Primate Language

Curiosity regarding apes' capacity for language has a long history. From DARWIN's nineteenth century postulations of both biological and psychological continuities between animals and humans, to the more recent discovery (Sibley and Ahlquist 1987) that chimpanzee (Pan) DNA is more similar to human than to gorilla (Gorilla) DNA, scientific findings have encouraged research into the language potential of apes. A recent report (Gannon et al. 1998) that the chimpanzee planum temporale is enlarged in the left hemisphere, with a humanlike pattern of Wernicke's brain language-area homolog, will provide additional impetus. That area is held basic to human language. Does, in fact, elaboration in the chimpanzee's planum temporale provide for language-relevant processes or potential? Is its elaboration an instance of homoplasy (convergent evolution)? Or is its function not necessarily related to language?

Language research with apes was revitalized in the 1960s as Beatrix and Allen Gardner (Gardner, Gardner, and Cantfort 1989) used a variation of American Sign Language to establish two-way communication with their chimpanzee, Washoe, and as David Premack (Premack and Premack 1983) used an artificial language system of plastic tokens with his chimpanzee, Sarah. In the 1970s, Sue Savage- Rumbaugh's group (1977) developed a computer-monitored keyboard of distinctive geometric patterns, called lexigrams, to foster studies of language capacity with Lana, a chimpanzee. Herbert Terrace's (1979) chimpanzee Project Nim, Lynn Miles's (1990) orangutan Project Chantek, and Roger and Deborah Fouts's (1989) project with Washoe and other chimpanzees obtained from the Gardners also started during the '70s.

These projects initially emphasized language production. It was assumed that if an ape appropriately produced a sign then it must also understand its meaning. That assumption proved unwarranted. Apes were proved capable of selecting seemingly appropriate symbols without understanding their meanings, even at a level grasped by 2- and 3-year-old children as they use words. Studies of comprehension ensued.

But how can one assess whether symbol meaningfulness and comprehension are present, given that apes can't speak? There are several ways. First, the meaningfulness of symbols with Sherman and Austin chimpanzees (Savage- Rumbaugh 1986) was documented by their symbol-based, cross-modal matching. Without specific training, they could look at a lexigram and select the appropriate object, by touch, from others in a box into which they could not see. They also could label, by use of word-lexigrams, single objects that they could feel but not see. Second, and more importantly, they learned word-lexigrams for the categories of "food" and "tool" to which they appropriately sorted 17 individual lexigrams, each representing a specific food and implement. (Each lexigram represented either a food or a tool, such as a banana, magnet, cheese, lever, etc.) Thus, their lexigrams represented things not necessarily present -- the essence of SEMANTICS or word meaning.

Comprehension became of special interest with the discovery that Kanzi, a bonobo (a rare species of chimpanzee, Pan paniscus), spontaneously learned the meanings of word-lexigrams and later came to understand human speech -- both single words and novel sentences of request (Savage-Rumbaugh et al. 1993). The discovery was made in the course of research with Matata, his adoptive mother. Matata's essential failure in learning lexigrams was likely a reflection of her feral birth and development.

Though always present during Matata's language training, Kanzi was not taught; but later, when separated from her, it became clear that he had learned a great deal! Spontaneously, he began to request and go get specific foods and drinks, to label objects, and to announce what he was about to do with the appropriate lexigrams.

From that time forward, Kanzi was reared in an even richer language-structured milieu. Caregivers commented on events (present, future, and past) and particularly on things of special interest to him. Where possible, caregivers used word-lexigrams as they spoke specific words. Kanzi was not required to use a keyboard to receive objects or to participate in activities and was given no formal lessons.

Kanzi quickly learned by observation how to ask to travel to specific sites in the forest, to play a number of games, to visit other chimps, to get and even cook specific foods, and to watch television. He also commented on things and events and continued to announce eminent actions. In sharp contrast with our other apes, Kanzi also began to comprehend human speech -- not just single words but also sentences.

Consequently, Kanzi's (8 yrs.) speech comprehension was compared with that of a human child, Alia (2 yrs.). In controlled tests, they were given 415 novel requests -- to take a specific object to a stated location or person ("Take the gorilla (doll) to the bedroom"), to do something to an object ("Hammer the snake!"), to do something with a specific object relative to another object ("Put a rubber band on your ball"), to go somewhere and retrieve a specific object ("Get the telephone that's outdoors"), and so on. An ever-changing variety of objects was present on each trial, and the ape and child were asked to fulfil various requests with them. Each request was novel and had not been modeled by others.

Both Kanzi and Alia were about 70 percent correct in carrying out the requests on their first presentation. As with the human child, Kanzi's comprehension skills outpaced those of production. Kanzi understood much more than he "could say." Though his comprehension skills compared favorably with those of a 2½-year-old child, his productive skills were more limited and approximate those of the average 1 to 1½-year-old child (Greenfield and Savage- Rumbaugh 1993). These major findings were replicated in subsequent research with two other apes (Savage- Rumbaugh and Lewin 1994).

Thus, speech comprehension can be acquired spontaneously (e.g., without formal training) by apes if from birth they are reared much as one would rear human children -- with language used by caregivers throughout the day to describe, to announce, and to coordinate social activities (i.e., feeding, traveling, and playing).

These findings indicate that language acquisition (1) is based in the social-communicative experiences of early infancy; (2) is based, first, in comprehension, not production or speech; and (3) is based in the evolutionary processes that have selected for primate taxa that have large and complex brains (Rumbaugh, Savage-Rumbaugh, and Washburn 1996).

Thus, the question should not be, "Do apes have language?" Given a brain only about one third the size of ours, it would be unreasonable to expect the ape to have full competence for language and its several dimensions. Rather, the question should be, "Which aspects of language can they acquire, and under what conditions do they do so?"

Just as the discovery of even elementary forms of life on another planet will not be trivialized, the documentation of elementary language competence in species other than humans has significant implications for the understanding of evolution and brain. Although the capacity for acquiring even elementary language skills is surely limited among animal species, at least some ape, marine mammal, and avian species have capacities that include the abilities to name, to request, to comprehend, and both to use and to comprehend symbols as representations of things and events not necessarily present in space and time. These capacities are inherently in the domain of language.

Additional links

-- Duane Rumbaugh and Sue Savage-Rumbaugh

References

Fouts, R. S., and D. H. Fouts. (1989). Loulis in conversation with cross-fostered chimpanzees. In R. A. Gardner, B. T. Gardner, and T. E. Van Cantfort, Eds., Teaching Sign Language in Chimpanzees. Albany: SUNY Press.

Gannon, P. J., R. L. Holloway, D. C. Broadfield, and A. R. Braun. (1998). Asymmetry of chimpanzee planum temporale: Humanlike pattern of Wernicke's brain language area homolog. Science 279:220-222.

Gardner, R. A., B. T. Gardner, and T. E. Van Cantfort. (1989). Teaching Sign Language to Chimpanzee. New York: SUNY Press.

Greenfield, P. M., and E. S. Savage-Rumbaugh. (1993). Comparing communicative competence in child and chimp: The pragmatics. Journal of Child Language 20:1-26.

Miles, L. (1990). The cognitive foundations for reference in a signing orangutan. In "Language" and Intelligence in Monkeys and Apes: Comparative Developmental Perspectives. Cambridge: Cambridge University Press, pp. 511-539.

Premack, D., and A. J. Premack. (1983). The Mind of an Ape. New York: Norton Company.

Rumbaugh, D. M. (1977). Language Learning by a Chimpanzee: The LANA Project. New York: Academic Press.

Rumbaugh, D. M., E. S. Savage-Rumbaugh, and D. A. Washburn. (1996). Toward a new outlook on primate learning and behavior: Complex learning and emergent processes in comparative psychology. Japanese Psychological Research 38:113-125.

Savage-Rumbaugh, E. S. (1986). Ape Language: From Conditioned Response to Symbol. New York: Columbia University Press.

Savage-Rumbaugh, E. S., and R. Lewin. (1994). Kanzi: The Ape at the Brink of the Human Mind. New York: Wiley.

Savage-Rumbaugh, E. S., J. Murphy, R. A. Sevcik, K. E. Brakke, S. Williams, and D. M. Rumbaugh. (1993). Language comprehension in ape and child. Monographs of the Society for Research in Child Development no. 233, 58:3-4.

Sibley, C. C., and J. E. Ahlquist. (1987). DNA hybridization evidence of hominoid phylogeny: Results from an expanded data set. Journal of Molecular Evolution 26:99-121.

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

Primate Language

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References

Further Readings