The pressure of a watching audience can have positive or negative effects on human performance, and it turns out the same is true for our closest relatives.

Christen Lin at Kyoto University, Japan, and colleagues tested a group of six chimpanzees housed at the university’s primate research institute on three numerical tasks of varying difficulty.

In the first task, the numbers 1 to 5 appeared on the screen in random locations and the chimpanzees simply had to touch the numbers in the correct order to get a food reward.

In the second task, numbers were not adjacent: for example, 1, 3, 5, 7, 11 and 15 could appear on the screen. Again, the chimpanzees had to press numbers from smallest to largest to receive a reward.

Finally, in the most difficult test, when the first number in the sequence was pressed, the other numbers were hidden behind checkerboard squares on the screen. This meant that the chimpanzees had to memorize the location of the numbers in order to press them in the correct order.

The chimpanzees were tested on these tasks thousands of times over a six-year period with varying audiences – from one to eight human observers, some familiar to the chimpanzees and others new.

When the task was easy, the chimpanzees performed less when there were more people watching them. But on the most difficult task, all six chimpanzees did better as the audience grew.

“It was very surprising to see a significant increase in performance as the number of human experimenters increased, because we might expect the presence of more humans to be more distracting,” says Lin. “However, the results suggest that it might actually motivate them to perform even better.”

“For the easier task, humans may distract them, but for the harder task, it’s possible that humans are a stressor that actually motivates them to perform better.”

Team Member Shinya Yamamotoalso at Kyoto University, says he was very surprised to see this effect in chimpanzees.

“Such an audience effect is often thought to be unique to humans, who live in a normative, reputation-based society, in which we sometimes perform better in front of an audience and sometimes worse than expected,” he says. “But our study shows that this audience effect may have evolved in the ape lineage before the development of this type of normative society.”

Yamamoto says it is difficult and sometimes dangerous to draw direct implications for humans from non-human studies. “But, in an informal way, we might be able to ease the tension of those who are extremely nervous in public by saying that chimpanzees are the same!”

Miguel Llorente at the University of Girona, Spain, suggests that further studies could explore how the audience effect relates to chimpanzees’ individual personalities.

“It would also be fascinating to explore these effects with an audience of chimpanzees to better understand how these dynamics play out in a natural social context in order to generalize these findings to natural chimpanzee behavior,” he says.