A chimpanzee tackles a number test on a touch screen
Akiho Muramatsu
Audience pressure can have positive or negative effects on human performance, and the same is true of our closest relatives.
Christen Lin At Kyoto University, Japan, and colleagues at the university’s primate research institute tested a group of six chimpanzees on three numerical tasks of varying difficulty.
In the first task, the numbers 1 to 5 appeared in random locations on the screen and the chimpanzees had to touch the numbers in the correct order to get a food reward.
In the second task, the numbers were not adjacent: for example, 1, 3, 5, 7, 11, and 15 could appear on the screen. Again, the chimpanzees had to click from smallest to largest to receive a reward.
Finally, in the hardest test, when the first number in the sequence was pressed, the remaining numbers were hidden behind checkered boxes on the screen. This meant that the chimps had to memorize the location of the numbers in order to be able to press them in the correct order.
The chimps were tested thousands of times over a six-year period with a variety of observers: from one to eight human observers, some familiar to the chimps and some new.
When the task was easy, the chimps did worse when more people were watching. But on the most difficult task, the six chimpanzees did better as the size of the listeners increased.
“It was very surprising to find a significant increase in performance as the number of human experimenters increased, because we would expect the more humans present to be more distracting,” says Lin. “However, the results suggest that this can motivate them to perform even better.
“For the easiest task, it allows humans to be distracted, but for the most difficult task, it may be a stressor that motivates humans to perform better.”
Team member Shinya YamamotoAlso at Kyoto University, he says they were very surprised to find this effect in chimps.
“Such an audience effect is thought to be unique to humans, who live in a normative reputation-based society where we sometimes perform better in front of an audience and sometimes perform worse than expected,” he says. “But our study shows that this bystander effect may have evolved in the ape lineage before this type of social regulation developed.”
Yamamoto says it is difficult and sometimes dangerous to draw direct conclusions for humans from non-human studies. “But, by chance, we will be able to ease the tension of the very nervous public by saying that chimpanzees are the same!”
Miguel Llorente at the University of Girona, Spain, suggests that further studies may be conducted into how the bystander effect relates to chimpanzees’ individual personalities.
“It would also be fascinating to study these effects with chimpanzee audiences to better understand how these dynamics play out in a natural social context, to generalize these results to natural chimpanzee behavior,” he says.
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