A recent study investigating cognitive flexibility concludes that in some situations, capuchin and rhesus monkeys are more adaptable than humans.

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A recent study pitted capuchin monkeys (pictured) and rhesus monkeys against humans.

Humans live in a complex world. As we learn to navigate it, we build up a series of rules in our brains.

Once we have discovered a way to do something, we are likely to continue doing it in the same way.

This is because finding new solutions can be cognitively demanding.

If something works well, it is usually easiest to stick with it — especially when there are plenty of other puzzles for us to solve in our daily lives.

However, for both monkeys and humans, the environment changes. As a result, sticking to learned rules is not always the most efficient tactic to adopt.

Stuck in a rut?

Many studies have shown that humans are particularly susceptible to becoming stuck in a learned rut.

For instance, in a classic study from the 1940s, researchers asked participants to solve a maze. The only way to complete it was by taking a circuitous zigzag route. However, halfway through multiple trials, the researchers altered the maze so that there was a much simpler shortcut.

The majority of the participants continued using the more complex and time consuming method. In other words, they stuck to what they knew, even when it was not the most efficient solution.

Recently, researchers from Georgia State University in Atlanta set out to discover if capuchin and rhesus monkeys could outperform humans when it came to this type of cognitive flexibility. They have published their findings in the journal Scientific Reports.

As the study authors explain, it is still not clear why humans often do not "look for better solutions once [they] have found an adequate one."


Lead study author Julia Watzek, a graduate student

In the latest study, the researchers worked with 56 human participants, 7 rhesus macaques, and 22 capuchin monkeys.

Both the humans and monkeys learned, through trial and error, to select three icons in a row to receive a reward. The humans won points or heard a jingle, whereas the monkeys received a banana pellet.

If the participants made the wrong choice, they heard a buzzer and received a 2-second time-out.

After 96 trials, the scientists changed the game. For the next 96 trials, to receive the reward, the participants only needed to hit the final icon without having to remember the position of the original two symbols.

In the trials this shortcut was available, all of the monkeys quickly adapted and began using the easier route. In fact, 70% began using it as soon as it became available. However, the humans fared less well, with 61% not using the shortcut at all.

Why did monkeys outperform humans?

The authors of the new study believe that monkeys appear to show more cognitive flexibility due to the amount of available working memory they have.

Working memory refers to our ability to hold multiple things in our minds at once for a short amount of time. Monkeys, in general, have less working memory than humans.

Some earlier work backs this theory up. In one study, for instance, researchers asked participants to complete complicated math problems.

They found that those with access to more working memory tended to stick with a complicated learned rule. However, those with less working memory tended to search for and adopt simpler alternatives when they were available.

This, the authors believe, might be because those with less available working memory found the complex rule to be a cognitive strain and wanted to find simpler alternatives.

At the same time, those who had more working memory would not feel the cognitive strain so acutely, meaning that they were less incentivized to look for an alternative solution.

In the new study, the participants needed to hold the position of the initial symbols in their working memory. In the later trials, the shortcut allowed them to reduce the strain on their working memory.

Because working memory is more constrained in monkeys, they were likely more eagerly hunting for a new and simpler solution. However, because the task did not pose too much difficulty for humans with their greater access to working memory, they were less motivated to look for other solutions.

A small piece of the puzzle

Although these results are intriguing, the study only used one method of measuring cognitive flexibility. Of course, cognitive flexibility depends on a wide range of factors, including the environment, the type of challenge, and how motivated one is to be flexible.

For instance, a monkey's primitive drive to obtain food might outweigh a human's desire to win points or hear a jingle. Perhaps this difference in the level of motivation made the monkeys more likely to experiment and investigate potential shortcuts.

With that said, the theory that humans simply do not look for new ways to solve a puzzle cannot entirely explain these results. To illustrate this, Watzek refers to some earlier studies that used similar tasks. In these, the researchers played participants a video explaining the potential shortcut.

"More of the humans do take the shortcut after seeing a video of somebody taking the shortcut," she says, "but about 30% still don't. In another version, we told them they shouldn't be afraid to try something new. More of them did use the shortcut then, but many of them still didn't."

The results are interesting, but as always, there is still much to learn. Study co-author Prof. Sarah Brosnan concludes that the study adds "to the larger body of literature on why humans can be so different from other primates."