The title The mentalities of gorillas and orangutans: Comparative perspectives was inspired by Köhler's famous book The mentality of apes (1927), in which apes were implicitly equated with chimpanzees. This book focuses on two other great apes that were less known in Köhler's day. It is the fourth in a related series of edited volumes on cognition of great apes. The first volume, “Language” and intelligence in monkeys and apes (Parker & Gibson, 1990), emphasized the importance of using models from developmental psychology to compare the cognitive and symbolic abilities of monkeys, apes, and humans. The second volume, Self-awareness in animals and humans (Parker, Mitchell, & Boccia, 1994), used developmental frameworks to compare manifestations of self-awareness in monkeys, apes, and humans. It was aimed at broadening the scope of research in this subject to extend beyond the classical mark test for mirror self-recognition. The third volume, Reaching into thought (Russon, Bard, and Parker, 1996), focused on cognitive abilities of great apes using models from developmental psychology, but extended the scope to include studies in wild populations. This most recent volume continues the tradition of using models from developmental psychology to compare the cognitive abilities of great apes, and that of including studies from both captive and wild populations. It also expands the preview to include studies of taxonomy and phylogeny (Begun, this volume) and the brain (Semendeferi, this volume). It differs from the other volumes in focusing primarily on gorillas and orangutans. The aim of this volume is to redress the chimpocentric imbalance in attention to chimpanzees and bonobos at the expense of the other great apes.

CAN AN APE LEARN LANGUAGE?

In 1887, Müller challenged Darwin to demonstrate the truth of human evolution by teaching language to an ape. More than 100 years later, scientists are no longer worried about supporting claims of human evolution, but they are still teaching apes aspects of human language and discerning what apes understand. With more than 30 great apes from all four species exposed to some level of language learning and human culture, it is possible to make preliminary comparisons among the great apes. The abilities of chimpanzees and bonobos have been extensively reviewed (Desmond, 1979; Gardner, Gardner, & Van Cantfort, 1989; Savage-Rumbaugh, 1991; Wallman, 1992), but less is known about gorillas and orangutans (Ristau, 1996). In this chapter, I summarize the ape language studies, compare the language abilities of all great ape species, and discuss specific issues such as methodology, vocabulary, symbolic capacity, communicative competence, reference, and grammar. To begin, I describe briefly three types of language-learning studies: those based on speech, those based on gesture, and those based on arbitrary visual symbols.

SPEECH STUDIES

Perhaps the first study to teach an ape some aspect of human language was Garner's (1900, p. 138) attempt to teach the chimpanzee Moses four words with “a bribe of corned beef”: the English “mamma,” the French “feu,” the German “wie,” and the Nkami “nkgwe”. Moses learned to say “feu,” and imitated the mouth movements of “mamma,” but was less successful with the other two sounds.

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).

Introduction

Beginning in the 1960s, Gardner and Gardner (1969), Premack (1972), and Rumbaugh, Gill, and von Glasersfeld (1973) first demonstrated that chimpanzees could represent words or ideas using a set of gestural signs, computer lexigrams, or plastic tokens. In subsequent research, Fouts (1973), Miles (1976, 1983), Patterson (1978), and Terrace, Petitto, Sanders, and Bever (1979) extended these language studies of the gorilla and orangutan and expanded the focus to such issues as ape-to-ape communication, discourse ability, and the relationship between language and other cognitive processes. Controversy arose over the degree to which an ape's use of these systems could be called “language,” the extent of animal linguistic abilities, and whether or not other species, such as aquatic mammals and birds, could exhibit similar skills (Brown, 1973; Epstein, Lanza, & Skinner, 1980; Le May & Geschwind, 1975; Limber, 1977; Mounin, 1976; Pepperberg, P&G18); Sebeok & Umiker-Sebeok, 1980; Terrace et al., 1979).

Project Chantek is an attempt to advance our knowledge of animal intelligence and “language” ability through a developmental perspective. It consists of a longitudinal sign language study with an orangutan named Chantek. The orangutan is the only great ape from Asia (the chimpanzee and gorilla are found in Africa). The orangutan was thought by many to be less likely to develop language skills than chimpanzees, primarily because of beliefs that chimpanzees are more intelligent and evidence that the African apes had a more recent evolutionary separation from humans than did the orangutan.