Do chimps care when we watch them?

The more people watch you, the more pressure you feel, whether during a presentation, a performance, or a sports match; this is an experience we all understand.

But what about our closest relatives, the chimpanzees? Do they also feel pressure in front of an audience? And what if the audience consists of humans rather than fellow chimps?

A team of researchers at Kyoto University has now found some answers, using various number-based touch screen cognitive tasks — 9,219 sessions total, each consisting of 50–90 trials — performed by the chimps on a daily basis for over six years. Six chimpanzees took part, all living in KyotoU's Center for the Evolutionary Origins of Human Behavior in Aichi prefecture, formerly known as the Primate Research Institute.

The authors were surprised to find that, on the most difficult task, the chimpanzees' performance improved when more experimenters were present. This task involved rapid memorization of multiple numbers placed randomly around the screen, which became hidden when the chimps pressed the first number in the sequence.

"You wouldn't expect chimps to care that humans were watching them, much less to the extent that they actually do better on such a difficult task," says Christen Lin, the first author.

Conversely, on the easiest task, the chimps' performance decreased when more experimenters and familiar audience members were present. This task only required pressing numbers in the correct order. When tried again with people the chimps were not familiar with, however, there was no observable difference in performance.

"The chimpanzees' performance varied across audience types, and this audience effect varied with task difficulty too," continues Lin.

The authors' hypotheses are based on audiences affecting the chimpanzees' perception of reward values, since the chimps received food upon completion of each trial. Alternatively, audiences could have influenced the chimps' mental stress or concentration levels.

"Whether consciously or unconsciously, humans care much about being watched," says corresponding author Shinya Yamamoto.

"If chimps also care about audiences, especially about who is watching them, then it's possible that this characteristic arose in the great ape lineage before the formation of reputation-based societies in humans."