Received: by alpheratz.cpm.aca.mmu.ac.uk id NAA20691 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-majordomo@mmu.ac.uk); Wed, 8 Nov 2000 13:53:28 GMT Subject: Fwd: Tests show a human side to chimps Date: Wed, 8 Nov 2000 08:49:53 -0500 x-sender: wsmith1@camail2.harvard.edu x-mailer: Claris Emailer 2.0v3, Claritas Est Veritas From: "Wade T.Smith" <wade_smith@harvard.edu> To: <skeptic@listproc.hcf.jhu.edu>, "memetics list" <memetics@mmu.ac.uk> Content-Type: text/plain; charset="iso-8859-1" Content-transfer-encoding: quoted-printable Message-ID: <20001108134958.AAA12833@camailp.harvard.edu@[128.103.125.215]> Sender: fmb-majordomo@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
Tests show a human side to chimps
By Gareth Cook, Globe Staff, 11/7/2000
http://www.boston.com/dailyglobe2/312/science/Tests_show_a_human_side_to_ch
imps+.shtml
Chimpanzees do many striking things that make them seem almost human in
their intelligence, such as building clever tools from sticks. But they
can also seem strangely dense, such as begging for food from someone who
has a bucket on their head and can't even see them.
Comparative psychologists have long held that only humans have what is
called a theory of mind, the ability to imagine the world from the point
of view of another. This conceptual sophistication - the reason we
understand a blindfolded man cannot see us, or why we might cry during a
movie - is one of the great boundaries between us and the other animals.
But now, in two new papers for the journal Animal Behavior, Harvard
graduate student Brian Hare and his colleagues describe a set of
experiments suggesting that chimpanzees, too, are able to consider life
walking with someone else's paws. The papers, one published in June and
another to be published soon, showed that, when something important such
as food is on the line, chimps are keenly aware of what their rivals are
thinking.
''This suggests that they are aware of what one another can or cannot
see,'' said Hare, whose research showed that a chimp is more likely to
charge in and grab a banana if he knows the local bully hasn't seen the
fruit, too. ''It is the strongest indication yet that chimpanzees have a
theory of mind.''
The last four decades of research into our closest living relatives has
been a narrative of falling boundaries. First, in the 1960s, researchers
found that humans are not the only ones to use tools. Then chimps were
found making tools, stripping the leaves off of a twig so it can be used
to fish for termites. By the 1980s, researchers had come to accept that
chimpanzees can learn abstract symbols and combine them to form sentences.
At every step, the results were greeted with enormous public enthusiasm
inspiring, for example, ''The Planet of the Apes'' movies, and encouraged
researchers to view other primates in ever-more human terms.
Now, though, researchers say that the quest to forge a bond with them
has, ironically, obscured our ability to see their true abilities. In the
Animal Behavior papers, for example, the breakthrough came not from
observing how chimpanzees can be trained to interact with humans, but
from observing, in a carefully controlled way, how they compete for food,
a behavior that is much closer to the wild.
''This is the revolution that's happening in the field,'' said Marc
Hauser, a Harvard professor who does cognitive research with monkeys.
''Many of our laboratory experiments now depend on observations from the
field. We are more sensitive to the ecological and social conditions the
animals live in.''
Sally Boysen, a professor of psychology at Ohio State University, has
used a similar approach to test her chimps' reactions to a predatory
event:
A chimp named Darrell was allowed to see a lab worker hiding behind a
barrier with a tranquilizer gun. Another chimp, named Kermit, was then
brought to the entrance of the cage.
In one case, where Darrell knew that Kermit could see the worker with the
gun, he was quiet. But if Kermit could not see the worker, Darrell
exhibited ''the whole range of stress responses'' to warn Kermit,
including a ''fear grimace,'' a ''bipedal swagger,'' and ''high-pitched
distress screams.''
''Kermit turned right around and left,'' said Boysen, whose results have
not been published. ''He never even entered the cage.''
But researchers have also found that chimpanzees can be surprisingly
unsophisticated about the perspective of another. Daniel Povinelli, a
professor of cognitive science at the University of Louisiana, said that
he found chimpanzees would beg for food from researchers even when they
had a bucket over their head.
The chimps, he explained, often play with the buckets and even put them
over their heads, so one would expect them to understand that the
researcher would be blind to their begging. The fact that they don't,
Povinelli argued, demonstrates the limits of chimp intelligence.
But the Animal Behavior experiments, Harvard's Hare said, took advantage
of the chimps natural competitiveness. All of them were conducted with a
dominant chimp at one end of a line of cages, and a subordinate one at
the other end. In each case, they wanted to see if subordinates would
change their behavior based on what the dominant one knew.
In the first experiment, researchers placed two bananas in the center,
with a small barrier that blocked one piece of fruit from the view of the
dominant one.
With a small head start, the subordinate chimp tended to go after the
obscured one, even though both bananas looked the same from where he sat.
In the second experiment, both were allowed to see a banana as it was
hidden. The experimenters then found that the subordinate one was more
likely to grab the food if they replaced the dominant chimp with one who
did not know the location of the food.
The two experiments were done by Hare and Josep Call and Michael
Tomasello of the Max Planck Institute for Evolutionary Anthropology in
Leipzig, Germany. Bryan Agnetta, of the Yerkes Regional Primate Research
Center at Emory University, was also a co-author of the first paper.
In humans, the ability to understand that someone else thinks, and may
think the wrong things, is an essential cognitive building block that
forms before preschool age.
It allows humans to make the kinds of subtle and complex social
calculations that order our daily life, and even fuel soap operas: Will
he believe my explanation if he finds out that I didn't invite him to the
party of my friend who doesn't like him?
In looking for the origins of this ability, researchers have turned to
chimpanzees, with whom we are thought to have shared a common ancestor
between 4 and 6 million years ago.
But it's an effort that must move with care, said Povinelli, who has
published a new book, called ''Folk Physics for Apes,'' which argues that
researchers have been too quick to ascribe cognitive sophistication to
chimpanzees, when there are simpler explanations for the behaviors.
''It's part of what makes these experiments difficult,'' Povinelli said.
''It's part of the nature of the human mind to transform things into
mental beings. We re-create them in our own image.''
This story ran on page F01 of the Boston Globe on 11/7/2000. © Copyright
2000 Globe Newspaper Company.
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