Chimpanzee willpower is directly related to their smarts, so does self-control has an evolutionary role in intelligence?

Fifty-eight years ago, psychologist Walter Mischel first administered the marshmallow test. The premise is simple: children are taken into a room with a single marshmallow on a plate and told they can either eat it right away or double their marshmallow quota by resisting temptation for a tortuous 15 minutes.

As someone who finds the sickly puffy marshmallow deeply unpleasant, I’d probably end up eating it right away to avoid having to eat the second one, but clearly it presents some children with quite the dilemma, as the video below demonstrates.

According to the early studies, reactions were similar back in 1960 too. Children would “cover their eyes with their hands or turn around so that they can’t see the tray, others start kicking the desk, or tug on their pigtails, or stroke the marshmallow as if it were a tiny stuffed animal.” More impulse driven children would, on the other hand, simply devour the marshmallow as soon as their handler left the room.

So why would you put children through this torment? Mischel was looking to get a handle on when the idea of delayed gratification develops in humans. But the really interesting stuff came in the first follow up study in 1988 which demonstrated that children who could resist the lure of the marshmallow would go on to perform better in all kind of metrics from academic performance to BMI. “Preschool children who delayed gratification longer in the self-imposed delay paradigm, were described more than ten years later by their parents as adolescents who were significantly more competent,” apparently (though I’m sure the parents didn’t put it quite that callously.)

Not just humans

A new study from Georgia State University seems to echo these findings elsewhere in the animal kingdom: chimpanzees. Published today in Current Biology, the paper reveals that chimps who show self-control in a modified version of the marshmallow test also perform better in the Primate Cognitive Test Battery – a series of general intelligence measures which test things like the primate’s ability to follow a pointing finger, for example.

But how do you explain the nature of the challenge to a chimp? “That’s the great thing about our version of the marshmallow test – no training is required,” study author Professor Michael J. Beran tells me via email. “Chimpanzees see a large pile of food, and they see one item at a time being placed into containers within their reach. If they take that food, they forfeit the rest. It does not take them long at all to realise they have to wait if they want to get more. Sometimes, they learn this in the very first trial.”

Given the correlation with overall intelligence, the researchers believe that willpower must have some evolutionary merit to it. “I think self-control has a lot to do with natural behaviours in the wild, not just for chimpanzees but also other primates,” explains Beran, highlighting the ability to wait for fruit to ripen, or waiting to approach a potential mate until after a more dominant rival moves on. “I also think that any time a chimpanzee uses a tool to extract a rich food source, and especially if it must transport that tool, you see evidence of delayed reward (relative to, for example, eating something available more immediately, like vegetation). And, I think this also might reflect a more future-oriented perspective as well.” In other words, just like the human children who have better life prospects, good things come to chimps who wait.

And do the waiting chimps exhibit similar symptoms of frustration to the children? While that wasn’t measured in this particular test, Beran recalls a past piece of research where chimps were split test between those with no distractions and those with toys, crayons and magazines. When they had toys to distract them, they waited longer.

“This was interesting, but not the best part of the story,” Beran explains, adding that they had a third condition with the same toys and crayons, but a clear divider between them and the food, meaning they had no choice but to wait. “When we compared the time spent playing with toys, we found that they played with toys more often when they had to make themselves wait, versus when we made them wait,” he continued.

“We concluded this was a form of self-distraction very much like that which children employ in the marshmallow test to help themselves wait longer. So, chimpanzees seem to have some awareness of their own fallibility in these tests, and in at least some cases they can respond to that by distracting themselves from the rewards.”

So what are the next steps? Beran says that as well as looking to see if the results are replicated in other primate species, there’s also the question of genetics to ponder. “[Co-author] Dr Hopkins is an expert in these areas, and can look at genetic markers and various brain-behaviour relations such as examining the development and connectivity of certain brain areas in chimpanzees and their performances on tasks such as the one we used here,” he says.

But like the chimps patiently hanging on for their containers full of food, you’ll just have to wait to see how those studies pan out.