A chimpanzee tackling a number test on a touch screen
Akiho Muramatsu
The pressure of a watching audience can have positive or negative effects on human performance, and it turns out the same is true of our closest relatives.
Christen Lin at Kyoto University, Japan, and his colleagues tested a group of six chimpanzees housed at the university’s primate research institute on three numerical tasks with varying difficulty.
In the first task, the numbers 1 to 5 appeared on the screen in random locations and the chimps simply had to touch the numbers in the correct order to get a food reward.
In the second task, the numbers weren’t adjacent: for example, 1, 3, 5, 7, 11 and 15 might appear on the screen. Again, the chimps had to press the numbers from smallest to largest in order to receive a reward.
Finally, in the hardest test, when the first number in the sequence was pressed, the rest of the numbers were hidden behind chequered squares on the screen. This meant the chimps had to memorise the location of the numbers in order to press them in the correct order.
The chimps were tested on the tasks thousands of times over a six-year period with varying audiences – from one to eight human observers, some familiar to the chimps and others who were new.
When the task was easy, the chimps performed worse when there were more people watching. But on the most difficult task, all six of the chimps did better as the size of the audience grew.
“It was very surprising to find a significant increase in performance as human experimenter numbers increased, because we might expect more humans being present to be more distracting,” says Lin. “However, the results suggest that this may actually motivate them to perform even better.
“For the easiest task, the humans may be distracting to them, but for the most difficult task it is possible that the humans are a stressor that actually motivates them to perform better.”
Team member Shinya Yamamoto, also at Kyoto University, says they were very surprised to find this effect in the chimps.
“Such an audience effect is often thought to be unique to humans, who live in a reputation-based normative society, where we sometimes perform better in front of an audience and sometimes perform worse than we expected,” he says. “But our study shows that this audience effect may have evolved in the ape lineage before the development of this kind of normative society.”
Yamamoto says it is difficult and sometimes dangerous to draw direct implications for humans from non-human studies. “But, in a casual way, we may be able to ease the tension of those who are extremely nervous in public by saying chimpanzees are the same!”
Miguel Llorente at the University of Girona, Spain, suggests further studies could explore how the audience effect is related to chimpanzees’ individual personalities.
“It would also be fascinating to explore these effects with chimpanzee audiences to understand more fully how these dynamics play out in a natural social context in order to generalise these results to the natural behaviour of chimpanzees,” he says.
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