Many people believe that language is a unique capacity of
humans. Doubters of the ability of primates to use language include renowned M.I.T.
linguist Noam Chomsky and cognitive scientist Steven Pinker. Chomsky's Universal
Grammar theory clearly defines language as a skill limited to humans, the sole possessors
of the cognitive hardware which makes language possible. Chomsky makes an analogy
to flying in order to illustrate his position on primate language: "Humans can fly
about 30 feet-that's what they do in the Olympics. Is that flying? The
question is totally meaningless." Chomsky and his followers theorize that the
neural requirements for language developed in humans after the evolutionary split between
humans and primates. They base their argument on the ease with which children
acquire language in comparison to the difficulty exhibited by primates. To Chomsky
and his followers, this disparity demonstrates the presence of an innate propensity for
language in children which is not present in primates. Pinker posits the argument
that primates can be trained to do incredible things, however, these trained behaviors do
not signify language ability. He believes that the primates simply learn to press certain
buttons in order to receive rewards.
Dr. Sue Savage-Rumbaugh is a researcher who strongly
believes in the ability of primates to use language. One of her most impressive
observations involved a bonobo chimpanzee named Kanzi. Savage-Rumbaugh tried to no
avail to train Kanzi's adoptive mother to use a keyboard of symbols. The researchers
were surprised to find that Kanzi had been eavesdropping on his mother's lessons and had
acquired a substantial vocabulary. From then on, Kanzi was not given structured
training like his mother, but was taught while walking through the forest with his
trainers. By the age of 6, Kanzi had acquired a vocabulary of 200 words and was able
to construct sentences by combining words with gestures or with other words.
Kanzi's most notable accomplishment was captured on videotape: he was told, "Give the
dog a shot," and he proceeded to inject his stuffed dog with a syringe.
Savage-Rumbaugh argues that Kanzi's language was initially dependent upon contextual cues,
but that once he mastered a substantial vocabulary, he could respond accurately to 70% of
novel commands from a concealed speaker. Critics say that Kanzi's accomplishments
are not proof of language ability in primates because the crucial element in language
ability is production, not comprehension.
Observation of the vervet species of monkeys in the wild
offers support for the ability of primates to use language. The vervet monkeys have
demonstrated the most advanced primate system of communication in their natural
environment. The sounds which the vervets produce as a means of communication are
instinctive and not learned.
Sign Language
Sign language has been chosen as the superior medium in
which to conduct language instruction for primates because they are unable to vocalize
language. Some researchers hold the belief that primates are simply not intelligent
enough to speak. This theory has lost credence as further research with apes has
demonstrated their tremendous intellectual capacities in other arenas. Another
possible explanation of the inability of primates to acquire verbal language, posited by
Robert Yerkes, is that Primates are not inclined towards imitation of sounds and
therefore cannot learn verbal language. A final theory suggests that the vocal cords
of primates are not capable of supporting the production of language.
Washoe
Washoe is a chimpanzee who was taught to sign by her
caretakers, Allen and Beatrice Gardner. She was raised in a friendly environment in
which she learned sign language both through imitation and instrumental learning.
Her language acquisition was notable in several respects. Washoe was able to
transfer signs to a new referent without specific instruction. For example, she
learned the word "more" in relation to tickling but was spontaneously able to
apply the term to another referent. Additionally significant was Washoe's use of
signs in combinations after learning only about 8 or 10 signs. This spontaneous
combination of signs seems similar to the ability of human children to connect words in
sentences to which they have never specifically been exposed. Washoe has
demonstrated reliable use of 240 signs. A sign is deemed reliable when its use has
been recorded by three separate observers on 15 consecutive days. Her trainers have
observed that Washoe mostly uses her signs to discipline her children and explain her
concern about them.
...and Loulis
Washoe adopted an infant chimp named Loulis. No human
sign language was used in Loulis' presence during the first 5 years of her life.
Remarkably, Loulis nonetheless acquired more than 50 signs by watching the other
chimps. Bob Ingersoll, who studied Washoe and Loulis, observed that there was little
active teaching on the part of the adult chimps. Loulis' language acquisition thus
reflects the manner in which human children acquire language. The Gardners concluded
from Loulis' acquisition of language through observation of the other chimps that:
"once introduced, sign language is robust and self-reporting, unlike the systems that
depend on special apparatuses such as the Rumbaugh keyboards or the Premack plastic
tokens."
Nim
Herb Terrace doubted that primate language is any sort of
equivalent of human language. He did not believe that the findings of language
acquisition and use in Washoe, Loulis, and other primates were truly symbolic of language
acquisition. Instead, he theorized that there were simpler explanations for the
behaviors which had been interpreted as language use by primates (Morgan's Canon!).
Terrace posited that the primates were performing rote memorization tasks similar to
pigeons who are taught to peck at colors in specific orders. Terrace also
thought that primates only signed in order to please their trainers, not for the personal
gratification of using the signs. Terrace also says that a primate might learn to
connect a sign with food and reproduce the sign through simple conditioning, just as
Pavlov's dogs were conditioned to salivate at the sound of a bell.
Therefore, Terrace decided to conduct his own study of
primate language use. He raised a chimpanzee, Nim, as a human child and taught him
sign language in the manner in which Washoe had been taught. Nim did in fact
demonstrate some important aspects of language use. He was observed using the signs
for "angry" and "bite" to express his displeasure, an important
observation in that it demonstrates the use of arbitrary symbols to represent physical
actions. Despite his acquisition and use of numerous signs, Terrace decided that Nim
was incapable of combining words to create novel ideas. The only occasions in which
Nim produced combinations of signs were imitations of signs previously produced by his
trainers.
Central Washington
University's Chimpanzee
and Human Communication Institute
The CHCI at Central Washington University is
home to a family of 5 chimps who, according to their trainers, have mastered the use of
sign language and implement it in conversations with each other and their trainers.
The chimps at CHCI use the signs alone and in combination with other signs. One of
the longest recorded sentences produced by a chimp contained 7 signs! Chimps
generally utilize their signs in discussing aspects of family life. The trainers
have observed that young males frequently sign to talk about games, such as tickle and
chase.
An important finding about primate language use
at the CHCI is that the chimps use signs to refer to natural language categories.
For example, the chimps use one sign signifying "dog" to refer to all
dogs. This category generalization is similar to that of children as they first
begin learning to speak. Chimpanzees have also shown that they are able to create
novel signs by combining signs to convey a metaphorically different concept.
For example, one chimp at the CHCI was recorded describing a watermelon as "drink
fruit." Seems like a pretty accurate description!
The CHCI is considering a couple of possible
continuations of their research, provided that funding is available. One possible
area of exploration is the ability of chimps to use signs to represent spatial
relationships and their capacity for taking on the position of another person (or
chimp). Additionally, the CHCI is considering studying the ability of chimps to
recognize break-downs in conversations and to repair them, their use grammatical markers,
and their ability to understand and use temporal signs.
The CHCI also hopes to expand their research to
include the study of how to apply the teaching of language to chimps to assisting autistic
children, who have difficulty learning language. They also hope that their research
will be helpful in studying the teacher-student relationship in humans.
Click here to see more about what's going
on at the CHCI
The Orang Utan Language Project
At the National Zoo, Orang utans are learning
to communicate in a language designed especially for them. Their training began with
flash cards and has advanced to the use of computers with touch screens. Both nouns
and verbs are being taught with the goal of eventually testing the Orang utans ability to
develop syntactically accurate sentences. The Orang utan Language Project operates
under the idea that the orang utans will learn the language if they wish to use it to
communicate with their trainers and to control their environment. As such, no
coercion is used in teaching the language.
Click
here to learn more about what the orang utans are learning at the National Zoo and to try
learning a little symbolic language yourself.
Click here to read
a transcript of an on-line conversation with Koko the gorilla
-What does this
interview really suggest about primate language ability?
