Great ape language

Research into non-human great ape language has involved teaching gorillas, chimpanzees, and orangutans to communicate with human beings and with each other using sign language, physical tokens, and lexigrams; see Yerkish. Primatologists argue that the primates' use of these tools indicates their ability to use "language", although this is collides with some definitions of that term.

Questions in animal language research
Animal language research attempts to answer the following questions:


 * What problems can animals solve without language, and can they solve them better after they have had language training?
 * Can the lessons learned in teaching animals be applied to human children?
 * How, and how much, do animals' abilities to learn language differ from those of humans?
 * Are the abilities that underlie language general or highly specialized?

Apes that demonstrate understanding
A production is a stream of lexemes with semantic content. A language is grammar and a set of lexemes. A sentence (or statement) is a stream of lexemes which obeys a grammar, with a beginning and an end. Non-human animals have been recorded to have produced behaviors which are consistent with meanings accorded to human sentence productions. (That is, some animals in the following species can be said to "understand" (receive), and some can "apply" (produce) consistent, appropriate, grammatical streams of communication.) David Premack and Jacques Vauclair have cited language research for the following animals:
 * Common Chimpanzees
 * Gorillas
 * Orangutans
 * Bonobos

Primate use of sign language
Sign language and computer keyboards are used in primate language research because non-human primates lack vocal cords and other human speech organs. However, primates do possess the manual dexterity required for keyboard operation.

Many researchers into animal language have presented the results of the studies described below as evidence of linguistic abilities in animals. However, it is important to note that many of their conclusions have been disputed.

Kanzi
Kanzi, a Bonobo (Pygmy Chimpanzee, Pan paniscus), is believed to understand more human language than any other nonhuman animal in the world. Kanzi apparently learned by eavesdropping on the keyboard lessons researcher Sue Savage-Rumbaugh was giving to his adoptive mother. One day, Rumbaugh used the computer to say to Kanzi, "Can you make the dog bite the snake?" It is believed Kanzi had never heard this sentence before. In answering the question, Kanzi searched among the objects present until he found a toy dog and a toy snake, put the snake in the dog's mouth, and used his thumb and finger to close the dog's mouth over the snake. In further testing beginning when he was 7 ½ years old, Kanzi was asked more than 600 complex questions, responding correctly over 74% of the time. Kanzi has been observed verbalizing a meaningful noun to his sister.

Washoe
Washoe, a Common Chimpanzee, was caught in the wild in 1966. When she was about ten months old, she was received by the husband-and-wife research team of Beatrix T. Gardner and R. Allen Gardner. Chimpanzees 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 of age. So the Gardners received her at a good age for research into language development. The Gardners tried to make Washoe's environment as similar as possible to what a human infant with deaf parents would experience. There was always a researcher or assistant in attendance during Washoe's waking hours. Every researcher communicated with Washoe by using American Sign Language, minimizing the use of the spoken voice. The researchers acted as friends and companions to Washoe, using various games to make the learning as exciting as possible. The Gardners used many different training methods:
 * Imitation: After Washoe had learned a couple of words, she started, like chimpanzees usually do, to imitate naturally. For example, when she entered the Gardners' bathroom, she spontaneously made the sign for "toothbrush," simply because she saw one.
 * Babbling: In this case, "babbling" does not mean vocal babbling. Instead, Washoe used untaught signs to express a desire. She used a begging gesture, which was not much different from the ASL signs "give me" and "come." (Human infants who are learning sign language often babble with their hands.)
 * Instrumental Conditioning: The researchers used instrumental conditioning strategies with Washoe. For example, they taught the word "more" by using tickling as a reward. This technique was later applied to a variety of relevant situations.

The results of the Gardners' efforts were as follows:
 * Vocabulary: When a sign was reported by three independent observers, it was added to a checklist. 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 learned.
 * Differentiation: Washoe used the sign "more" in many different situations until a more specific sign had been learned. At one point, she used the sign for "flower" to express the idea of "smell." After additional training, Washoe was eventually able to differentiate between "smell" and "flower."
 * Transfer: Although the same object was presented for each learning trial (a specific hat, for example), Washoe was able to use the sign for other similar objects (e.g. other hats).
 * Combinations: Washoe was able to combine two or three signs in an original way. For example, "open food drink" meant "open the fridge" and "please open hurry" meant "please open it quickly."

Nim Chimpsky
Linguistic critics challenged the animal trainers to demonstrate that Washoe was actually using language and not symbols. The null hypothesis was that the Gardners were using conditioning to teach the chimpanzee to use hand formations in certain contexts to create desirable outcomes, and that they had not learned the same linguistic rules that humans innately learn.

In response to this challenge, the chimpanzee Nim Chimpsky was taught to communicate using sign language in studies led by Herbert S. Terrace. In 44 months Nim Chimpsky learned 125 signs. However, linguistic analysis of Nim's communications demonstrated that Nim's use was symbolic, and lacked grammar, or rules, of the kind that humans use in communicating via language. This constitutes a chimpanzee vocabulary learning rate of roughly 0.1 words per day. Compare this to the average college-educated English speaker with a vocabulary of greater than 100,000 words; humans learn roughly 14 words per day between ages 2 and 22.

Plastic tokens
Sarah and two other chimpanzees, Elizabeth and Peony, in the research programs of David Premack, demonstrated the ability to produce streams of token selections. The selections came from a vocabulary of several dozen plastic tokens; it took each of the chimpanzees hundreds of trials to reliably associate a token with a referent, such as an apple or banana. The tokens were chosen to be completely different in appearance from the referents. After learning these protocols, Sarah was then able to associate other tokens with consistent behaviors, such as negation, name-of, and if-then. The plastic tokens were placed on a magnetic slate, within a rectangular frame in a line. The tokens had to be selected and placed in a consistent order (a grammar) in order for the trainers to reward the chimpanzees.

One other chimpanzee, Gussie, was trained along with Sarah but failed to learn a single word. Other chimpanzees in the projects were not trained in the use of the tokens.

A juvenile Sumatran orangutan Aazk (named after the American Association of Zookeepers) who lived at the Roeding Park Zoo (Fresno, California) was taught by Gary L. Shapiro from 1973 to 1975 how to “read & write” with plastic children’s letters, following the training techniques of David Premack. The technique of conditional discrimination was used such that the orangutan could eventually distinguish plastic letter (symbols) as representations of referents (e.g., object, actions) and “read” an increasingly longer series of symbols to obtain a referent (e.g., fruit) or “write” an increasingly longer series of symbols to request or describe a referent. While no claim of linguistic competence was made, Aazk’s performance demonstrated design features of language, many similar to those demonstrated by Premack’s chimpanzee, Sarah.

Lexigrams
Lexigrams are images on flat "keyboards", arranged in rectangular arrays. 

Criticisms of primate language research
Many scientists, including MIT linguist Noam Chomsky and cognitive scientist Steven Pinker, are skeptical about claims made for great ape language research. Among the reasons for skepticism are the differences in ease with which human beings and apes can learn language, questions as to the whether there is a clear beginning and end to the signed gestures, and whether the apes actually understand language or are simply doing a clever trick for a reward.

While vocabulary words from American Sign Language are used to train the apes, native users of ASL note that mere knowledge of ASL's vocabulary does not equate to ASL, but more closely reflects Pidgin Signed English which is not a full-fledged language. In the research involving Washoe, all researchers returned lists of signs Washoe used, with the exception of the one deaf native ASL user who reported no signs but many gestures. Native users of ASL make clear distinctions about what handshapes, palm orientations and places of articulation signs must have to constitute linguistic activity. Signs must also be used combinatorially and in the correct grammatical sequence. Thus apes are seen as attempting to approximate these complex rules but are considered to be failing because of such malformations in the production of ASL signs. (However, proponents argue that such limitations might indicate instead that great ape ASL use more closely approximates a rudimentary stage of a young child's language development, or an early stage of an adult second language learner.)