Prattle of the Apes : Primates May Have More Facility for Language Than Once Thought

The young vervet monkey playing near the edge of the plain suddenly emits a sharp cry indicating the presence of a flying predator. Nearby adults look up briefly, see that it is only a pigeon, and return to their feeding. The performance is repeated frequently with hawks, other birds, and even falling sticks or branches.

Six months later, the young monkey has developed some discrimination and uses the alarm call only when he actually spots a bird. By the time he is 3 or 4 years old, the monkey has become very discerning and emits the alarm only when he spies an eagle, which preys on vervet monkeys.

“This type of learning behavior in response to environmental cues was previously thought to be unique to humans,” UCLA anthropologist Robert Seyfarth said. The grunts, squeaks and squeals characteristic of animal “language” were thought--and in some cases proved--to be instinctive.

This newly observed ability of monkeys in the wild to learn correct usage of “words” indicates that primates may be much closer to humans in their ability to use language than many scientists had thought. Seyfarth and his wife, Dorothy Cheney, also of UCLA, report their conclusion in a paper to be submitted to the journal Animal Behavior.

The question of whether primates are able to use language in a manner analogous to humans has bedeviled scientists since a chimpanzee named Washoe was first taught American sign language for the deaf in the 1960s. Primatologists conducting the experiments have argued that chimps can use language to express desires and needs and that they possess a rudimentary “grammar” that enables them to combine words to form new meanings.

Origin of Language

Critics have argued, in contrast, that the animals have merely learned to carry out certain repetitious motions to obtain a desired reward or that the animals take cues from the unconscious body language or facial expressions of their trainers.

The study of how these non-human primates learn language is important to the scientists because it gives clues both to how language originally developed in humans and to how it can more readily be taught to individuals born deaf.

Several recent developments lend strong support to the theory that primates actually use language like humans. One development is Seyfarth and Cheney’s observation that monkeys learn discrimination in the use of particular sounds. Another is the unexpected facility with which a pygmy chimp named Kanzi has learned language skills.

Perhaps even more unexpected was the observation that Washoe has taught sign language to another chimp without any prodding from instructors. And finally, a Japanese primatologist claims that he has taught an ape the abstract concept of counting.

“The earliest attempts to teach human language to non-human primates (in the 1950s) aimed--quite literally--to teach spoken English to chimpanzees,” Seyfarth writes in a forthcoming book called “Primate Societies.”

Although many investigators think that chimps can understand spoken English, “these efforts were failures, largely because the vocal apparatus of the chimpanzee prevents it from articulating many of the sounds used in human speech.”

One group of scientists, Seyfarth among them, then began to study the natural vocalizations of primates and found that they apparently have a surprisingly large “vocabulary.” Tom Struhsaker of the New York Zoological Society, for example, found that vervet monkeys have at least three different alarm calls--one for leopards, one for eagles and one for snakes.

In the early 1980s, Struhsaker, Seyfarth and Cheney recorded these calls in Africa and played them back to captive monkeys. Each call elicited an appropriate response. “The leopard alarm caused the monkeys to run up a tree,” Seyfarth said. “The eagle call caused them to search the sky. The snake call led them to stand on their hind legs and look down.”

It was the monkeys’ ability to develop discrimination in using these calls that led Seyfarth and Cheney to conclude in their new paper that the monkeys learn language the same way humans do.

The primates also have a repertoire of vocalizations for other situations and a surprising ability to recognize both the “speaker” and the meaning. Juvenile vervets, for example, frequently get into fights with other juveniles. These fights are characterized more by loud noises than by violence; the screams seem to be a call to their mothers for assistance.

Social Standing

Sally Gouzoules and her colleagues at the Yerkes Primate Center at Emory University in Atlanta have found that the scream reflects the social standing of the juvenile’s opponent. “The young monkey emits one scream when faced by a juvenile that is higher in the group’s pecking order,” Gouzoules said, “a second when the opponent is of equal rank, and a third when the opponent is lower in rank.”

The response of the mother might then vary as a result of the call. In the first case, she might rescue her child, and in the last case she might chase off the opponent. This type of study has been very useful, Seyfarth said, “not only because of the insight it provides into language, but also because it confirms that the dominance ranks within a primate group are real and not simply an artificial construct imposed on primates by scientists attempting to explain their behavior.”

Other scientists have chosen to study the communicative abilities of primates by teaching them an artificial language. Kanzi, a pygmy chimpanzee at the Yerkes center, is a prize specimen for these investigators because he has displayed unusual facility in mastering the use of lexigrams, which are plastic disks of different shapes and colors that represent individual words. “Kanzi can also understand spoken English,” said his trainer, E. Sue Savage-Rumbaugh of the Yerkes center.

Savage-Rumbaugh and her husband, Duane Rumbaugh, chairman of the psychology department at nearby Georgia State University, have taught language skills to other chimpanzees, particularly two specimens named Sherman and Austin. They were trying to teach the use of lexigrams to a pygmy chimp, Kanzi’s mother, when they observed that the 2-year-old Kanzi spontaneously began using several of the symbols correctly. “He had apparently learned their meanings simply by observing our efforts with his mother,” Rumbaugh said in a telephone interview.

They then shifted the training to Kanzi and found that he progressed much more rapidly than had Sherman and Austin, particularly in his mastery of such difficult skills as associating a word with an object. “It is relatively easy, for example, to teach a primate to select the symbol for, say, an apple when he wants an apple,” Rumbaugh pointed out. “It is much more difficult for the chimp to learn to pick an apple out of a group when the investigator selects the apple symbol.”

Most primates have to be taught various language sub-skills before they can make this connection between word and object. Kanzi, however, learned to make the association without any extra training. Savage-Rumbaugh speculated that this ease of learning arises from the pygmy chimpanzee’s increased intellectual capacity in comparison to gorillas, orangutans and common chimpanzees, the other three species of great apes.

Many primates also seem to understand spoken English, but critics argue that they are really interpreting facial clues and body language inadvertently provided by the speaker. Savage-Rumbaugh designed a special experiment to test this possibility. In the experiment, the trainer places a blanket over his head and body so that he cannot see the animal’s movements and thus influence the animal’s selections.

When asked by means of a computer keyboard to pick out one of three shuffled pictures of familiar objects, Sherman and Austin were correct nearly all of the time. When asked orally by the covered trainer, however, they were correct only slightly more often than would have been predicted by chance. Kanzi, however, correctly selected the correct picture nearly all of the time, even in response to oral commands.

Kanzi can also respond to relatively complex spoken sentences. When asked, for example, “Will you go get a diaper for your sister Mulika?” the chimp takes a diaper to his sister. Savage-Rumbaugh concludes that the chimp’s abilities are “about equal to those of a 1- or 2-year-old child”--despite the fact that Kanzi has to communicate through symbols.

Kanzi’s ability to pick up language unaided by humans is not unprecedented. Roger Fouts of Central Washington University in Ellensburg has found that chimps can teach sign languages to each other. Fouts has worked with a young chimp called Loulis.

At the age of 10 months, Loulis was placed in the care of Washoe, who had been taught hundreds of sign language words by R. Allen Gardner and Beatrice Gardner of the University of Nevada. “Washoe adopted Loulis and, within eight days, spontaneously began teaching him simple signs,” Fouts said in a telephone interview. “Washoe would demonstrate the signs for Loulis and occasionally we saw her take the young chimp’s hands and mold them into the proper sign, much as the Gardners had done with him.”

Today, at the age of 5, Loulis knows approximately 55 different signs taught him by Washoe and combines them in groups of two or three words to form sentences, Fouts reported in June at the American Assn. for the Advancement of Science meeting in Los Angeles. Loulis initially conversed primarily with Washoe, but now talks more often with a young male named Dar that is about his own age. Dar is one of three chimps raised like deaf children elsewhere and then moved into the compound with Washoe and Loulis. Loulis has also learned new signs from these three.

Japanese Experiment

A potentially more controversial result has been reported recently in the journal Nature by Tetsuro Matsuzawa of Kyoto University in Japan. Matsuzawa said that he has taught a 5-year-old chimp named Ai to identify 14 objects and 11 colors and, most surprising, to count up to six. Many primatologists have argued that counting represents too abstract a concept to be taught to animals.

If Ai is shown four green apples, for example, she presses three separate keys on a computer keyboard--one for each category of information. Her typical order would be “apples, four, green.” Matsuzawa reported that Ai achieved her proficiency with only 68 hours of training, and is correct about 98% of the time. Other investigators, however, would like to see the attempt repeated with other chimps before any conclusions are drawn.

Together, these results indicate that primates in general, and the great apes in particular, have a previously unsuspected ability to communicate with each other and with humans. Primatologists are now attempting to discover what other abilities they may possess.

But a particular problem, UCLA’s Seyfarth said, is distinguishing between lack of ability and lack of motivation. A chimp’s failure to accomplish a task may, just as with a balky child, represent only an unwillingness to perform under artificial conditions.