Jays with greater intelligence have more self-control

Self-control – the capacity to resist immediate temptation in favor of a better but delayed reward – is a crucial skill that underpins effective decision-making and future planning. This ability has been previously shown to be proportionally linked to intelligence in humans, chimpanzees, and cuttlefish. 

Now, a research team led by the University of Cambridge has discovered that Eurasian jays (Garrulus glandarius) – a member of the corvid family often nicknamed the “feathered apes” due to their high cognitive abilities – can pass a version of the “marshmallow test” (a test designed to study self-control in children), and those with the greatest self-control also score high on intelligence tests. These findings show that the link between self-control and intelligence appears across distantly related animal species, suggesting it has evolved independently several times.

Among all the corvids, jays in particular are vulnerable to having their catches stolen by other birds. Thus, the capacity for self-control may have evolved to enable them to wait for the right moment to hide their food without being seen or heard by potential thieves.

To test this ability in ten Eurasian jays, the scientists designed an experiment inspired by the 1972 Stanford Marshmallow Test, in which children were offered a choice between one marshmallow immediately, or two if they waited for a sufficient period of time. In this case, the jays were presented with mealworms (their favorite food), cheese, and bread. They had to choose between bread or cheese (available immediately) or mealworm that they could see but could only get access to after a period of delay ranging from five seconds to five and a half minutes.

All the jays managed to wait for the worm, but some seemed to have much more patience than others. For instance, one of them – called by the scientists JayLo – ignored a piece of cheese and waited five and a half minutes for a mealworm, while others could only wait a maximum of 20 seconds.

“It’s just mind-boggling that some jays can wait so long for their favorite 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,” reported study lead author Alex Schnell, a psychologist at Cambridge.

The scientists also presented the jays with five cognitive tasks which are commonly used to measure general intelligence. The birds that performed better in these tests also managed to wait longer for the mealworm reward, suggesting that self-control is linked to intelligence in jays too.

“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,” Schnell concluded.

The study is published in the journal Philosophical Transactions of the Royal Society B: Biological Science.  

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By Andrei Ionescu, Earth.com Staff Writer