Pigeons seem to have an innate ability to compute probabilities 鈥� the first non-primate shown to do so. The skill could help the birds forage for food and avoid predators, suggesting that there are good evolutionary reasons why pigeons might instinctively understand percentages.
Even as 12-month-old infants, between two toy jars if one contains a high ratio and one a low ratio of preferred to non-preferred toys. Non-human apes and even seem to have this instant and innate ability with probability too 鈥� prompting researchers to wonder whether other animals do.
and his colleagues at Western University in London, Ontario, Canada decided to find out using pigeons 鈥� birds with a surprising flair for numbers. They placed eight pigeons individually in a cage with access to two keys. Periodically one of the two keys lit up 鈥� by pecking it, the pigeon had a chance of receiving a food reward.
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Each key lit up a total of 24 times, but one key had a far greater probability of yielding a reward: it did so 18 times (75 per cent chance of reward), while the second key did so just six times (25 per cent chance).
Take your chances
Every so often both keys lit up at the same time and the pigeons had to choose which one to peck. As soon as the pigeons were familiar with the setup they showed a strong preference to pick the 鈥�75 per cent鈥� key when given this choice 鈥� they did so more than 85 per cent of the time.
But it was unclear whether the pigeons preferred the 鈥�75 per cent鈥� key because it had a greater probability of yielding a reward or simply because it gave out more rewards in total 鈥� 18 versus six.
In a follow-up test with eight different pigeons, Roberts鈥� team tweaked the setup. Now, one of the keys lit up 12 times and yielded a reward nine times 鈥� a 75 per cent chance 鈥� while the second lit up 36 times and also yielded a reward nine times 鈥� a 25 per cent chance.
Again, periodically both keys lit up at the same time. As in the first experiment, as soon as the pigeons were familiar with the setup they showed a strong preference for the 鈥�75 per cent鈥� key 鈥� pecking it about 90 per cent of the time. In other words, it really was the probability that mattered.
Roberts says the experiments suggest pigeons have an innate ability with probability 鈥� just like primates do.
at Whitman College in Walla Walla, Washington 鈥� 鈥� thinks the conclusion is reasonable, but he adds some caveats. 鈥淭hat was a relatively strong 75:25 difference,鈥� he says. If the probability difference was more subtle he thinks pigeons might have to learn over many trials which of the two keys to peck.
It makes evolutionary sense for pigeons to have an innate understanding of probability, says Roberts. 鈥淭here鈥檚 been lots of work on optimal foraging theory, suggesting animals will prefer habitats that contain a higher percentage of preferred food items and avoid habitats containing a higher proportion of predators,鈥� he says: pigeons may have been naturally selected to quickly detect and act on those probabilities.
