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Primate Use of Language
Created by Lauren Kosseff

Research concerning the ability of primates to acquire language has profound implications for the understanding of the evolution of the human species.  The acquisition of language in primates may shed light on the  development of language in early humans.  In this sense, research of primate language and primate tool use offer similar insight into our early ancestors. 

Many people believe that language is a unique capacity of humans.  Doubters of the ability of primates to use language include renowned M.I.T. linguist Noam Chomsky and cognitive scientist Steven Pinker.  Chomsky's Universal Grammar theory clearly defines language as a skill limited to humans, the sole possessors of the cognitive hardware which makes language possible.   Chomsky makes an analogy to flying in order to illustrate his position on primate language: "Humans can fly about 30 feet-that's what they do in the Olympics.  Is that flying?  The question is totally meaningless."  Chomsky and his followers theorize that the neural requirements for language developed in humans after the evolutionary split between humans and primates.   They base their argument on the ease with which children acquire language in comparison to the difficulty exhibited by primates.  To Chomsky and his followers, this disparity demonstrates the presence of an innate propensity for language in children which is not present in primates.  Pinker posits the argument that primates can be trained to do incredible things, however, these trained behaviors do not signify language ability. He believes that the primates simply learn to press certain buttons in order to receive rewards. 

Dr. Sue Savage-Rumbaugh is a researcher who strongly believes in the ability of primates to use language.  One of her most impressive observations involved a bonobo chimpanzee named Kanzi.  Savage-Rumbaugh tried to no avail to train Kanzi's adoptive mother to use a keyboard of symbols.  The researchers were surprised to find that Kanzi had been eavesdropping on his mother's lessons and had acquired a substantial vocabulary.  From then on, Kanzi was not given structured training like his mother, but was taught while walking through the forest with his trainers.  By the age of 6, Kanzi had acquired a vocabulary of 200 words and was able to construct sentences by combining words with gestures or with other words.   Kanzi's most notable accomplishment was captured on videotape: he was told, "Give the dog a shot," and he proceeded to inject his stuffed dog with a syringe.  Savage-Rumbaugh argues that Kanzi's language was initially dependent upon contextual cues, but that once he mastered a substantial vocabulary, he could respond accurately to 70% of novel commands from a concealed speaker.   Critics say that Kanzi's accomplishments are not proof of language ability in primates because the crucial element in language ability is production, not comprehension.  

Observation of the vervet species of monkeys in the wild offers support for the ability of primates to use language.  The vervet monkeys have demonstrated the most advanced primate system of communication in their natural environment.  The sounds which the vervets produce as a means of communication are instinctive and not learned.

Sign Language

Sign language has been chosen as the superior medium in which to conduct language instruction for primates because they are unable to vocalize language.   Some researchers hold the belief that primates are simply not intelligent enough to speak.  This theory has lost credence as further research with apes has demonstrated their tremendous intellectual capacities in other arenas.  Another possible explanation of the inability of primates to acquire verbal language, posited by Robert Yerkes, is that Primates are not inclined towards imitation of sounds and therefore cannot learn verbal language.  A final theory suggests that the vocal cords of primates are not capable of supporting the production of language.


Washoe is a chimpanzee who was taught to sign by her caretakers, Allen and Beatrice Gardner.  She was raised in a friendly environment in which she learned sign language both through imitation and instrumental learning.  Her language acquisition was notable in several respects.  Washoe was able to transfer signs to a new referent without specific instruction.  For example, she learned the word "more" in relation to tickling but was spontaneously able to apply the term to another referent.   Additionally significant was Washoe's use of signs in combinations after learning only about 8 or 10 signs.  This spontaneous combination of signs seems similar to the ability of human children to connect words in sentences to which they have never specifically been exposed.  Washoe has demonstrated reliable use of 240 signs.   A sign is deemed reliable when its use has been recorded by three separate observers on 15 consecutive days.  Her trainers have observed that Washoe mostly uses her signs to discipline her children and explain her concern about them. 

...and Loulis

Washoe adopted an infant chimp named Loulis.  No human sign language was used in Loulis' presence during the first 5 years of her life.  Remarkably, Loulis nonetheless acquired more than 50 signs by watching the other chimps.  Bob Ingersoll, who studied Washoe and Loulis, observed that there was little active teaching on the part of the adult chimps.  Loulis' language acquisition thus reflects the manner in which human children acquire language.  The Gardners concluded from Loulis' acquisition of language through observation of the other chimps that: "once introduced, sign language is robust and self-reporting, unlike the systems that depend on special apparatuses such as the Rumbaugh keyboards or the Premack plastic tokens."


Herb Terrace doubted that primate language is any sort of equivalent of human language.  He did not believe that the findings of language acquisition and use in Washoe, Loulis, and other primates were truly symbolic of language acquisition.   Instead, he theorized that there were simpler explanations for the behaviors which had been interpreted as language use by primates (Morgan's Canon!).  Terrace posited that the primates were performing rote memorization tasks similar to pigeons who are taught to peck at colors in specific orders.  Terrace also thought that primates only signed in order to please their trainers, not for the personal gratification of using the signs.  Terrace also says that a primate might learn to connect a sign with food and reproduce the sign through simple conditioning, just as Pavlov's dogs were conditioned to salivate at the sound of a bell.

Therefore, Terrace decided to conduct his own study of primate language use.  He raised a chimpanzee, Nim, as a human child and taught him sign language in the manner in which Washoe had been taught.  Nim did in fact demonstrate some important aspects of language use.  He was observed using the signs for "angry" and "bite" to express his displeasure, an important observation in that it demonstrates the use of arbitrary symbols to represent physical actions.  Despite his acquisition and use of numerous signs, Terrace decided that Nim was incapable of combining words to create novel ideas.  The only occasions in which Nim produced combinations of signs were imitations of signs previously produced by his trainers.

Central Washington University's Chimpanzee
and Human Communication Institute

The CHCI at Central Washington University is home to a family of 5 chimps who, according to their trainers, have mastered the use of sign language and implement it in conversations with each other and their trainers.  The chimps at CHCI use the signs alone and in combination with other signs.  One of the longest recorded sentences produced by a chimp contained 7 signs!  Chimps generally utilize their signs in discussing aspects of family life.  The trainers have observed that young males frequently sign to talk about games, such as tickle and chase. 

An important finding about primate language use at the CHCI is that the chimps use signs to refer to natural language categories.  For example, the chimps use one sign signifying "dog" to refer to all dogs.  This category generalization is similar to that of children as they first begin learning to speak.  Chimpanzees have also shown that they are able to create novel signs by combining signs to convey a metaphorically different concept.  For example, one chimp at the CHCI was recorded describing a watermelon as "drink fruit."  Seems like a pretty accurate description! 

The CHCI is considering a couple of possible continuations of their research, provided that funding is available.  One possible area of exploration is the ability of chimps to use signs to represent spatial relationships and their capacity for taking on the position of another person (or chimp).  Additionally, the CHCI is considering studying the ability of chimps to recognize break-downs in conversations and to repair them, their use grammatical markers, and their ability to understand and use temporal signs.

The CHCI also hopes to expand their research to include the study of how to apply the teaching of language to chimps to assisting autistic children, who have difficulty learning language.  They also hope that their research will be helpful in studying the teacher-student relationship in humans. 

Click here to see more about what's going on at the CHCI


or.gif (8512 bytes)The Orang Utan Language Project

At the National Zoo, Orang utans are learning to communicate in a language designed especially for them.  Their training began with flash cards and has advanced to the use of computers with touch screens.  Both nouns and verbs are being taught with the goal of eventually testing the Orang utans ability to develop syntactically accurate sentences.  The Orang utan Language Project operates under the idea that the orang utans will learn the language if they wish to use it to communicate with their trainers and to control their environment.  As such, no coercion is used in teaching the language.

Click here to learn more about what the orang utans are learning at the National Zoo and to try learning a little symbolic language yourself.

Click here to read a transcript of an on-line conversation with Koko the gorilla
            -What does this interview really suggest about primate language ability?