Many researchers wonder if chimpanzees are really able to use language in a rudimentary way, or if it is just created by operant conditioning. Psychologists realized, as far back as 60 years ago, that chimps would never be able to learn spoken language. They do not have the specialized tongue, lips, teeth, facial muscles, and palate that humans do to make the vast array of speech sounds that humans do. Researchers have instead tried to teach chimps some visual form of language.
An example is Beatrice and Allen Gardner’s experiment with American Sign Language (ASL). They started their research with a one-year-old chimp named Washoe, whom they raised like a child. The Gardners and their researchers signed to Washoe and one another just like deaf parents might do. Whenever Washoe signed correctly, she was rewarded. Because Washoe was raised amongst her caretakers, she had a lot of practice signing throughout her daily life. After four years of training, she had acquired about 160 signs. The Gardners saw many similarities between Washoe’s progress and that of a young child learning spoken language. Once she had learned a certain sign, she appropriately generalized its use to other objects or activities. For example, when she learned the sign for more to ask for more tickling, she used it to ask for more food or more play. Many of her mistakes seemed similar to ones children would make. After she had learned eight or so signs, she started using them in combinations, such as more sweet; later, she combined three or more signs to make statements or commands. By the age of five, the Gardners thought that her language resembled a three-year-old child’s.
In a different research project, psychologist David Premack taught a chimp, Sarah, language using small plastic symbols of different colors and shapes, which each stood for a word. Sarah learned to make simple sentences by arranging the symbols on a board. This system is easier for a chimp than ASL is. Because the symbols were right in front of her, she could use them as cues to remember the meanings. One disadvantage was that Sarah became mute when she didn’t have her symbols.
In another research project, Duane Rumbaugh taught a chimp named Lana to use a special typewriter linked to a computer. It had fifty keys, each showing a geometric configuration that represented a word. When Lana typed a configuration, it showed up on the screen in front of her. She learned to correct herself by checking the sequence of configurations as they appeared. Lana learned to respond to humans who talked through the computer and she initiated conversations. When Lana came across an object that she hadn’t been taught a word for yet, she sometimes made up her own.
Some researchers have argued that language-trained chimps use symbols and signs meaningfully and accurately. They are able to refer to things that have been removed, like ball they previously saw but that is now put away in a box. Also, like Lana, there is evidence that chimps can make up new appropriate word combinations using simple grammar rules. This suggests that chimps may have at least some understanding for elementary syntax.
Not all researchers agree with the above view. Psychologist Herbert Terrace spent almost four years teaching sign language to a male chimp named Nim. Terrace was convinced that this chimp was really combining words into grammatical groups similar to a child’s first sentences. But after analyzing his data, he began to doubt this. For example, a child’s sentences rapidly grow in length and complexity as the child learns more grammatical rules; Nim did not show the same progress. Even though he did produce some lengthy sequences, his mastery of syntax did not grow. Terrace analyzed videos showing conversations with Nim which showed that much of his talk was partial imitations of things the researcher had just said. This led Terrace to believe that prompting by trainers with a reward may be a reason for a chimp’s language usage. Terrace argued that while chimps may have the potential to create grammatical sentences, no one has proven it.
Another question is whether chimps really understand that words are symbols for something else. Their signs may be just operant behaviors used to get a desired treat; a chimp may learn the sign for banana to get a banana as a reward. The chimp may just see the signs not as a symbol, but as a behavior that results in a reward. If this is the case, then chimps are using words in a very different way than children do. Chimps rarely ask the names of new objects or actions, as curious children do. And they do not often call attention to things they are doing or seeing.
Researcher Savage-Rumbaugh attempted to teach naming to two chimps, Sherman and Austin. They were taught to use symbols on a keyboard to represent words for objects, actions, and qualities. In one test, the researchers put several different kinds of food on a table out of sight of the chimps’ keyboard. Each chimp was allowed to go over to the table and choose which food he wanted to eat and then go back to the keyboard and state his choice. Then the researchers had the next chimp retrieve the desired food. If the chimp came back with the right food item, he could eat it. If the chimp brought the wrong food, the researcher showed disappointment and pointed to the symbol the chimp had used. Both Austin and Sherman learned to do this and similar naming tasks with few mistakes. Their trainers thought that the chimps really did understand that the keyboard symbols stood for certain things.
Some researchers do not believe that Sherman’s and Austin’s behaviors prove that they have an understanding of words as symbols and they do not think that the chimps use the same cognitive processes as humans do.. The two chimp’s trainers say that they never meant to imply this and that we should not expect chimps and human children to be cognitively equal. Children have an innate ability to learn language easily and chimps do not; chimps can only do this after long, repetitive training. There are also definite limits to the types of things that a chimp can use language to communicate about.
Other animals do not have the capability to communicate the complicated thoughts that humans do. Even though other animals may have some ability to learn basic features of language, the complex and diverse use of language seems to belong strictly to humans.