LANGUAGE LEARNING: NONHUMAN PRIMATES

Guided by modern evolutionary theory, scientists have been able to explicate the origin of the morphology of the human body. However, the evolution of the human mind has yet to be so satisfactorily accounted for. Comparative psychology has already succeeded in providing evidence to help clarify the biobehavioral origins of human language and symbolic competence through studies of our nearest living relatives—the Pongidae (chimpanzee, Pan ; orangutan, Pongo ; and gorilla, Gorilla). These great apes are substantially more like humans than are the lesser apes, monkeys, or any other mammals. The similarities between human and chimpanzee DNA exceed 98 percent. Genetic relatedness enhances the probability that life forms will have similar psychology as well as appearance. Consequently, we might reasonably expect to find linguistic and cognitive competencies in the ape that are similar to those observed in humans.

Early Studies

Speculation that apes might be capable of language began in the nineteenth century. Early in the twentieth century, occasional studies were undertaken to determine whether or not this might be true, but none succeeded. Efforts were renewed in the mid-1960s, with studies by the Gardners (Gardner and Gardner, 1969; Gardner, Gardner, and van Cantfort, 1989) and by Premack (1971, 1976). The Gardners used American Sign Language, and Premack used plastic tokens of different shapes and colors to function as words, with the aim of establishing two-way communication and an experimental analysis of language functions, respectively. Their chimpanzees, Washoe and Sarah, learned relatively large numbers of signs and tokens and, seemingly, their appropriate use.

Project LANA

In 1971, the LANA Project was initiated by Rumbaugh and his colleagues. A computer-based research system provided Lana, a chimpanzee, with a keyboard that held 125 keys, each embossed with a distinctive geometric symbol called a lexigram (see Figure 1). Lexigrams functioned as words, and their concatenation was computer-monitored for correctness. The computer could activate a bank of devices, some of which delivered various foods and drinks, movies, slides, and music. Lana readily learned her lexigrams in order to request things and to give the names and colors of objects. Tests revealed that she saw Munsel color chips in a manner that resembles the way humans see them, an observation reaffirmed by Matsuzawa (1985) in Japan with the chimpanzee Ai.

Within limits, Lana demonstrated her ability to modify her sentences so as to achieve ends other than the specific ones for which they were designated, such as using them to attract attention to malfunctioning food vendors and to the devices that produced slides and music. A cucumber was innovatively called "banana which-is green," an overly ripe banana was called "banana which-is black," and an orange was called "apple which-is orange (colored)." Comprehensive analyses clearly indicated that Lana's productions could not be satisfactorily attributed either to rotely learned sequences or to imitation. Project LANA contributed what was perhaps the first successful application of a computer to a system for communicative research. Romski, Sevcik, and Pate (1988) have demonstrated that keyboards similar to the one developed for LANA augment the communicative effectiveness of children with language deficits. Project LANA also affirmed the ability of the chimpanzee to learn large numbers of symbols, to use them in prescribed sequences, to alter use of those sequences creatively, and to use symbols so as to facilitate perceptions of sameness and difference between items when one was presented visually and the other by touch.

Other Language-Learning Projects with Chimpanzees

Terrace (1979) began Project Nim in the early 1970s. The chimpanzee Nim learned signs, but Terrace concluded that Nim's signs—and also those of the Gardners' Washoe—were predominantly partial or complete imitations of the human researchers working with these apeshad recently signed. (As noted, imitation was not an issue in the LANA Project because the project was carried out using a computer to monitor and record Lana's lexigram utterances.)

Also in the 1970s, Miles (1990) began Project Chantek. Chantek, an orangutan, was taught manual signs; Miles concluded that Chantek's signing was not confounded by or due to his imitation of human signers, as Terrace had claimed to be the case with Nim and Washoe.

Research of the mid-and late 1970s by Savage-Rumbaugh and Rumbaugh with two chimpanzees named Sherman and Austin used a variation of Lana's keyboard. These chimpanzees demonstrated their abilities to classify lexigrams, each of which represented a specific food or tool, through the use of two other lexigrams, glossed as food and tool, embedded among more than one hundred other keys on their keyboard. This ability to categorize lexigrams was strong evidence that each symbol did, in fact, represent an item to the apes and that they could use these representations, on trial-1 tests in controlled conditions, to classify almost without error the symbols of their working vocabulary.

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Studies with Bonobos

Research by Savage-Rumbaugh with the bonobo (Pan paniscus), a species apart from the common chimpanzee (P. troglodytes), was the first to demonstrate the chimpanzee's ability to learn the meanings of symbols spontaneously. The bonobo came to comprehend the meanings of lexigrams, and even human speech, prior to developing competence in use of the keyboard. All previous apes had been able to "talk" (e.g., produce signs, use tokens, use lexigrams) as a result of specific training programs, but their comprehension skills were either deferred or never assessed. For the first time, a model of language learning in the ape tracked or paralleled the course of language acquisition in the normal child. Early experience from birth has been critical for such observational learning of language to occur in the bonobo. The common chimpanzee also benefits similarly from such rearing, though possibly to a lesser degree than does the bonobo (Brakke and Savage-Rumbaugh, 1995a; Brakke and Savage-Rumbaugh, 1995b).

One bonobo, Kanzi, responded appropriately to about three-fourths of more than seven hundred novel requests presented to him verbally under controlled test conditions to preclude cuing. His performance was generally comparable with that of a two-year-old girl whose mental age was two and a half years. Neither Kanzi nor the girl had the benefit of people modeling the requests, nor had they been trained to do what was requested of them. The conclusion is, then, that they comprehended the syntax of the novel requests conveyed by normal human speech.

Kanzi not only comprehends single spoken utterances, he also participates in linguistically mediated communicative interactions with humans in which both Kanzi and his human counterparts employ a variety of communicative modalities concomitantly (e.g., lexigram use, gesture, vocalization, speech). These exchanges share characteristics with human conversations, as Kanzi participates in turn taking, responds to commands, and makes requests of his own. Taglialatela and Savage-Rumbaugh (2001) have reported that during these conversations, Kanzi produces acoustically distinct vocal utterances that vary with the semantic context in which they are produced.

Conclusion

Language competence rests fundamentally in an individual's ability to comprehend, process, and produce meaningful utterances. Chimpanzees can come to acquire and use human language if raised in an environment that permits the emergence of these abilities. It is no longer reasonable to insist that the potential for language is unique to the human species—and reason, according to Descartes, should be humans' strongest suit.

See also:COMPARATIVE COGNITION; LANGUAGE LEARNING: HUMANS

Bibliography

Brakke, K. E., and Savage-Rumbaugh, E. S. (1995a). The development of language skills in bonobo and chimpanzee, Part 1: Comprehension. Language and Communication 15, 121-148.

—— (1995b). The development of language skills in bonobo and chimpanzee, Part 2: Production. Language and Communication 16, 361-380.

Gardner, B. T., and Gardner, R. A. (1969). Teaching sign language to a chimpanzee. Science 162, 664-672.

Gardner, R. A., Gardner, B. T., and van Cantfort, T. E. (1989). Teaching sign language to chimpanzees. Albany: State University of New York Press.

Greenfield, P. M., and Savage-Rumbaugh, E. S. (1990). Grammatical combination in Pan paniscus : Processes of learning and invention in the evolution and development of language. In S. T. Parker and K. R. Gibson, eds., "Language" and intelligence in monkeys and apes: Comparative developmental perspectives, pp. 540-578. New York: Cambridge University Press.

Matsuzawa, T. (1985). Color naming and classification in a chimpanzee (Pan troglodytes). Journal of Human Evolution 14, 283-291.

Miles, H. L. W. (1990). The cognitive foundations for reference in a signing orangutan. In S. T. Parker and K. R. Gibson, eds., "Language" and intelligence in monkeys and apes: Comparative developmental perspectives, pp. 511-539. New York: Cambridge University Press.

Premack, D. (1971). On the assessment of language competence in the chimpanzee. In A. M. Schrier and F. Stollnitz, eds., Behavior of nonhuman primates, Vol. 4, 186-228. New York: Academic Press.

—— (1976). Language and intelligence in ape and man. Hillsdale, NJ: Erlbaum.

Romski, M. A., Sevcik, R. A., and Pate, J. L. (1988). The establishment of symbolic communication in persons with mental retardation. Journal of Speech and Hearing Disorders 53, 94-107.

Rumbaugh, D. M. (1977). Language learning by a chimpanzee: The Lana Project. New York: Academic Press.

Savage-Rumbaugh, E. S. (1986). Ape language: From conditioned response to symbol. New York: Columbia University Press.

Taglialatela, J. P., and Savage-Rumbaugh, S. (2001). Bonobo cognition: Expectations, explications, and conversations. Paper presented at the 109th convention of the American Psychological Association. San Francisco, CA.

Terrace, H. S. (1979). Nim. New York: Knopf.

Duane M.Rumbaugh

E. SueSavage-Rumbaugh

Revised byDuane M.Rumbaugh,

E. SueSavage-Rumbaugh,

andJared P.Taglialatela