Teaching Sign Language to a Chimpanzee.

R.A Gardner and B.T. Gardner (1969).

Preliminary Considerations

The Chimpanzee as a subject.

A chimp chosen for this study because it is an intelligent and social animal. The main disadvantage of using a chimp is that it does not possess vocal apparatus that would allow the production of human speech. Hayes and Hayes (1951) tried this; their chimp, 'Vicki', produced only four sounds in six years! Chimps do use their hands a lot in their natural habitat, so it was decided to build upon this natural ability by training the author's chimp, 'Washoe', to use American Sign Language (ASL).

American Sign Language.

Each symbol will vary in its degree of abstraction (e.g. sign for 'flower' involves putting fingertips together and touching both nostrils. This is iconic, as the sign mimes a flower being held to the nose. Other signs are quite abstract, for example 'dog' is signed by slapping the thigh!). The performance of Washoe can be compared with that of deaf children.


Caught in the wild and received by the Gardners when she was between 8 and 14 months. Chimps are completely dependent until two years of age, and semi-dependent until the age of four. Full adult growth is reached between 12 and 16 years.

Laboratory conditions.

The Gardeners tried to make Washoe's environment as similar as possible to a [deaf] human infant. Many helpers were used. There was always somebody in attendance during Washoe's waking hours. Every helper communicated with Washoe by using ASL, rather than with the spoken voice (the use of which was minimised). Helper's acted as friends and companions to Washoe, making use of various games and activities to make the learning experience enjoyable.

Training Methods.


As with chimpanzees in general, Washoe naturally imitated. Washoe signed the sign for 'toothbrush' spontaneously upon entering the Gardener's bathroom and noticing toothbrushes. There seems to have been no obvious motive, except to communicate.


'Babbling' here does not mean vocal babbling, rather the untaught signs used by Washoe to communicate a desire. Washoe used a begging gesture, which was not too different from the ASL signs for 'give me' and 'come'.

Instrumental conditioning.

Humans could not learn a language, purely by instrumental conditioning, although it seems likely that the 'trick vocabulary' of early childhood could be acquired in this way. Instrumental conditioning was one strategy used with Washoe. Tickling was used as a reward. The sign for 'more' was learnt by instrumental conditioning. This sign was later applied to a variety of relevant situations.



A Sign was added to a checklist when reported by three independent observers. The sign had to occur in an appropriate context and without prompting. The checklist was used to record the frequency of a sign. A sign had to be used at least once a day for 15 consecutive days, before it was deemed to have been acquired. Alternatively a sign had to be used at least 15 days out of 30 consecutive days. By the end of the 22nd month of the project, thirty-four signs had been learnt.


The sign 'more' used in many different situations until a more specific sign had been learnt. The sign for 'flower' used inappropriately for the idea of 'smell'. After additional training eventually Washoe was able to differentiate between 'smell' and 'flower'.


Although the same object was presented for each learning trial (e.g. the same hat), Washoe was able to use the sign for other similar objects (e.g. other hats).


Washoe was able to combine two or three signs in an original way, examples being 'gimme tickle', 'open food drink' (meaning 'open the fridge'), 'please open hurry', etc.

Concluding observations.

We can not be certain that Washoe has acquired 'language'. This is because it is difficult to draw the line between what counts as 'possessing a language' and 'not possessing a language'. If Washoe were to communicate information to an observer, whom had no other source of information, then this would be strong evidence to support the claim that Washoe possesses 'language'.


It is not just the setting up of valid dependent variables that are important, perhaps what is more important, is the interpretation of the dependent variables. Does Washoe's use of signs constitute language? Chomsky (1957) believed that language is unique to humans, claiming that we have a Language Acquisition Device that enables us to appreciate readily the grammatical structure of language, enabling the infant to make sense of what would otherwise be a chaotic mass of sound. Although the chimpanzee's vocal apparatus can not produce speech sounds, this does not mean that the animal can not communicate effectively non-orally. Premack (1971) used plastic shapes. Savage-Rumbaugh et al (1980) used a special computer that produced geometric shapes that represented words. Others have used ASL (e.g. Patterson 1978 taught a gorilla, Terrace 1979 taught a male chimp. In all these cases it has to be decided whether the animal concerned possesses language. Aitchison (1983) proposes these 10 criteria for language:

  1. Use of the Vocal-Auditory Channel
  2. Arbitrariness (use of neutral symbols (i.e. words) to denote objects, etc.)
  3. Semanticity (the use of symbols to mean or to refer to objects/actions)
  4. Cultural transmission (handing down from generation to generation)
  5. spontaneous usage
  6. turn-taking
  7. Duality (a combination of different sounds and the order in which these sounds are placed)
  8. Displacement (references to things not present in time or space)
  9. Structure-dependence (e.g. the structure of grammar and the relevance of word order)
  10. Creativity


An argument that we meet when considering the work of Piaget is relevant here. The Discontinuity theory of language considers the differences between human and animal language as qualitatively different, rather than quantitatively different.


  1. Washoe demonstrates semanticity (e.g. 132 signs learnt, able to generalise). There is some evidence of displacement (e.g. 'all gone cup' and 'more milk'). Washoe combined words showing evidence of creativity. Regarding structure-dependence, Washoe was not always consistent with word order. This could be due to one or more of the following reasons:

    a) the Gardeners rewarding Washoe for correct sign production regardless of order,

    b) sign order is not as consistent as word order, this is evidenced by deaf people, who also produce signs in an inconsistent order,

    c) this was an intermediate stage,

    d) Washoe could not understand the importance of the correct ordering of the signs she was producing.
  2. Sarah and Lana were trained to use symbol order correctly and coped to a limited extent. Koko did not use any particular order. Nim Chimpsky preferred certain sign orders, but failed to demonstrate that he understood any rules.
  3. Petitto and Seidenberg (1979) conclude that apes use repetitive, inconsistently structured strings. Nim's longest recorded utterance is 'Eat drink, eat drink, eat Nim, eat Nim, drink eat, drink eat, Nim eat, Nim eat, me eat, me eat'.
  4. We must question whether the apes demonstrated true semanticity. Are they really using the signs as words? Also, are the apes being spontaneous? Chimps try to 'acquire' objects rather than idly converse about them.
  5. Children can understand that 'dog chase cat' has a different meaning from 'cat chase dog', unlike apes. We could compare the Mean Length of Utterance (MLU) for children with the MLU for apes. This comparison would be misleading owing to the repetitive nature of the strings created by apes. Ignoring this, children quickly move from a MLU of 11/2 to a MLU of 4 words. Nim's MLU did not rise, holding steady at around 1.1 to 1.6. Nim did not sign spontaneously on his own initiative. Trainer prompted most signings. Nim would often start to sign before the trainer had finished signing; this suggests that he is not having a genuine conversation.
  6. Gardener's attack Terrace's upbringing of Nim, saying that he was subjected to routine drills rather than being brought up as a child would be.
  7. Eysenck (1984) points out that the Gardners concentrated on only one component of an ASL sign, that being just the hand configuration. Movement, orientation and location were neglected. ASL does not have the grammatical structure of English, so we should be careful about equating signing ASL with speaking a language. Nonetheless, deaf people are using ASL as a language, so we should accept that if a chimp uses ASL then he or she is using a language also. Brown (1986) suggests the chimp should use ASL in such a fashion that would convince us that a human had the capacity to use ASL. However, we must be wary of anthropomorphizing (viewing animal behaviour as if it were acting as a human).
  8. Chomsky (1980) believes that apes lack the capacity to understand the 'rudiments of the computational structure of human language'. Aitchison (1983) believes that the relative ease at which humans acquire language point to an innate ability. Eysenck (1984) believes that language in its complete form is unique to humans.
  9. Savage-Rumbaugh believes that the difference between human and chimp language is quantitative. She trained bonobo chimps to use a 'lexigram', in a naturalistic setting. This consisted of a portable board that could be carried to wherever the chimps were, and used regardless of whatever they were doing. Each time a geometric shape on the board was pressed a word would sound. The board was used to allow the chimp to communicate in much the same way as a child would use spoken language. The board was used successfully, with the chimps displaying relative ease of learning the symbols, and by their using the symbols spontaneously.
  10. The Gardners didn't see Washoe for 11 years, yet when she saw them Washoe immediately signed 'Come, Mrs G.', and led her to an adjoining room and began to play a game with her. Can we justify taking an animal away from its natural surroundings? Should we try to teach them an unnatural language? We should consider the possible psychological damage that might be caused by all of this teaching. The Great Ape Project, supported by eminent people, believes that apes should have many of the rights of humans.


  1. What is anthropomorphism? [2 marks]
  2. Give two other methods used by other chimps as alternatives to signing. [2 marks]
  3. What is the differences between the chimp's and the children's use of language? [8 marks]
  4. Can apes acquire language? [7 marks]
  5. Discuss the programme of teaching language to chimps from an ethical standpoint. [6 marks]


Jane Goodall's article on Chimps

Computer masters baby talk

Your questions

2) Comment on what Gardner & Gardner tells us about the human behaviour
and experience it investigated.
The development of language in the chimp parallels the development of
language in children (at least deaf children).  Chimp language just takes
longer.  The acquisition of language seems to require much interaction with
caregivers and is developed through relating language to everyday events
that are shared between the chimp and the caregivers; just as in humans!

4.Gardner and Gardner: Chimpanzee study

Finally, I was wondering if you could give me one ethical issue-apart from the issue of implications for the rights of Apes-testing, and of the removal from its natural environment. Also there was 2 other issues (not ethical) which were found within the study.





Lab chimp speaks his own language 10:15 02 January 03


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Last updated 3rd January 2003