"I do believe it already understands much English; and I am of the mind it might be taught to speak or make signs." Samuel Pepys, writing in 1661 about a creature he called a "baboone", touched upon a question which still fascinates us today. Can animals be taught to communicate with people?

For many centuries, the answer was thought to be "no".

The French philosopher Rene Descartes put forward the notion that language separated humans who have souls from animals who do not and even now, the concept of language as a uniquely human attribute continues to dominate our view of animals as "dumb" creatures. Earlier this century, experiments with animal communication centered on attempts to teach speech to apes.

It is accepted by some that a chimpanzee named Viki was taught to speak four words but researchers concluded that apes were incapable of speech because of a combination of physiological factors.

Efforts then focused on teaching non-human primates to communicate using sign language. In 1966, Allen and Beatrice Gardner began teaching American Sign Language (ASL) to an infant chimpanzee named Washoe. The Gardner's claimed that Washoe acquired 132 sign words within a period of 51 months. Her development of language was compared to that of a human child. Several other chimpanzees were introduced to the project; soon they were reported to be signing to humans and to each other. Washoe and the other chimpanzees even taught her adopted infant Loulis to sign without the intervention of humans although the validity of this claim is also disputed.

In later projects, chimpanzees were taught to communicate using plastic symbols and computer-controlled-keyboards. The chimpanzee Sarah was said to recognize nouns, verbs, adjectives, pronouns, and quantifiers; she was also taught same-difference, negation, and compound sentences. Herbert Terrace's work with the chimpanzee, Nim Chimpsky, cast doubts on the capacity of apes to "acquire" ASL. Although Nim learned some words, Terrace, who had become increasingly skeptical concerning the linguistic abilities of his subject, concluded that Nim, incapable of understanding what he was signing, was merely imitating his trainer.

In 1972, Francine Patterson started work with the infant gorilla, Koko, who "acquired" 250 signs during the first 52 months of training and has become the most famous example of "interspecies" communication. In 1998, 13,000 people "questioned" Koko during an online session. Earlier this year, she was taken on a "virtual" tour of Stanford University using videoconferencing technology. Assessing ten years of work with Koko, Patterson and her partner, Ronald Cohn, reported that 876 of her signs qualified according to emitted criteria of spontaneous or appropriate use on one or more occasion. But can we accept that Koko, Washoe and co. comprehend the meanings of the signs they have been taught? Or are they merely "aping" gestures taught them in a Pavlovian reaction to stimuli such as food? Researchers like Francine Patterson claim evidence for the innovative use of language by apes like Koko including non-instrumental (not prompted by a reward), and self-directed signing. Koko's vocabulary is said to include words of her own invention such as "body-hair" and "thermometer". Claims like these are dismissed by writers like Joel Wallman who argue that not one "of the ape-language projects succeeded in instilling even a degenerate version of a human language in an ape." Much of this thorny debate centers on the definition of "language" itself.

What constitutes language is open to various interpretations but using just two criteria: performance (through the production and comprehension of speech); and competence, (in the form of abstract linguistic knowledge), it seems that non-human primates are capable of imitating "speech" after a fashion. Of course, this conclusion is fiercely disputed and there are other definitions of language apart from the one used here.

Part of the controversy over ape language projects arises from the actual language taught to the subjects. American Sign Language is as rich and as complex as a spoken language and many linguists claim that every crude gesture employed by an ape cannot be classified as "language."

The sole native signer on the Washoe Project reported: "Every time the chimp made a sign, we were supposed to write it down in the log. ... They were always complaining because my log didn't show enough signs.

All the hearing people turned in logs with long lists of signs. They always saw more signs than I did. ...

The hearing people were logging every movement the chimp made as a sign. Every time the chimp put his finger in his mouth, they'd say ŒOh, he's making the sign for DRINK,' ... When the chimp scratched himself, they'd record it as the sign for SCRATCH. ... When [the chimps] want something, they reach.

Sometimes [the trainers] would say, ŒOh, amazing, look at that, it's exactly like the ASL sign for GIVE!' It wasn't." [quoted in Steven Pinker The Language Instinct p. 337-8.]

Another aspect of the apes' use of "language" is that it lacks grammar, not as in syntactical rules, but in the way that children are able to construct meaningful sentences and to decode the meaning of sentences others make, something every human child learns without any direct instruction.

Some detractors of the ape language projects point out that the subjects are prone to merely repeating a sentence or part of a sentence the trainer had just signed.

Many of the signs are ones that are familiar to the ape and are used repetitively to convey simple desires (food, chase, friend) rather than the complex thought processes of a human child's mind.

Why should we try to teach language to apes? After all, apes (at least in their wild and natural state) appear to communicate using a far wider variety of methods than we do, including vocal (screeches, howls and grunts), olfactory (scent marking), tactile (grooming), and visual (facial expressions, posture, fur raising).

The author Douglas Adams has questioned the ethics of "this business of trying to teach apes language," suggesting that, over the millennia, we have lost the ability to speak their language.

In support of ape language projects, researchers say that they are not only exploring the nature of language itself but are also shedding light on the uniqueness of our own human ability to communicate. Another, quite different, justification for teaching language to apes is that the research would result in improved methods for training mentally retarded children who, for various reasons, fail to develop expressive linguistic skills during their early years. Most linguists argue that the special neural circuitry needed for language evolved after man's ancestors split from those of the chimps millions of years ago.

Some anthropologists, like the late Gordon Hewes, believe that spoken language evolved from gestures. Hewes argued that early man's tool-making activities might have involved a programmed series of actions, organized like syntax. Observation and recording of language acquisition in non-human primates could offer an insight into the way our ancestors might have acquired language in the past. But, as Steven Pinker argues, "an ancestral ape with nothing but hoots and grunts is unlikely to have given birth to a baby who could learn English or Kivunjo."

Pinker points out that although chimpanzees are our closest living relative, there are other, now extinct, species that were more closely related to us and from whom our ability for language probably evolved. Putting arguments over language capabilities to one side, surely it is more important that a "personality" like Koko is an eloquent ambassador for her species whatever language she is using. Dispelling their popular image as violent, repugnant creatures and raising awareness of the plight of gorillas in the wild far outweighs the significance (or not) of her language abilities.

For more information on Koko and The Gorilla Foundation, go to www.gorilla.org where teachers will find a wide range of materials suitable for use in a K-12 ESL classroom projects.