gestural signs, computer lexigrams, or plastic tokens (Fouts, 1973; Gardner & Gardner, 1969; Miles, 1980,1986; Patterson, 1978; Premack, 1972; Rumbaugh, Gill, & von Glaserfeld, 1973; Savage-Rumbaugh, 1986; Terrace, Petitto, Sanders, & Bever, 1979).

These studies provide several major advantages for investigating selfawareness in animals. First, they permit us to study self-awareness in our closest biological relatives, the great apes, with whom we share a large number of biological and behavioral similarities. A relatively small number of genetic alterations are required to extrapolate humans and all of the great apes from a theoretical common ancestor most like the orangutan (Yunis & Prakash, 1982). The orangutan karyotype is the most conservative (primitive), with humans and the African apes displaying more derived features (Mai, 1983; Schwartz, 1987; Stanyon & Chiarelli, 1982; Weiss, 1987). This interpretation is also supported by fossil data (Pilbeam, 1982). Thus, the orangutan, having the most pleisiomorphic traits of the great apes, is the most primitive and has been termed “a living fossil” (Lewin, 1983).