Worlds of David Darling > Children's
Encyclopedia of Science > Could You Ever Speak Chimpanzee? > 2. The
Secret Code of Monkeys
COULD YOU EVER SPEAK CHIMPANZEE?
a book in the Could You Ever? series by David Darling
2. The Secret Code of Monkeys
Animals communicate important messages that can mean the difference between
life and death. But do they know what they are communicating? And are the
animals that receive the messages aware of what they mean?
|A green monkey in Barbados, an island in
the West Indies, calls out to send a message to other monkeys
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
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. 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.
|Vervet monkeys respond in different ways
to alarm calls for their three main predators: leopards, eagles, and
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.
|A vervet monkey with baby
in Kenya, East Africa
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.
|Green tree ants, also known as Australian
weaver ants, join leaves together to make a nest
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. 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. 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