Re: Chimps or chumps?

From: Stephen E. Jones (
Date: Thu Jan 27 2000 - 08:54:43 EST

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    Here is a short article from the Science & Technology pages of The Economist
    a month or so back. It reports on experiments with chimps which indicate that,
    unlike human children, chimps don't view humans (and therefore other chimps)
    as having minds.

    This suggests that chimps can be trained to emulate human behaviour which
    looks like it is based on human-like intelligence, but it is really just
    trial-and-error learning, like that which some other intelligent animals can do.




    Animal behaviour

    Chimps or chumps?

    ONE of the trademarks of being human is an understanding that others also
    have beliefs, intentions and desires. It has been called mindreading, or a
    "theory of mind", and it is what allows people to work together, to
    manipulate others, and even to deceive each other. The current belief is
    that the mindreading abilities of humanity's closest relatives, the great apes,
    are not fundamentally different from those of people; they are simply not as
    highly developed. But work just presented to a meeting of the Association
    for the Study of Animal Behaviour, at London Zoo, suggests this belief is

    According to Daniel Povinelli of the University of Southwestern Louisiana,
    the idea that an ape understands that another ape has any kind of mental
    life is an illusion. Their behaviour may seem to mimic that of people, but it
    is based on an entirely different understanding of the world-one that does
    not involve viewing others as psychological agents in their own right.

    Dr Povinelli and his colleagues looked at a very simple test of mindreading,
    the ability to understand seeing. When a person looks in a certain direction,
    children as young as three interpret that movement of the head or eyes in
    terms of the person's underlying psychological state-what the person is
    attending to, and what he intends to do next-and act accordingly. They
    are unlikely, for instance, to make a gesture towards someone who is not
    paying attention to them.

    To find out whether chimps did the same, Dr Povinelli's team confronted
    the animals with two experimenters. By extending an arm through a hole in
    a perspex cage towards one or other of the two, the chimp could expect a
    reward of an apple or a banana. But in a series of subtle variations, the
    experimenters' positions were altered so that only one of them could see
    the chimp. One experimenter was blindfolded while the other wore a
    blindfold over her mouth; one wore a bucket over her head while the other
    did not; one covered her eyes with her hands; one presented her back to the

    The results were startling. In three out of the four sorts of test, the chimps
    made their begging gestures just as frequently to the experimenter who
    could not see them as to the one who could. Occasionally, after receiving
    no reward from the "unseeing" one, they would gesture again, as if puzzled
    by the lack of response. Only in the case when an experimenter turned her
    back on the chimps did they stop gesturing to her.

    That raised the possibility that the chimps might be reasoning on the basis
    of some kind of postural cue-that a person's frontal aspect was a better
    predictor of reward than her back-rather than assessing line-of-sight. To
    test this, the two experimenters assumed identical positions, facing away
    from the chimp but twisting their bodies to look back at it over their
    shoulders. But only one of them actually turned her head to look at the
    chimp. The second continued to look away. Once again, the chimps failed
    the test, gesturing equally to both.

    These findings suggest that chimps are unable to equate seeing with
    knowledge in the way that human infants do. But that does not mean they
    are stupid. After enough practice, when the "correct" response was
    consistently rewarded, the chimps learned that front was better than back,
    face was better than back of the head, eyes open was better than eyes
    closed. Soon, they were reacting to the eyes just as a young child might.
    Their behaviour, however, was based on trial-and-error, not on an
    understanding of seeing. And when they were tested again a year later, they
    had forgotten this behaviour.

    Chimps seem to be able to hoodwink each other, and can follow the gaze
    of another chimp or human who has been distracted by something
    interesting. But according to Dr Povinelli, it is possible that in chimps,
    unlike in humans, those behaviours evolved separately from an ability to
    read another's thoughts. So it may be that our closest relatives do not share
    our empathy, but are instead "mindblind".


    ("Chimps or chumps?", The Economist, December 11th, 1999, p84)

    "Older folk in the know told me that selection didn't operate to make
    complicated things out of complicated things, only to make complex things
    out of simple ones. I couldn't understand how anything of the sort could be
    true, because, unlikely as it was, it would surely be less difficult to make a
    rabbit out of a potato than to make a rabbit out of sludge, which is what
    people said had happened, people with line after line of letters after their
    names who should have known what they were talking about, but
    obviously didn't." (Hoyle F., "Mathematics of Evolution", [1987], Acorn
    Enterprises: Memphis TN, 1999, p2)
    Stephen E. Jones | |

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