Can primates learn signs and acquire language?

In August 1969, Allen and Beatrice Gardner of the University of Nevada published an article in the journal Science claiming to have communicated with a chimpanzee called Washoe. 

She had been brought up since 1966 in the Gardner’s trailer and could use 100 signs. She was intelligent enough to sign “water bird” when she saw a swan. By the time of her death in 2007, she used 250 signs.

She could ask for things, though not with perfect grammar: “Gimme sweet, come open.”

Before this, people had tried to teach primates to talk like parrots, a bizarre choice as primates have thin tongues and high voice boxes making pronunciation very hard. No chimp had been able to pronounce more than three words (mum, dad and cup). The Gardners decided to use signs instead and it proved much more suitable. And they didn’t use isolated signs but full American Sign Language.

Washoe adopted a 10 month old chimp called Loulis. He became the first primate to learn signing from a chimp instead of a human, showing that signing could be introduced into primate culture. To ensure that it was Washoe who taught Loulis, her carers made sure they only used seven signs when they were with Loulis. He made his first sign after eight days.

She would mould his hand to sign ‘food’. She would sign ‘come’, approach him and pick him up. Eventually, she only had to sign for him to follow her. She would place a chair next to him and sign ‘chair’.

Later, he was placed with four other signing chimps. Only 5% of the signs they used were about food, 88% were about social interactions. With humans, they mainly signed for food.

Dr Catherine Hobaiter of the University of St Andrews lived with chimpanzees, studying there gestures for 15 years. She explained that very little is known about monkey gestures but that all four great apes could learn signs. She said:

“One of the most interesting aspects of ape gesture is that the way in which they use them resembles human language…quite different to most of their vocalizations. For example, ape gestures are ‘intentional’ – made to a specific recipient with a particular goal in mind, rather than ‘broadcast’ to the world in general.”

She explained how their upbringing affected their signing:

“Apes that were raised as ‘cross-fostered’ that is apes raised in human families used their signs freely with both apes and humans. Apes that were language-trained (often raised in isolation) only signed to other humans – and usually only in response to specific questions.”

Catherine made it very clear that these experiments could not be continued:

“This work is no longer done because we now understand that it is fundamentally unethical. To do this work apes were separated from their natural social groups – in the early years where they were taken from the wild it is likely that many of their family members were killed in front of them. Even for captive born apes, they were taken from their mothers at a few weeks or days old and then ‘raised as humans’ in a human household. It has been difficult – impossible in many cases – to reintroduce them to other apes when they’re older. Imagine taking a child and raising them with wolves for 10+years – they would have no idea how to be a ‘person’ later. So these apes never had children – because they had no normal or natural life.”

Washoe inspired dozens of similar experiments.

Koko became the first signing gorilla thanks to Francine ‘Penny’ Patterson. She was a western lowland gorilla who lived in a gorilla sanctuary in the Santa Cruz mountains. While Penny never claimed Koko could use ASL, she instead claimed that Koko had devised her own ‘Gorilla Sign Language’.

A chimp named Nim Chimpsky learned 125 signs by 1977. His trainer, Herbert Terrace of Columbia University, wanted to be the first to teach language to animals:

“I’m not the only one trying to teach a chimp sign language. There are others … but I hope to be the one who is going to do it right [if he  could] nail to the wall proof that a subhuman primate can acquire a syntactical competence that at least overlaps with that of man…the age-old distinctions concerning man’s uniqueness would no longer hold.”

Bob Ingersoll is a primatologist who worked with Washoe and Nim. He described how Deaf people interacted with them:

“I’ve seen actual human native signers interact with signing chimps. It was to me a very moving experience because there was clearly a recognition by both the humans and the apes that they were conversations going on. I saw one young lady a native signer actually shed tears when she realized that Washoe understood what the young lady had signed to her and Washoe had responded.”

Bob felt that the Deaf community should have been more involved:

“Finally, the actual Deaf community is being brought into this conversation which I think historically was overlooked to the disadvantage of everyone. We could and should have done this right from the start and I found it almost demeaning that the community that actually has the most knowledge of this topic were not included as equal partners right from the start. It seems to me that could have been to everyone’s advantage. My sympathies were always with the deaf community and the chimps who it seemed to me were being used as tools for science which was to me just wrong.”

While these were massive breakthroughs, no primate has ever learned sign language. No matter how many signs they learn grammar eluded them. What they learned was a lexicon to beg for things from their human carers.

Bob thought the early studies did not use the right expertise:

“They wanted sentences but didn’t study word acquisition in a meaningful way. They barely studied grammar especially ASL grammar and expected first generation learners with no evolutionary background in language to produce grammatical sentences based on spoken English. I think that was foolish and bad science and unfair to two groups. The actual ASL using community of humans and the apes themselves who were removed from their actual ape families and expected to produce a grammatically correct “language” based on what teachers with very little actual knowledge about chimps or the actual use of sign language by the human deaf community.  In second and third generation studies some of those concerns were addressed but many studies were one and done so to speak which to me was unfair and inadequate.”

Koko could sign “You key there me cookie” when presented with a locked biscuit tin. So while she understood the nouns ‘key’ and ‘cookie’, she had no idea what order they should be in. There are 120 combinations of those five words, none of them grammatically correct. Even her grasp of the word ‘cookie’ was doubtful as she would use it for generic sweet foods.

Nim would usually sign “Banana me” but it was not always clear whether he was asking for a banana or claiming possession of one because he could not tell ‘me’ and ‘mine’ apart. A quarter of the time he would sign ‘Me banana’ instead.

By 1979, Terrace had videoed 20,000 examples of Nim signing and had come to the conclusion that Nim had not grasped the concept of grammar:

“Much  of  the  apes’  behavior  is  pure  drill…Language  still  stands  as  an  important definition  of  the  human  species.”

He noticed that Nim’s sentences were not getting longer, no matter how many signs he learned. This is in marked contrast to children whose sentences get longer as their vocabulary expands. Only a handful of the tasks these apes were being asked to do were dependent on grammatical word order and of those that were, the apes only understood them c.30% of the time.

Dr.  Clive Wynne, a psychology professor at the University of Florida, summarised the results of these experiments in “Aping Language a skeptical analysis of the evidence for nonhuman primate language.”

He said: “Moments like this tell us that Descartes was right, there really are no beasts, no matter how fortunately circumstanced, that can make known their thoughts through language. Next time you see Kanzi [a bonobo taught to use a symbolic keyboard] or one of his kind on a television documentary, turn down the sound so you can just watch what he is doing without interpretation from the ape’s trainers. See if that really appears to be language. Somewhere in the history of our kind there must have been the first beings who could rearrange tokens to create new meanings, to distinguish Me Banana from Banana Me. But the evidence from many years of training apes to press buttons or sign in ASL, is that this must have happened sometime after we split off from chimps, bonobos, and gorillas. Since then we have been talking to ourselves.”

So in conclusion; apes can learn hundreds of signs, string them together and teach them to their offspring. But what they cannot do is grasp the rules of grammar and create their own language.

This should not dispirit us though, thanks to sign language we can communicate with apes far more than we could by teaching them speech.

Edmund West is an autistic freelance journalist who has been writing articles since 2007. He also works with Autistic adults and has an MA in history. He has written for several magazines: Press Gazette, Wired, Military History Monthly, History Today, etc.