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.