COULD YOU EVER SPEAK CHIMPANZEE? 2. The Secret Code of Monkeys
Figure 1. A green monkey in Barbados, an island in the West Indies, calls out to send a message to other monkeys.
Figure 2. Vervet monkeys respond in different ways to alarm calls for their three main predators: leopards, eagles, and snakes.
Figure 3. Luna moth.
Figure 4. Green tree ants, also known as Australian weaver ants, join leaves together to make a nest.
Figure 5. Alex the parrot.
Animals communicate important messages that can mean the difference between life and death (see Figure 1). But do they know what they are communicating? And are the animals that receive the messages aware of what they mean?
Because we are aware of meaning in our speech and writing, it is natural for us to think that other creatures use language in the same way. Yet, in fact, much animal language is instinctive. The signaler often has no idea of the goal of its actions. The receiver, too, may react in a purely automatic, unthinking way.
Conversation between humans and a creature whose language relies entirely on instinct could never get very far. If such a creature responded at all to our signals, it would be in a dull, machinelike way. That would be the same as saying that a pianist has conversations with a piano, because when he or she presses a key, the instrument replies with a note!
But are there any animals that really understand what they are saying or hearing? Can any of them exchange signals about more than just their basic feelings?
Until quite recently, most experts would have answered "no" to these questions. They would have argued that no animals, except for humans, can express anything more than raw emotion – a cry of warning, for instance, or a scream of rage. Those experts would have claimed that no animal could invent or understand labels for things in the way that we do.
But now that view has changed. Studies have shown that some species do have a language in which labels and codes play an important part.
Clues Out of Africa
During the late 1960s, researcher Tom Struhsaker of the New York Zoological Society carried out a study of vervet monkeys in Kenya's Amboseli National Park (see Figures 2 and 3). He discovered that vervets have different alarm calls for their three main enemies: leopards, eagles, and snakes. Most interesting of all, he found that each type of call caused the vervets that heard it to behave in a very different way – a way that would help protect them from that particular predator.
When the vervets heard a "leopard" alarm call, they would scamper up the nearest trees. An "eagle" call caused the monkeys to look up at the sky and head for thick, low-lying bushes. Finally, a "snake" call made the animals stand up on their hind legs and peer into the long grass around them.
These findings by Struhsaker led to a lot of debate among scientists. Most experts at the time did not believe that the vervets actually understood what each of the alarm calls meant. According to this view, the monkey giving the alarm call simply cried out most excitedly if it saw a leopard, less strongly for an eagle, and least of all for a snake. Reacting to how excited the caller sounded, the other monkeys looked around and saw for themselves what kind of predator was coming. Then they responded to the danger in the most appropriate way.
A few scientists, though, had a different explanation. They claimed that the vervets' alarm calls stood for the ideas of leopard, eagle, and snake. In other words the vervets used a language in which certain ideas or objects were represented by certain sounds. That is exactly what humans do in languages all the time. But the notion that another species might also use labels for objects and ideas was quite bold and new.
In the years that followed, further studies confirmed that vervets really do use a labeling system. What is more, other kinds of monkey appear to understand language in the same way. Toque macaques in Sri Lanka, for instance, have special calls that an individual will use if it comes across an especially large supply of food or a favorite food plant. Other macaques become excited when they hear such a call, even when the food is out of sight. This behavior suggests that they understand exactly what the call means.
Following the pioneering efforts by Strusaker and others, more and more researchers began to observe how monkeys and their relatives communicate. Soon this was to lead to another remarkable discovery.
For years, scientists had assumed that all animals communicate only by instinct or by displays of basic emotion. Now, the scientists knew that some creatures could use simple "words" to describe objects that were familiar and important to them. If these animals could use language in this way, then they might be able to learn new words or labels from a human teacher.
Still, the ability of vervets and other monkeys to communicate appeared to be limited. Although they used a language based on words or labels, their vocabulary seemed to be quite small. They could signal to each other with a few different grunts and chatters. That was all they could say – or was it?
If you listen to people speaking quickly in a foreign language, much of what they say appears to be run together. It is hard to tell where one word ends and another begins, because you have no idea what the sounds mean. Your ear has not been trained to pick out the small, separate sounds of the language. Could it be that we make the same mistake when listening to the "speech" of animals?
To find out, Steven Green of the University of Florida made various recordings of the "coo" call of Japanese macaques (see Figure 4). Each recording was made in a different situation. He then passed these recordings through a special instrument that spread apart the sound and displayed exactly what it looked like on a chart. To the human ear, all coos of Japanese macaque sound the same. Green's results, though, showed just how easily we can be fooled. Each coo, when plotted out, followed a different pattern. It became clear that the macaques were using not just one call over and over again, but a wide variety of different calls, depending on the situation.
Certain grunts that vervet monkeys make when they meet each other also sound identical to our ears. But again, when examined closely, these grunts turn out to be quite different. As far as the vervets are concerned, they have completely different meanings. Studies of other monkeys have shown the same secret inner structure to their language.
Perhaps it is not surprising that monkey language should be similar in some ways to our own, even if it is much simpler. Physically, human and monkeys share many characteristics. But there is one group of animals to which we are even more closely related. That group, which includes the chimpanzee and gorilla, is the apes.
|The Conversational Parrot
For more than 20 years, Irene Pepperberg of Northwestern University in Evanston, Illinois, trained an Africa gray parrot named Alex (see Figure 5). He spoke the correct English words for 30 different objects, six colors, five shapes, and quantities from one to six. Unlike other talking birds, Alex used these words in the right way at the right time. He learned the word gray, for instance, by asking the color of his reflection in the mirror. He asked for objects that he wanted and would even ask for "tickling." Alex showed that real conversations are possible between humans and animals, and that he, at least, was no bird-brain!