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Remarkable self-control of jays is linked to their intelligence, University of Cambridge researchers show

Jays were able to demonstrate remarkable self-control in a version of the ‘marshmallow test’ conducted by University of Cambridge researchers.

The study provides the first evidence of a link between self-control and intelligence in birds, something previously demonstrated in humans, chimpanzees and - in earlier research by the same team - cuttlefish.

The ability to resist temptation in favour of a better, but delayed, reward can be seen as an important skill underpinning effective decision-making and future planning.

A Eurasian jay
A Eurasian jay

In a 1972 experiment called the Stanford Marshmallow test, children were offered a choice between one marshmallow immediately, or two if they waited for a period of time. Children were found to vary greatly in self-control and the ability has been linked to general intelligence. Those who can resist temptation for longer typically score more highly in academic tasks.

Cambridge researchers substituted marshmallows for mealworms, bread and cheese for their version of the test with 10 Eurasian jays (Garrulus glandarius).

Jays are members of the Corvid family, which can rival non-human primates in their cognitive abilities, and hide or ‘cache’ their food to save it for later. By delaying immediate gratification, they provide themselves with future meals - a technique that researchers believe may have driven the evolution of self-control in these birds.

For jays, which are particularly vulnerable to having their caches stolen by other birds, self-control is also valuable in helping them wait for the right moment to hide their food without being spotted.

In the study, the jays were able to choose between bread or cheese that was immediately available, or a preferred food - mealworms - which they could see, but only reach after a delay when a Perspex screen was raised. A range of delay times, from five seconds to five and a half minutes was tested before the mealworm was made available.

All the birds managed to wait for the worm, with some able to wait much longer than others.

One bird, nicknamed JayLo, waited an astonishing five and a half minutes. The worst performers, ‘Dolci’ and ‘Homer’, could only resist the available food for up to 20 seconds.

Dr Alex Schnell at the University of Cambridge’s Department of Psychology, first author of the report, said: “It’s just mind-boggling that some jays can wait so long for their favourite food. In multiple trials, I sat there watching JayLo ignore a piece of cheese for over five minutes – I was getting bored, but she was just patiently waiting for the worm.”

The jays looked away from the bread or cheese, as if distracting themselves from temptation - behaviour also seen in chimpanzees and children.

The researchers also found that birds that performed better in five cognitive tasks commonly used to measure general intelligence were able to wait longer for the mealworm, suggesting a link between self-control and intelligence in jays.

“The birds’ performance varied across individuals – some did really well in all the tasks and others were mediocre. What was most interesting was that if a bird was good at one of the tasks, it was good at all of them – which suggests that a general intelligence factor underlies their performance,” said Dr Schnell.

In another test where the worm was visible but always out of reach, the jays always ate the bread and cheese on offer. Their preference for these two foods varies, but they did not wait as long if the immediately available food was their second most preferred, compared to their third, demonstrating that they only delay gratification if it is worthwhile.

The results were published in the journal Philosophical Transactions of the Royal Society B.

The research was approved by the University of Cambridge Animal Ethics Review Committee and performed in accordance with the Home Office Regulations and the ASAB Guidelines for the Treatment of Animals in Behavioural Research and Teaching. It was funded by the Royal Society, Fyssen Foundation and European Research Council.

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