DECEMBER 14, 2009

American Sign Language Development and Learning in Apes

The scientific community has vastly studied primate evolution. Anthropologists have particularly been interested in the evolution of language in primates and how it applies to human culture. The acquisition of the American Sign Language by primates as a form of communication has been viewed as a catalyst by anthropologists seeking to find out how language originated in the early man. The study of the use of language in primates has focused on orangutans, chimpanzees, bonobos and gorillas. Due to the inability of primates to produce vocal sounds, these studies have focused on the use of; computer keyboards, lexigrams, plastic tokens and the American Sign Language.

Scientists have debated on the definition of language and its distinction from speech. While previous definitions of humans were merely based on their unique ability to communicate using language, these definitions has been criticized by the fact that primates have been able to acquire and use language as a means of communication. Charles Hockett maintained that in order for any system of communication to qualify as a language it has to have several properties. These include the ability for; interchangeability, specialization, duality and productiveness. Language must also be displaceable, culturally transmittable and must include the property of arbitrariness[1] .

The studies on the use of language by primates have mainly focused on American Sign Language. Successful use of language has been demonstrated by extensive use of symbols, grammar and the ability to articulate real and new situations using the language[2].

Studies which focused on primates in the wild depicted various methods of communication. These studies have indicated that primates use; olfactory, visual, vocal and tactile communication based on the environmental and the social context[3]. Sue Savage-Rumbaugh, who maintains that there is need for more research on primate communication especially in the wild, focused on studying the complexity of chimpanzee communication both in the wild and within controlled settings[4] .

The question of use of language in apes was first highlighted by Samuel Pepys in 1661, who speculated that a primate he had observed in the wild could be taught how to form signs and speak[5]. Although there were no immediate follow up studies, Julien Mettrie published a documentary in 1748 which also focused on the possibility of teaching apes how to speak[6]. The first actual studies on ape language were conducted in the first half of the twentieth century and specifically focused on teaching apes how to speak.

Robert Yerkes who was a pioneer in this field extensively attempted to teach chimpanzees how to speak during the 1920s’. Yerkes concluded that apes could not learn speech because they lacked the ability to imitate sound[7]. This was later attributed to the different vocal habits in primates and the absence of speech organs. Yerkes however suggested teaching primates sign language instead. This recommendation was not followed up until the 1960s’ when Sue Savage-Rumbaugh trained Washoe.

In the meantime other researchers attempted to teach primates how to speak. Keith and Cathy Hayes recorded the most significant success after they reported that they had successfully taught a Chimpanzee called Vick how to speak. Vickis’ vocabulary was only four words but was a significant success[8]. Other researchers however observed that though primates could not use speech as a means of communication they easily learnt how to use gestures extensively to communicate and they also seemed to understand the human language[9].

The scientific community has focused on the use of sign language by primates as a means of conveying observations, emotions and thoughts. Chimpanzees and gorillas have reported the most success in acquiring and using sign language as depicted by the two case studies of Washoe, a chimpanzee who was able to acquire and use two hundred and fifty different signs and Koko a gorilla who was able to successfully use one thousand different signs.


Washoe is the first recorded successful study on the use of American Sign Language in primates. Washoe was a Chimpanzee who was adopted by Allen and Beatrix Gardner who started teaching her sign language as an infant in 1966[10].

Washoe was exposed to sign language as the only mode of communication from ten months old by all her trainers and guardians. Since chimpanzee infants remain dependent on the mother for up to two years, Allen and Beatrice Gardener were still able to influence language development. The environment was simulated to closely resemble that of a deaf human infant. The Gardeners’ used instrumental conditioning to motivate learning[11]

Washoe learnt how to use sign language through imitation, sign babbling, transfer and combinations. Within a short period Washoe was able to transfer learnt signals to accompany various referents. The Gardners’ recorded that Washoe was able to apply the word ‘more’ into other referents apart from the original referent which was tickling[12]. Washoe was also able to transfer the dog sign to indicate barking even when she could not see the dog.

Washoe was able to combine learnt signs to articulate a situation[13]. Differentiation was depicted by the ability to acquire and use specific signs to replace general signs. Initially Washoe experienced difficulty differentiating the word ‘flower’ from ‘smell’. After some training she was able to learn the sign for flower and differentiate it from that used to signal smell[14]


The most successful observation on Washoe was made when she adopted a Chimpanzee called Loulis. One of the most important standards used to define language is the ability for cultural transmission[15]. Although Loulis was not exposed to any sign language from humans, a study on her which was conducted five years after the adoption by Washoe indicated that Loulis had already learnt more than fifty signs from association with the other apes.

Bob Ingersroll who was among the researchers who studied Washoe and Loulis concluded that there was no active learning between Loulis and the other apes. He suggested that Loulis picked up the use of sign language from observing the other apes as they used signs to communicate[16] . This depicted sign language among the primates as a self supporting robust system unlike keyboards and the use of plastic tokens as a form of communication.


Nim was a male chimpanzee who was studied by Herbert Terrace in an attempt to discredit the published findings on the successful use of sign language by Washoe, Lana and Sara. Terrace had earlier discredited these findings comparing the observations to the phenomenon of teaching pigeons how to sort beads based on different color. Terrace also criticized the use of operant conditioning and a rewarding system, arguing that the primates would not use sign language in the absence of rewards.[17]

Terrence argued that apes only used signs so as to receive rewards from the trainers. Terrace exempted the use of tangible rewards in his study and used verbal approval as the only form of motivation[18]. Apart from this deviation, Terrace attempted to replicate the methodology used by the Gardners’ to teach Washoe how to use sign language. He also replicated the environment used by the Gardners’.

Nim was able to use signs with other referents as had been observed in the case of Washoe. Terence observed that Nim used the sign for dirty to indicate he wanted to go to the toilet and the sign for sleep when he wanted to display boredom. This confirmed the issue of transfer in language[19].

In his definition of language Hockett stressed on the need for substitution in a language. Nim used the signs for indicating ‘bite’ and ‘angry’ to warn his audience when he was angry. He however did not bite if he was given an indication that his message was conveyed[20]. This highlighted Hocketts’ language standard of specialization.

Terence however concluded that though Nim was able to acquire an extensive range of vocabulary he could not combine words to form meaningful sentences on his own. Terrence maintained that any sentences Nim formed were prompted by observing his trainers and not as a result of independent thought[21].

Koko the Gorilla

Sign language has also been successfully taught to a gorilla. Koko is a gorilla who was raised by Francine Patterson. Koko was adopted by Patterson in 1972 and taught how to use the America sign language[22].

Koko exhibited a wider range of vocabulary than Nim, more creativity and better application of structure in communication[23]. Researchers recorded a higher level of comprehension when Koko was able to apply sign language to joke and rhyme. Koko attached a long tube to her nose and joked that she was an elephant and that the tube was her trunk[24].

The use of sign language to communicate what had not been taught depicted productivity. Koko was taught sign language by use of operant conditioning. Although researchers have debated against the use of reinforcement and suggested that the withdrawal of rewards will lead to behavior extinctions, follow up studies have indicated continued use of sign language as a form of communication even in the absence of gratification[25].

Koko has depicted remarkable success in the application of signs to explain new phenomena. William Shatner recorded that Koko was able to combine two familiar words; water and bird to describe a duck the first time she saw one. In 1998, an online chat between Koko and Paterson highlighted the fact that Koko could form sentences when she tried to request for a treat from Paterson. Patterson also reported that a male gorilla known as Michel was also able to learn the use of sign language from observing and interacting with Koko. Michel learnt six hundred signs before he died.


Kanzi, a bonobo was adopted and trained by Sue Savage-Rumbaugh. Researchers believe that Kanzi understands more human language than any other primate or non human being. He depicted a faster rate of learning than all the other apes studied before.

Kanzi learnt his words just from watching Sue Savage-Rumbaugh teach his mother how to use a lexigram[26]. A lexigram is a board consisting of symbols which are connected to the computer. By choosing symbols on a board, the computer produces a vocal simulation of the chosen symbol facilitating the primates’ understanding of the human language. Kanzi had acquired a vocabulary of more than two hundred words by the time he was six years old.

While his mother unsuccessfully received structured learning, Kanzi was taught different signs while walking through the forest. The success in teaching Kanzi sign language has been widely attributed to the change in the learning environment.[27]

Kanzi has depicted an incredible ability to construct and use sentences to communicate. This successful display of structure in his utterances depicts duality which is one of the characteristics laid out by Hockett in defining language. Kanzi has also depicted an ability to formulate his own rules in sentence construction by combining the use of a lexigram and a gesture to indicate an action and a following agent[28].

Kanzi has demonstrated an incredible ability to identify, name objects and construct sentences outside the specific contextual cues. In a study where he was asked to identify thirty five objects in one hundred and eighty trials, he depicted a 93% success rate[29]. Kanzi has also depicted an ability to learn verbal words. Savage-Rumbaugh observed Kanzi utter a meaningful word consistently to his sister[30].


Chantek is an orangutan who was taught how to use the American Sign Language. Chantek, who understands both the English language and the American Sign Language, has successfully learnt more than one hundred and fifty different signs. He uses these signs spontaneously while communicating without any indication of undue repetition[31].

Chantek is the first primate to indicate the internalization of a value system. Researchers have observed that Chantek has successfully internalized a simple value system consisting of the symbols for good and bad[32]. Chantek is able to use either of these symbols in their right context.

Other studies by Savage-Rumbaugh have focused on Austin and Sherman, who are two chimpanzees who were able to successfully communicate information to each other through the use of symbols. Austin and Sherman were able to use signs to communicate information which they could not communicate without using symbols[33].

The Gardners’ replicated the study on Washoe using other chimpanzees. These included; Moja, Dar, Pili and Tatu. They observed the same tendencies and concluded that sign language was easily learnt and transferred by primates as a form of communication. The Gardners’ also observed that these primates would sign to each other, dogs, cats and even to humans. They also signed to inanimate objects including trees and toys[34].

Several researchers have argued against the ability of primates to use language. These critics include renowned linguist Noam Chomsky who proposed the universal grammar theory which strictly defines language as a human skill. Steven Pinker has also argued against the use of language by primates by ascribing the recorded observations to the ability of apes to acquire trained behavioral responses in an attempt to earn rewards. However these criticisms have been discredited using Terraces’ observations on Nim. These studies have also been characterized by various ethically based protests. Washoe and Viki distinctly characterized themselves as humans and characterized other chimpanzees as primates[35].

In conclusion the study of language acquisition in apes has shed light to the nature of cognitive and intellectual capabilities in primates as well as to the unique nature of development of the human language. The successful acquisition of the American Sign Language by the different primates continues to shed light on the process of language development in evolution and has provided several feasible avenues for teaching mentally retarded children how to communicate.

Works Cited

Cavalieri and P. Singer.1993. The Great Ape Project: Equality beyond Humanity. New York: St. Martin’s Press.

Gardner, R.A. and Gardner, B.T. 1979.Teaching Sign Language to a Chimpanzee. Baltimore: University Park Press.

Gardner, R.A. and Gardner, B.T. 1989.Teaching Sign Language to Chimpanzees. Albany: State University of New York Press.

Hewes, G.W. 1977. Language Learning by a Chimpanzee: The Lana Project. New York: Academic Press.

Linden, E. 1974. Apes, Men, and Language. New York: Saturday Review Press.

Patterson, F., and Linden, E. 1981. The Education of Koko. New York: Holt, Rinehart and Winston.

Rumbaugh, D.M. 1977. Progress in Ape Research. New York: Academic Press.

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

Savage-Rumbaugh, E.S., Rumbaugh, D.M., and Boysen, S. “Symbolic Communication between Two Chimpanzees,” Science, 201 (1978): 641-644

Savage-Rumbaugh, S. and Lewin, R. 1994. Kanzi: The Ape at the Brink of the Human Mind. New York: John Wiley & Sons.

Strum. S.C. 1987. Almost Human: A Journey into the World of Baboons. New York: Norton Press.

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

Wallman, J. 1992. Aping Language. Cambridge: Cambridge University Press.

[1] Linden, E. 1974. Apes, Men, and Language (New York: Saturday Review Press, 1974), 137.

[2] Wallman, J, Aping Language (Cambridge: Cambridge University Press, 1992), 6.

[3] Strum. S.C. Almost Human: A Journey into the World of Baboons (New York: Norton Press, 1987), 263.

[4] Savage-Rumbaugh, E.S. Ape Language: From Conditioned Response to Symbol (New York: Columbia University Press, 1986), 400.

[5] Wallman, J, Aping Language (Cambridge: Cambridge University Press, 1992), 11.

[6] Hewes, G.W. Language Learning by a Chimpanzee: The Lana Project (New York: Academic Press, 1977), 12.

[7] Rumbaugh, D.M. Progress in Ape Research (New York: Academic Press, 1977), 77.

[8] Gardner, R.A. and Gardner, B.T. Teaching Sign Language to Chimpanzees (Albany: State University of New York Press, 1989), 7.

[9] Ibid, 6.

[10] Gardner, R.A. and Gardner, B.T. Teaching Sign Language to a Chimpanzee (Baltimore: University Park Press, 1979), 12.

[11] Ibid, 144.

[12] Gardner, R.A. and Gardner, B.T. Teaching Sign Language to a Chimpanzee (Baltimore: University Park Press, 1979), 190.

[13] Ibid, 191.

[14] Ibid, 193.

[15] Gardner, R.A. and Gardner, B.T. Teaching Sign Language to Chimpanzees (Albany: State University of New York Press, 1989), 25.

[16] Ibid, 26.

[17] Terrace, H.S. Nim (New York: Alfred A. Knopf Publishers, 1979), 21.

[18] Ibid, 145.

[19] Ibid, 143.

[20] Ibid, 143.

[21] Terrace, H.S. Nim (New York: Alfred A. Knopf Publishers, 1979), 147.

[22] Patterson, F. & Linden, E. The Education of Koko (New York: Holt, Rinehart and Winston, 1981), 2.

[23] Ibid, 116.

[24] Ibid, 117.

[25] Ibid, 145.

[26] Savage-Rumbaugh, S. & Lewin, R. Kanzi: The Ape at the Brink of the Human Mind (New York: John Wiley & Sons, 1994), 161.

[27] Ibid, 162.

[28] Ibid, 161.

[29] Savage-Rumbaugh, S. & Lewin, R. Kanzi: The Ape at the Brink of the Human Mind (New York: John Wiley & Sons, 1994), 168.

[30] Ibid, 173.

[31] P. Cavalieri P. and Singer, P. The Great Ape Project: Equality beyond Humanity (New York: St. Martin’s Press, 1993), 47.

[32] Ibid, 52.

[33] Savage-Rumbaugh, E.S., Rumbaugh, D.M., and Boysen, S. “Symbolic Communication between Two Chimpanzees,” Science, 201 (1978): 641.

[34] Gardner, R.A. and Gardner, B.T. Teaching Sign Language to Chimpanzees (Albany: State University of New York Press, 1989), 24.

[35] Linden, E. 1974. Apes, Men, and Language (New York: Saturday Review Press, 1974), 50.