Quoth the raven
Now, it seems, even the bird-brained have theories of mind
The Economist, 13 May 1004
like to regard themselves as exceptional. Other animals do not have
complex, syntactical languages. Nor do most of them appear to enjoy the
same level of consciousness that people do. And many philosophers
believe humans are the only species which understands that others have
their own personal thoughts. That understanding is known in the trade
as having a “theory of mind”, and it is considered the gateway to such
cherished human qualities as empathy and deception.
have learned to treat such assertions with caution. In particular, they
have found evidence of theories of mind in a range of mammals, from
gorillas to goats. But two recent studies suggest that even mammalian
studies may be looking at the question too narrowly. Birds, it seems,
can have theories of mind, too.
Proceedings of the Royal Society, Bernd Heinrich and Thomas Bugnyar of
the University of Vermont, in Burlington, describe a series of
experiments they have carried out on ravens. They wanted to see how
these birds, which are known to be (at least by avian standards) both
clever and sociable, would respond to human gaze.
gaze is reckoned to be a good measure of the development of theory of
mind in human children. By about 18 months of age most children are
able to follow the gaze of another person, and infer things about the
gazer from it. Failure to develop this trick is an early symptom of
autism, a syndrome whose main underlying feature is an inability to
understand that other people have minds, too.
To test whether
ravens could follow gaze, Dr Heinrich and Dr Bugnyar used six
six-month-old hand-reared ravens, and one four-year-old. The birds were
sat, one at a time, on a perch on one side of a room divided by a
barrier. An experimenter sat about a metre in front of the barrier. The
experimenter moved his head and eyes in a particular direction and
gazed for 30 seconds before looking away. Sometimes he gazed up,
sometimes to the part of the room where the bird sat, and sometimes to
the part of the room hidden behind the barrier. The experiment was
Dr Heinrich and Dr Bugnyar found that all the birds
were able to follow the gaze of the experimenters, even beyond the
barrier. In the latter case, the curious birds either jumped down from
the perch and walked around the barrier to have a look or leapt on top
of it and peered over. There was never anything there, but they were
determined to see for themselves.
A suggestive result, but not,
perhaps, a conclusive one. However, the second study, carried out by Dr
Bugnyar when he was working at the University of Austria, and published
last month in Animal Cognition, suggests that ravens may have mastered
the art of deception too.
In this case, the observation was
serendipitous. Dr Bugnyar was conducting an experiment designed to see
what ravens learn from each other while foraging. While doing so he
noticed strange interactions between two males, Hugin, a subordinate
bird, and Munin, a dominant one.
The task was to work out which
colour-coded film containers held some bits of cheese, then prise the
containers open and eat the contents. The subordinate male was far
better at this task than the dominant. However, he never managed to
gulp down more than a few pieces of the reward before the dominant
raven, Munin, was hustling him on his way. Clearly (and not
unexpectedly) ravens are able to learn about food sources from one
another. They are also able to bully each other to gain access to that
But then something unexpected happened. Hugin, the
subordinate, tried a new strategy. As soon as Munin bullied him, he
headed over to a set of empty containers, prised the lids off them
enthusiastically, and pretended to eat. Munin followed, whereupon Hugin
returned to the loaded containers and ate his fill.
At first Dr
Bugnyar could not believe what he was seeing. He was anxious about
sharing his observation, for fear that no one would believe him. But
Hugin, he is convinced, was clearly misleading Munin.
happened, Munin was no dummy either. He soon grew wise to the tactic,
and would not be led astray. He even stooped to trying to find the food
rewards on his own! This made Hugin furious. “He got very angry”, says
Dr Bugnyar, “and started throwing things around.” Perhaps ravens have
something else in common with people—a hatred of being found out.