Animal behaviour

Thursday, July 1st, 2004

Many philosophers believe that humans are the only species with a “theory of mind”; they understand that others have their own thoughts. Animal behaviour looks at ravens, known to be both clever and sociable, and their theory of mind:

Response to 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 videotaped.

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.

I’m not surprised — but the next study gets more interesting:

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.

A quick aside: Hugin (Thought) and Mugin (Memory) are the names of Odin’s ravens in Norse mythology.

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 food.

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.

Doesn’t sound too different from elementary school.

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