Chimps know when they're guessing which cup is hiding food

Embargoed until: Publicly released: 2024-06-12 09:01

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Even without language, chimpanzees (Pan troglodytes) are capable of logical reasoning and know when their choices are lucky guesses rather than certainties, according to UK scientists who tested nine chimps at Edinburgh Zoo. The chimps were shown pairs of cups, one hiding a delicious snack, the other empty. Sometimes, the chimps were shown where the food was being hidden, but sometimes they weren't. After picking a cup, the chimps were offered the opportunity to pick between the remaining cup, with the risk that it was another dud, or a smaller, but certain, snack. They were more likely to opt for the safe, smaller snack if they hadn't seen the original cup and food setup. The researchers then upped the number of cups, but didn't allow the chimps to see which was hiding food, finding the same effect. Following a failure with their first choice, the chimps again went for the small but secure reward. Further experiments showed the animals were flexibly updating their responses based on the results of their first choice of cup, suggesting language isn't required to reason logically, the researchers say.

Media release

From: The Royal Society

Chimpanzees (Pan troglodytes) recognise that their guesses could be wrong and can pass a two-cup disjunctive syllogism task

Here we utilise a novel modification, post-decision wagering, to a simple 2-cup search task to show that chimpanzees are aware that their guesses aren’t certainties and could be wrong. Secondly, we use the same approach to show that, if we give the chimpanzees information about the contents of the cup which they didn’t choose, then they are able to infer the contents of their chosen cup, and adaptively choose between it and a fractional reward.

Guessing game – Chimpanzees understand that, when making some choices, they are relying on lucky guesses. Nine chimpanzees housed at Edinburgh Zoo were given a series of tasks where food rewards were hidden under cups. Chimpanzees were more likely to take a smaller, visible reward than take a risk choosing a cup potentially hiding food. Taken together, the experiments show that these logical reasoning abilities are present in non-human animals, and language is not an essential pre-requisite.

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Journal/
conference: Biology Letters

Research:Paper

Organisation/s: University of St Andrews, UK

Funder: This work was supported by the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013)/ERC grant agreement no. 609819, SOMICS and Templeton World Charity Foundation, grant ID: TWCF0314. Edinburgh Zoo’s Budongo Research Unit is core supported by the Royal Zoological Society of Scotland (registered charity number: SC004064) through funding 6 royalsocietypublishing.org/journal/rsbl Biol. Lett. 20: 20240051 generated by its visitors, members and supporters, and by the University of St Andrews (registered charity number: SC013532) who core supports the maintenance and management costs of the research facility.

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