One crumb or two? Pigeons can work out their chances of getting the most food Findlay / Alamy Stock Photo

Pigeons seem to have an innate ability to compute probabilities – 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, humans instantly recognise the difference 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 some monkeys seem to …