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Language-Using Apes

J’aime Wells is an ape talking about the possibility of apes talking.

I live a few blocks away from some unusual neighbors: three chimpanzees who fluently use American Sign Language. Their names are Tatu, Dar, and Loulis, and their more famous family member Washoe was the first non-human to acquire a human language. Their home is the Chimpanzee and Human Communication Institute (CHCI), located on the campus of Central Washington University in Ellensburg, Washington. I have been a volunteer docent [public educator] there since 2007.

The language capabilities of non-human apes have been studied in several important projects, with widely different methods. In this article I will focus on Washoe and her family. I believe that these chimpanzees are genuinely using language, and that much of the philosophical resistance to this claim is based on misunderstandings of the research and its results. The misunderstandings and doubts come from at least two sources. First, some philosophers and linguists defend theories which imply that only humans can learn language. However, empirical research results should be considered on their own merits, regardless of their implications for previously-held theories. Second, journalists writing for a non-academic audience often express doubt about whether Washoe’s language use has really been proven. Sometimes they assume that the results of all ape language projects must be the same. For example, Washoe is often discussed alongside another chimpanzee, Nim Chimpsky, who also participated in a research project using American Sign Language (ASL). Although the two projects were similar in some ways, the methodology of the two research teams differed significantly, as did the results. Any conclusions drawn about one specific ape language project should not be assumed to apply to other projects.

Here I will summarize some of the results of the research Washoe and her family have been involved in. Then I will briefly consider what these results might mean for the question of whether humans are hard-wired for language acquisition.

Apes and Anthropomorphizing

In terms of species category, humans and chimpanzees both belong to the family of large-bodied (or ‘great’) apes, which family also includes bonobos, gorillas, and orangutans. Within that family, chimpanzees are most closely related to bonobos. Their next closest relatives are humans. Although most of us are familiar with the idea that humans are ‘related to’ apes, the truth that we are apes can still surprise us. The notion of a clear dividing line between ‘humans’ and ‘animals’ is deeply embedded in our culture. This cultural bias makes it easier for us to believe claims that humans are special, and harder for us to admit that any other species might be similar to ourselves.

If your starting assumption is a hard division between the categories ‘humans’ and ‘(just) animals’, then attributing any human-like characteristic to ‘mere animals’ appears to be sentimental anthropomorphism. On the other hand, if we start by acknowledging the close relationship between humans and our fellow apes, then it no longer seems as surprising that other ape species might have qualities we usually consider human-like. So when discussing whether apes can learn language, it is useful to keep in mind that all the participants in the conversation – human researchers, writers, and commentators – are apes, using language.

Considering our close kinship, it is not surprising that chimpanzees are similar to humans in many ways. They use tools, including twigs for termite fishing, stone hammers and anvils for cracking nuts, and in a few observed cases, sharpened wooden spears for hunting. They also display cultural practices that are specific to particular family groups and transmitted from parent to child, including ways of making and using tools, hunting practices, and gestures used to communicate. Thus, if a clear line is to be drawn between ‘animals’ and ‘humans’, it cannot be drawn on the basis that ‘only humans are tool-users’ or ‘only humans have culture’, since chimpanzees share these qualities. Some would argue that the unique quality of humans is that we are full language-users. However, I believe that Washoe and her family have shown that chimpanzees can learn and use a human language.

Cross-Fostering Projects

Washoe acquired American Sign Language in a cross-fostering project started in 1966 when she was ten months old. Cross-fostering means that infants of one species are raised by adults of another species. In this case Washoe was raised by humans who treated her as if she was a human child. She wore diapers and clothes, ate in a high chair, played with toys, learned to brush her teeth, and was potty-trained. Her caregivers used no spoken language in her company, using only ASL to communicate with one another and with her.

Washoe learned first to babble signs to herself, then to use them properly in context. When she had acquired eight reliable signs, she began putting together two signs to form simple phrases such as COME OPEN (when the door was locked) or MORE TICKLE (when a caregiver stopped tickling her). (See ‘Development of phrases in the utterances of children and cross-fostered chimpanzees’, by her caregivers, Beatrix T. Gardner and R. Allen Gardner in The Ethological Roots of Culture, 1994.) After Washoe was shown to have success at acquiring ASL, a second cross-fostering project began in 1972, in which several infant chimpanzees were raised together as siblings. Tatu and Dar, two of the current residents of CHCI, participated in this study. Not only did these chimpanzees acquire signs, as Washoe had, they also used the signs to communicate with each other, not just with their human caregivers.

As Washoe became an adult, the research team wondered whether she would teach the signs she used to an infant that she was raising. Loulis became Washoe’s ‘adopted son’ in 1979. At that time, the humans restricted the ASL signs they used around Washoe and Loulis to a short list of seven: WHICH, WHAT, WANT, WHERE, WHO, SIGN, and NAME. The idea was that if Loulis was observed using any signs not on this short list, the researchers would know that he had learned them from Washoe.

Loulis was observed making his first sign after only 8 days with Washoe. It was the name sign of one of the caregivers, and not one of the seven signs he had seen humans using. After eighteen months, he had learned nearly two dozen signs. (Further discussion of the three projects I mentioned can be found in Next of Kin: My Conversations with Chimpanzees, by Roger Fouts with Stephen Tukel Mills, 1997.)

Washoe passed away in 2007 at the age of 42, but Loulis, Dar and Tatu still live at CHCI.

Signs of Language

Philosophers have different definitions of language, and thus different criteria for when an observed phenomenon counts as language use. Here I put forward the points I think are most relevant to showing that Washoe and her family are genuinely using language. The first three will be discussed together:

1) The chimpanzees sign even when they are not prompted by a human (even unconsciously).

2) The chimpanzees talk about a variety of subjects, including describing their surroundings and initiating games. Their sign use does not primarily consist of begging for food.

3) The chimpanzees’ signs are understandable and recognizable to independent observers who are fluent in ASL.

A claim sometimes made is that the chimpanzees do not really understand the signs they are making, but have simply learned to give the human researchers specific signs in response to specific cues, like a horse or dog that has learned to do a trick on command. To counter such claims, several research projects have been carried out to show that Washoe and her family are not using signs solely based on human prompting.

At the age of four, Washoe was tested in a double-blind study designed to eliminate the possibility of unconscious cueing from humans. She was asked to identify either an object in a cabinet or an image on a slide. The researcher signing to Washoe and recording her responses could not see the object or image, and did not know what the correct answer was. An answer was counted correct only if two independent human observers agreed on what she had signed (see Next of Kin, pp.98-101.)

Young Washoe did very well on these tests. In a test of 64 trials, she scored 86% correct. Researchers found that rewarding her with treats such as raisins ended up harming her performance, since she became more interested in signing RAISINS than in answering the test questions! But when rewards were not given, Washoe became more focused on the game for its own sake, and more likely to correctly name the object or image.

Later research performed between 1983 and 1985 used remotely-controlled cameras to capture chimpanzee-to-chimpanzee conversations among Washoe and her family. Twenty minute segments of video were recorded, three times a day, at random hours. No humans were present while the cameras were recording.

The first fifteen hours of tape captured more than two hundred examples of chimpanzee-to-chimpanzee signing. These tapes were shown to independent observers who were fluent in ASL. Nine out of ten times, the observers agreed on the meaning of the chimpanzees’ recorded conversations. (Next of Kin, pp.302-304)

In total, the study captured and classified over 5,200 chimpanzee-to-chimpanzee interactions, all of which occurred with no humans present. Over 88% of these conversations were categorized as play, social interaction, and reassurance. For example, the sign CHASE was frequently used to initiate a game, and the sign HUG/LOVE to reassure. The remaining 12% of conversations fell into the categories of food, grooming, signing to self, cleaning, and discipline. Food alone accounted for only about 5% of the conversations. (See ‘Chimpanzees’ use of sign language’, by Roger S. Fouts and Deborah H. Fouts, www.animal-rights-library.com/texts-m/fouts01.htm)

4) The chimpanzees use signs creatively and in new contexts.

Washoe began to use her signs in new contexts very early. For example, she learned the sign OPEN from caregivers, who signed it as they opened the door to take her out into the yard. After she understood it, they would wait for her to ask before opening the door. Then Washoe herself moved the sign to a new context, requesting that caregivers OPEN a briefcase. Later, she asked for a drink of water by signing OPEN on the water faucet, something she had never seen a human caregiver do (cf ‘Evidence for sentence constituents in the early utterances of child and chimpanzee’, Gardner and Gardner, Journal of Experimental Psychology: General, 1975, Vol.104, No.3).

A 1989 research project on imaginary play found instances of several types of creative use of signs by Washoe and her family. For example, the chimpanzees occasionally treated toys as if they were alive, as when Dar signed PEEKABOO to a teddy bear. A chimpanzee may also pretend that an object is something else, as when Loulis put a block of wood on his head and signed HAT (Fouts and Fouts again).

5) The chimpanzees can combine signs in original ways, creating new phrases and sentences.

Washoe began inventing names for objects at a young age. Although her caregivers referred to the refrigerator as COLD BOX, she called it OPEN FOOD DRINK. She was taught the name POTTY CHAIR for her toilet, but she invented the name DIRTY GOOD. Similarly, when introduced to chives, Tatu invented a name for them by combining two familiar signs: ONION GRASS.

The kinds of phrases used by the young chimpanzees roughly paralleled the phrase use of young children: they learned phrase patterns like ‘verb + object’ and then used that pattern to generate new phrases. For example, GROOM DAR and CHASE SUSAN are both verb + object phrases. (Gardner and Gardner, in The Ethological Roots of Culture.)

6) The chimpanzees understand and use correct ASL grammar, which relies on inflection and facial expressions.

The grammar of ASL is not the same as English grammar. Word-for-word transcriptions of ASL into English can sound misleadingly like baby talk. For example, ASL does not include the verb ‘to be’ or articles like ‘the’. Word order is far more important to English than sign order is to ASL. However, ASL is not a childish or primitive version of English: it is a distinct language in its own right. ASL relies on inflections and facial expressions to convey part of the meaning of the signs. For example, signing GO with raised eyebrows indicates a question, such as ‘Should we go?’ while the same sign with a different facial expression could indicate a command. Signing HELP with no inflection might be ambiguous, but moving the sign towards a person clarifies the meaning as ‘Help her’.

The chimpanzees have a strong grasp of the importance of facial expressions and inflections, and use them similarly to human signers. There is also evidence that chimpanzees understand semantic categories. For example, it has been observed that their answers to ‘Wh’ questions (Who, What, Where, Why and When) are likely to be in the correct semantic category even when the answer is factually mistaken. For example, they answer ‘Who’ questions with names, and ‘Where’ questions with locations. (Gardner and Gardner, Journal of Experimental Psychology: General, 104, 3.)

A Language Module In The Brain?

One of the major philosophical theories affected by this evidence from non-human language research is the theory that language ability is innate.

Imagine that you have enrolled in a course to start to learn a foreign language. In these classes, no one will explain the rules of grammar to you or translate vocabulary into English. Instead, native speakers will talk to you and to each other only in the language. They may slow down their speech, or repeat sentences you don’t understand, or they may not. You are free to try speaking the language whenever you feel ready. The native speakers may sometimes correct any mistakes you have made; at other times you may have very little indication of whether your speech is correct or not.

Learning a language in this class would seem to be nearly impossible: and yet this task is routinely accomplished by toddlers. Small children quickly learn to speak the language in which they are immersed. They internalize rules of syntax even though no adult explains these rules to them. Adults may or may not correct grammatical mistakes. It seems unbelievable that under these messy, confusing conditions, any child could figure out how to construct understandable sentences. Yet nearly all children do succeed in mastering their native languages, including using rules of grammar to make new sentences that no one has said to them before. This has often struck philosophers (and parents) as a remarkable feat.

Nativism is a theory intended to explain the remarkable success children have at learning language. Nativists hold that we are born with a specialized mental facility for learning language. This facility is sometimes referred to by philosophers as a language ‘organ’ or ‘module’ within the brain. This module would have universal, underlying rules of syntax hard-wired in (meaning, installed when the brain is being formed). Of course, the particular language a child learns depends on her environment. When a person is exposed to a particular language, the module can identify and apply the rules of syntax specific to that language.

Linguist Noam Chomsky is perhaps the most famous proponent of the idea that language use depends on an innate or inborn facility. Chomsky maintains that only human brains have the language-acquisition area. This, he says, explains why only humans can learn and use language. Conversely, if it turns out that non-humans can learn a language, that would imply that language ability does not depend on a language module possessed only by humans.

Chimpanzee brains are fairly similar to human brains, of course. If human brains have a special language-acquisition area, one might suggest that chimpanzee brains have an analogous area, accounting for their ability to acquire language under the right circumstances. But if that’s so, why have chimpanzees not developed their own language? To quote Chomsky: “if apes have this fantastic [linguistic] capacity, surely a major component of humans’ extraordinary biological success (in the technical sense), then how come they haven’t used it? It’s as if humans can really fly, but won’t know it until some trainer comes along to teach them.” (Interview entitled ‘On the Myth of Ape Language’, available at www.chomsky.info.) Chimpanzees in the wild do have methods to communicate, via gesture and vocalization, but it does not appear that those methods constitute a full language. Chimpanzees have actually acquired language only under specialized conditions, with humans serving as teachers and models of language use.

The argument for the existence of a language module in the brain is that it is the only possible explanation for the ability of human children to learn a language. But if chimpanzees can learn a language even though they don’t have the language module, clearly the module is not the only possible explanation for linguistic ability. Conversely, someone who holds that language can only be learned by beings with language modules in their brains must, for the reason Chomsky gave, deny that chimpanzees can learn language.

Who Is A Language User?

I’ve tried to put forward some of the evidence that Washoe’s family are genuinely using language. Of course there may be some criteria as to what counts as language use which I have not addressed here. However, the approach taken by researchers studying this family has often been to compare the sign acquisition by the young chimpanzees to the language acquisition of young humans. The chimpanzees were found to develop their language use in similar ways to children, although not at the same rate. In devising criteria for what counts as language use, we should be careful not to make the rules so stringent that we must deny that human four-year-olds are language users.

We tend to set up the question as an all-or-nothing, Yes/No question: Can a species use language or not? This may not be the most productive way to think about the issue. There are different ways and levels to use language, depending on whether the speaker is a toddler, a poet, or a philosophy professor.

If we think in terms of a continuum from lesser to greater language ability, does that mean we must give up the idea that we are born with a language module? In principle, there is no reason why a species couldn’t have an innate ability that was not used. An individual human would not develop language if he or she was never exposed to one. But humanity did develop language without any teachers, while the chimpanzee species apparently has not. Perhaps we could postulate a slightly different, less well-developed, less efficient language module in chimpanzee brains. Consider: at some point in our evolution, did the innate language bit of the brain pop suddenly into existence, or did it also evolve? If it evolved, there will have been a less efficient version at some point in our species’ history – perhaps possessed by the last common ancestor of chimpanzees and humans.

If we move towards thinking of language use as a matter of degree, it is not clear whether the idea of a dedicated language module is still useful. We may instead choose to talk about general intellectual abilities which can be used for language acquisition as well as for other kinds of learning and adaptation. In either case, the theorist who wants to argue that Washoe’s family are not genuinely using language must pose specific challenges to this idea. It is no longer reasonable to dismiss their linguistic ability with a wave of the hand.

© Dr J’aime Wells 2012

J’aime Wells earned a PhD in Philosophy from Rutgers University in 2006, and is currently a freelance writer in Ellensburg, Washington.

• Tatu, Dar, and Loulis live at the Chimpanzee and Human Communication Institute. On weekends, you can attend a one-hour ‘Chimposium’, where you can learn more about the family and meet them for yourselves: www.friendsofwashoe.org.

• Thanks to the staff of CHCI for research assistance. Special gratitude goes to Lisa Lyons and Jason Wallin.

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