At least one species of primate underperforms when the heat is on

The world of sports is full of people who choke under pressure in very visible and humiliating ways. But as it turns out, humans aren't the only species capable of underperforming when the stakes are high, new research shows.

A team of scientists recently published a paper suggesting that at least three rhesus monkeys will, in fact, choke under pressure. The authors told Ars that this lapse in performance is almost certainly true of all rhesus monkeys—and quite possibly other primates as well.

There are several reasons you might expect a person—or a monkey—would fold under pressure. The researchers list social incluence, fear of losses, and over-excitement as some examples. So they decided to check if the size of a reward, which would increase the pressure, impacted a monkey's performance. When the reward was particularly large, the monkeys performed the task less well compared to more reasonably sized prizes.

“When it matters the most, you don't seem to perform the best,” Steven Chase, a professor of biomedical engineering at Carnegie Mellon University and one of the authors of the paper, told Ars.

Monkeying around

To check whether other primates would choke when the stakes are high, the team studied the actions of three rhesus monkeys. They put a monkey in an isolated room with a screen and attached a ring with an infrared tracker in it to one of the monkey's fingers. The motion capture system caused the movement of the monkey's finger to move a cursor on the screen.

For months, the researchers trained the monkeys in a task that would test their speed and accuracy. An alert would show up on the screen, telling the monkey that the test was about to begin, and the monkey would keep the cursor in the middle of the screen. A secondary target would then appear elsewhere on the screen, and the monkey would need to move the cursor to it before a set amount of time elapsed. If the monkey succeeded, it would get a reward: either water or fruit juice, depending on the monkey's preference.

“We felt that the intersection of motivation and performance would come to a head in a single action that was as brief in time as [possible],” Aaron Batista, a professor of bioengineering at the University of Pittsburgh and one of the authors of the paper, told Ars.

After the monkeys had been sufficiently trained, the researchers ran the experiment again, 10 times per animal. This time, however, the rewards were variable. Before each test, the monkeys received a visual cue indicating potential prizes—small, medium, large, and “jackpot,” which was 10 times the size of the medium reward.

They found that the monkeys generally performed the tasks better as the prizes increased. However, in the case of jackpot rewards—which came infrequently—the monkeys caved under pressure. Their speed and accuracy declined by between 10 and 25 percent compared to when they were performing for large rewards. The monkeys undershot the target and then spent extra time trying to edge their finger closer to it.

One of the monkeys also performed another experiment—roughly the same as the previous one. In this case, however, the monkey had to keep its cursor within a set path on the screen without overshooting its boundary. This monkey also choked when the heat was on.

Give athletes a break

It takes a long time—a matter of months—to train monkeys to perform these experiments. Additionally, there are strict animal welfare rules regulating the use of monkeys in experiments. As such, the team was only able to study this phenomenon in three rhesus monkeys. However, according to Batista, it's likely that other rhesus monkeys outside the lab also choke under pressure.