Plus Advent Calendar Door #8: Monkeys play the peanut lottery

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A capuchin monkey.

A capuchin monkey.

Maths is useful for everyone, not just humans. To be successful in your hunting and foraging, and to keep track of your family members and predators, you need to be able to gauge quantities, which is why numerical ability developed early on in evolution. Many animals, including some fish and insects, use some sort of understanding of quantities to navigate their lives.

That's a very basic type of maths, but what about something a little more sophisticated, such as, for example, probabilities? A 2017 study with capuchin monkeys addressed this question, and seems to suggest that, at least some of them, have an intuitive grasp of chances.

The study involved researchers appearing to randomly pick a treat from a jar which contained a mixture of tasty peanuts and not-as-tasty monkey pellets, in full view of a hungry monkey. The researcher would conceal the treat in one hand, and use the other hand to pick another treat from a different jar containing a different proportion of peanuts and pellets. Both hands were then offered to monkey, to see if it would go for the hand that had picked from the jar that contained a higher proportion of peanuts (see the video below). The fact that some of the monkeys tended to do so, the researchers suggested, shows that they have a grasp of probabilities. To find out more about the study read this article.

A monkey making its choice. (The monkeys that took part in the study did't have to live in these little cubicles, they only came into them for the chance of a treat.) Video from Springer, Animal Cognition, Intuitive Probabilistic Inference in Capuchin Monkeys, 2016, Tecwyn, E.C., Denison, S., Messer, E.J.E. et al., with permission of Springer.

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