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Scientists think that animals think:
But what exactly do they think about?
By William J. Cromie
Do animals think?
"Of course they do," answers Marc Hauser, a Harvard professor of
psychology. "How could they not think and manage to survive in
Hauser has been studying animal cognition since 1980, when a
female spider monkey reached through the bars of her cage at
Florida's Monkey Jungle and gave him a hug. He was 19 years old
at the time. "She looked into my eyes and cooed several times,"
he remembers. "The experience got me to thinking about what
animals are thinking and how to find out."
He now believes that animals conceive the world in ways similar
to humans, especially species like chimpanzees who live a rich
social life. His field and laboratory experiments suggest that
humans got their mechanisms for perception from animals. "Those
mechanisms came free, courtesy of evolution," he says.
Hauser and his colleagues are trying to determine what sorts of
thinking processes are unique to humans and what processes we
share with animals. The one that comes immediately to mind is
"Animals have interesting thoughts, but the only way they can
convey them is by grunts, shrieks, and other vocalizations, and
by gestures," Hauser points out. "When humans evolved speech,
they liberated the kinds of thoughts nonhumans have. Feedback
between language and thinking then boosted human self-awareness
and other cognitive functions."
Monkeys get the rhythms
Clever experiments with monkeys and human infants show that they
share thinking processes once thought to be in the minds of
humans alone. Babies only 3-4 days old can tell the difference
between two languages such as Dutch and Japanese. When the
infants hear someone saying sentences in Dutch, they express
their interest by sucking rapidly on the nipples of pacifiers.
After a while they get bored with the Dutch talk and stop
sucking enthusiastically. If someone then starts speaking
Japanese, they will show increased interest by upping their
The babies don't know what the speakers are talking about, of
course, but they can discriminate between languages by the
change in rhythms. They don't respond to languages with similar
rhythms, such as Dutch and English or French and Spanish. Also,
if you play the same sentences backward, the infants fail to
react. "One explanation for this behavior is that they
intuitively know that no human vocal tract can produce such
sounds," Hauser explains.
If this is true, monkeys should not be able to make the same
distinctions because they don't know what rhythms and sounds
human vocal tracts can produce. But cotton-top tamarin monkeys
easily distinguish between Dutch and Japanese. They look at a
speaker broadcasting sentences of Dutch, look away when they're
bored, then look back when someone starts speaking Japanese. And
they cannot make that distinction when the sentences are spoken
"The monkeys have the same perceptual abilities as us," Hauser
concludes. "That means such perception did not evolve with human
speech; it existed before humans and speech evolved."
Babies do statistics
One big mystery about human cognition is how babies decide when
one word ends and another begins when they listen to an adult's
stream of speech. Experiments done in 1996 revealed that kids as
young as 8 months are capable of performing a kind of
statistical analysis that seems pretty amazing.
The babies listen to a continuous stream of consonants and
vowels, such as "dapikutilado...." Some combinations always
cluster together, like "da-pi-ku," while others do not. If
infants are aware of statistically familiar clusters, they show
little interest when they hear them. But when they hear
something like "da-ku-pi," they know something is unfamiliar.
They look toward the sounds of unfamiliar triplets longer than
they look in the direction of those that are relatively familiar.
The youngsters don't know it, but that's how they will get the
hang of separating words in a stream of speech. Linguists call
this "computing transitional probabilities." It sounds too
complicated for an 8-month-old, much less for a monkey. However,
Hauser and his two collaborators, Elissa Newport and Richard
Aslin, showed that cotton-top tamarins can do the same thing.
Perceptual and at least some computation mechanisms, therefore,
lived in the brains of animals long before humans came along,
even ancient humans who didn't do much more than grunt and
bellow. "Some people wouldn't call these abilities 'thinking,'"
Hauser admits. "That's fine with me. But it begs the question,
'What do you mean by thinking?'"
How high can animals count
Additional tests by Hauser and other researchers reveal that
monkeys can count up to four. The human ability to count to
higher numbers apparently came only after we evolved language
and developed words to describe quantities like 25 and 1,000.
Some human cultures still don't use large numbers. The Hadza
people, hunter-gatherers in Tanzania, for example, have words
only for "one," "two," and "three"; anything more is "many."
They are aware that a picture with 30 dots displays a larger
number than one with 20 dots (as are monkeys), but they have no
words for the precise numbers of dots.
The bottleneck between human and nonhuman thinking involves not
just words, but the ability to recombine words in an endless
variety of new meanings. That appears to be a unique human
capability. Chimpanzees have a rich social and conceptual life,
Hauser maintains, but they can't discuss it with each other.
The next step in determining how much thinking ability humans
share with other animals will involve scanning the brains of
both while they do the same cognitive tasks. Harvard
psychologists have already begun to do this in a collaboration
with researchers from the University of Massachusetts Medical
School in Worcester and the Max Planck Institute in Germany.
Monkeys may exhibit the same kind of intellectual behavior as
humans, but do they both use the same areas of the brain?
"We have a great deal of data that show what areas of the brain
are activated when humans respond to various situations," Hauser
points out. "Now we will determine if monkeys and other animals
utilize the same brain circuits."
So far, the monkeys are adapting well to experiments at the
University of Massachusetts. They move into harnesses in brain
scanning instruments, such as MRI machines, without difficulty.
Measurements of their stress levels show that after five days of
training, marmoset monkeys feel as comfortable as they do in
their home cages with their own social group.
For some people, such research will not provide a satisfactory
answer to the question: Do animals really think? These people
define thinking as having a sense of self, beliefs that go
beyond raw perceptions, emotions such as empathy, and the
ability to imagine a situation remote in time and place and
predict an outcome.
"Those capabilities cannot be illuminated by brain scanning,"
Hauser admits. "But experiments using other techniques are
beginning to shed light on what kinds of perceptual and
computation skills animals bring to analyzing the world, and in
what ways these skills are different from our own."
I think, therefore I am. - Descartes
For more information about nonhuman thinking, see Hauser's book
"Wild Minds," (Henry Holt, 2000). Hauser will debate
distinguished linguist Noam Chomsky on March 30 at Harvard at a
conference sponsored by the Language Evolution Society.
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