A recent study finds that Eurasian jays can pass a version of the “Marshmallow test” and that the smarter jays had the greatest self-control. The original Marshmallow test tested children to see if they could resist eating one marshmallow if they were offered two later. So enterprising researchers decided to try it on smart birds:

To test the self-control of ten Eurasian jays, Garrulus glandarius, researchers 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 period of time.

Instead of marshmallows, the jays were presented with mealworms, bread and cheese. Mealworms are a common favourite; bread and cheese come second but individuals vary in their preference for one over the other.

The birds had to choose between bread or cheese — available immediately, and mealworm that they could see but could only get to after a delay, when a Perspex screen was raised. Could they delay immediate gratification and wait for their favourite food?

A range of delay times was tested, from five seconds to five and a half minutes, before the mealworm was made available if the bird had resisted the temptation to eat the bread or cheese.

All the birds in the experiment managed to wait for the worm, but some could wait much longer than others. Top of the class was ‘JayLo’, who ignored a piece of cheese and waited five and a half minutes for a mealworm. The worst performers, ‘Dolci’ and ‘Homer’, could only wait a maximum of 20 seconds…

The birds that performed better in these tasks also managed to wait longer for the mealworm reward. This suggests that self-control is linked with intelligence in jays.

University of Cambridge, “Just like humans, more intelligent jays have greater self-control” at ScienceDaily (October 22, 2022) The paper is open access.

The researchers offer some comments:

Jays are members of the corvid family, often nicknamed the ‘feathered apes’ because they rival non-human primates in their cognitive abilities. Corvids hide, or ‘cache’, their food to save it for later. In other words, they need to delay immediate gratification to plan for future meals. The researchers think this may have driven the evolution of self-control in these birds.

Self-control has been previously shown to be linked to intelligence in humans, chimpanzees and — in an earlier study by these researchers — in cuttlefish. The greater the intelligence, the greater the self-control.

The new results show that the link between intelligence and self-control exists across distantly related animal groups, suggesting it has evolved independently several times.

Of all the corvids, jays in particular are vulnerable to having their caches stolen by other birds. Self-control also enables them to wait for the right moment to hide their food without being seen or heard.

University of Cambridge, “Just like humans, more intelligent jays have greater self-control” at ScienceDaily (October 22, 2022)

Some questions arise at this point. Jays clearly have a well-developed sense of timing — required by their life circumstances — about when to eat and when to wait. It’s easy to see how self-control would vary with general intelligence because the test requires the bird to fix the sequence of the preferred reward in its memory. Thus an intelligence test compares one jay with another in this regard.

But what about the interspecies comparisons offered (humans, chimpanzees, and cuttlefish)?

We are only just beginning to explore the extraordinary intelligence of cephalopods like cuttlefish — with octopuses currently getting the most attention. But cuttlefish can pass up a snack too, researchers say, if they have reason to expect something better, which means that they can fix an expected sequence of events in memory. No surprise, chimpanzees show a similar ability.

But now, let’s look at crows. Crows are considered smart birds, according to tests. But the park crows in my neighborhood survive on scraps thrown by passing humans. Their intelligence is signaled by their ability to spot and follow frequent or probable donors from a distance and prepare for sudden swift descents. No waiting; the first crows to land just grab the biggest possible beakfuls and fly off — often closely pursued by less fortunate crows. Self-control has little to do with how the park crow generally feeds itself. As a marker for intelligence, we must limit self-control to situations where it makes a difference.

The “just like humans” claim in the media release prompts some careful thought

Many studies of humans have linked “sustained delay of gratification” with greater intelligence but some cautions are surely in order:

● Self-control is promoted in most cultures as an essential moral quality, quite apart from any specific reward. Lack of self-control is punished, often as a matter of principle. People who lack self-control are often shunned.

● The proposed reward for self-control — apart from avoidance of punishment — is often abstract or ethereal. “The satisfaction of doing the right thing,” “building character,” or “greater assurance of salvation” loom large in such schemes. Such rewards don’t appeal to all humans but one would need to be human to even consider them. Or to see that self-control is part of the foundation of all virtues and of the life of the mind.

● The relationship between human intelligence and self-control in life — as opposed to psychological testing — is complex. Intelligence may lead a child to see that controlling her impatience is critical to solving a math problem. But then, controlling her impatience well enough to get help with the math problem — and thus solve it — will make her more intelligent, for practical purposes. The boy genius who was raised to believe that self-control is for lesser beings might be able to solve the math problem himself — but unable to stick to anything long enough to make his gifts count, he achieves very little, compared to his potential.

It’s worth noting, in passing, that the Marshmallow test is no longer as highly esteemed as a predictor for humans as it once was: “As with so many studies, a lot depended on the children’s overall circumstances… self-monitoring and self-restraint take many years of practice so using the study as a predictor (which was not really intended by the authors) is not recommended.”

You may also wish to read: Can waiting for a marshmallow predict a child’s future? Believing so was all the rage in recent decades but later research didn’t back up the idea. It takes many years to develop self-restraint and whether it is even a smart move can depend on a child’s life circumstances, researchers found.