Like humans, chimpanzees can rise to the occasion in front of a large audience or fail miserably, scientists said.

The team performed an experiment on six chimpanzees that have learned to use numerals at Kyoto University’s Center for the Evolutionary Origins of Human Behavior, previously known as the Primate Research Institute.

Over six years, the researchers from Kyoto University and Akita Prefectural University analyzed the records of how the six chimps tackled three numerical tasks of different degrees of difficulty in front of various groups.

Their study found that when more researchers were present, the chimps’ performance levels improved for the most difficult task but worsened for the easiest task.

“Our study has demonstrated there are ‘audience effects’ to a certain extent in chimpanzees as well,” said Shinya Yamamoto, a Kyoto University associate professor of comparative cognitive science, who was on the study team.

“We will continue exploring why the chimpanzees care about watching eyes and whether the same effects exist in other animal species as well.”

The audience effect can be seen in humans.

Certain baseball players, for example, seem to live for the moment when packed crowds are screaming during critical moments. But other players appear to cave in to the pressure and fail to exert their full powers.

The phenomenon shows that people care about their reputations and how others view them.

The researchers investigated if chimpanzees, the closest relatives of humans, also had an audience effect.

The study, from 2009 to 2015, covered 9,219 sessions, each consisting of 50 to 90 trials of the six chimps tackling the three numerical touchscreen tasks.

In the easiest task, numerals in an adjacent chain, such as 1, 2, 3 and 4, were shown at random on the screen. The chimpanzees were assigned to touch them in ascending order, like 1, 2, 3 and 4.

In the task of intermediate difficulty, numerals in a nonadjacent chain, such as 1, 3, 4, 6 and 9, were shown randomly on the monitor. The chimps were assigned to press them, again in ascending order, like 1, 3, 4, 6 and 9.

The most difficult task also involved a nonadjacent chain of numerals shown at random. However, when the initial, smallest number was pressed, the other numerals became hidden, so the chimps had to memorize the locations of the numbers before they could touch them.

The chimpanzees were given a piece of apple as a reward for a correct response.

The humans who attended the task scenes were categorized into three types: (1) one to five researchers, or experimenters, directly involved in this experiment on a daily basis; (2) zero to six familiar audience members who were not directly involved in the experiment; and (3) zero to five unfamiliar audience members from the outside.

The team analyzed how the number and types of the audience members affected the chimpanzees’ performances.

For the most difficult task, the correct answer rate improved with an increasing number of attending experimenters, the type of people closest to the chimps.

The ratio of correct responses was estimated to rise by 2 to 6 percent whenever the number of experimenters increased by one.

The correct answer ratio for the easiest task, by contrast, dropped with a rise in number of either experimenters or familiar audience members. The rate fell by 6 to 11 percent per increase of one in experimenter count and by 1 to 10 percent per increase of one in familiar audience count.

The number of observing strangers had no statistically significant impact on the chimps’ performance levels, regardless of the task type.

The researchers hypothesized that being watched by a large number of familiar people led the chimpanzees to place higher value on the solution of a difficult task. Therefore, they performed better.

But in the same situation, when facing the easy task, the chimps seemed distracted, and their performance level dropped.

“Humans under the watching eyes of colleagues care more about how the others will rate them,” Yamamoto said. “That can work as (negative psychological) pressure in some cases but can help improve performance in other situations.”

He continued: “The chimpanzees, who can tell familiar people from strangers, possibly underwent certain psychological changes, which manifested themselves in the form of the different performance levels.”

The research paper is available at: (https://www.cell.com/iscience/fulltext/S2589-0042(24)02416-7).