Although nonhuman animals have little or no ability to produce anything resembling human speech, they may have surprising ability to understand it. One of the more remarkable instances comes, not from an ape, but from a border collie. His name is Rico, and he is able to respond accurately to spoken requests to fetch different objects from another room, and then to either place the designated object in a box or bring it to a particular person. In experimental trials, he was given 10 objects randomly selected from 200 objects that he knows, and chose correctly in 37 out of 40 trials. Rico collects the designated object from a room in which there is no person who might cue him about the correct selection, which rules out any “Clever Hans” effect. If he is given an unfamiliar name of an object to fetch, he will choose the one object among the otherwise familiar selection that is novel. Four weeks later, he demonstrates that he still knows the name of this object, indicating what has been termed “learning by exclusion.” This ability to apply a label on a single trial is known as “fast mapping,” and has hitherto been thought to be restricted to humans. Rico’s exploits may not come as a surprise to people convinced that their pet dogs or cats can understand them.
Rico’s performance is somewhat comparable to that of Kanzi, a bonobo raised by Sue Savage-Rumbaugh. Kanzi is unable to speak, but as we shall see he has acquired an impressive facility to communicate by using manual gestures. What is interesting here is that his ability to understand spoken language far exceeds his ability to produce it. He can respond correctly to quite long sentences. For example, when asked, “Would you put some grapes in the swimming pool?” he immediately got out of the water, fetched some grapes, and tossed them into the pool. When visiting his friend Austin, a chimpanzee, he was told, “You can have some cereal if you give Austin your monster mask to play with.” He responded by finding his mask and giving it to Austin, and then pointing to Austin’s cereal. His ability to respond to such commands is not perfect, though. In one controlled study, he was given a list of 660 unusual spoken commands, some of them eight words long, and responded correctly on 72 percent of them. Kanzi was nine at the time, and did a little better than a two-and-a-half-year-old girl called Alia, who managed to get 66 percent correct.
These examples suggest that comprehension of speech far outstrips production, also a common observation in children acquiring language. They also suggest a surprising ability to break sentences down into words, hitherto considered a uniquely human capacity. Although this is something that seems natural to most of us, there is virtually nothing in the acoustic signal that tells us where one word ends and another begins, and it is really only experience with the language that enables us to break a sentence down in this way. Doyoufollowme? We become aware of this only when listening to a language that is completely foreign, when all the words seem to run together in a meaningless babble. When we teach children to speak, we help them to separate the words with an exaggerated form of speech known as “motherese.” The surprise, then, is not just that Rico and Kanzi were able to respond correctly to words, it is that they were able to pick them out at all. One must also suppose that they are not unique among their species—presumably, other apes and mammals are capable of the same thing, given the right conditions of learning. Keep talking to your cat.
It is unlikely, though, that the understanding exhibited by Rico and Kanzi—one hopes they might one day meet—meets the definition of true language comprehension. The identification of key words may be sufficient to provide the correct response most of the time. All Rico needs to know is the name of the object and the name of the recipient (box or person), and the rest follows. Although the sentence “You can have some cereal if you give Austin your monster mask to play with” involves recursion (specifically end-recursion), Kanzi probably did not need to parse the sentence in order to understand what he needed to do. He just needed to pick out the words cereal, Austin, and mask to have a pretty good idea of what was required.
~~ The Recursive Mind : The Origins of Human Language, Thought, and Civilization -by- Michael C. Corballis
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