KYOTO (Kyodo) -- Chimpanzees are better able to solve complex exercises when they are being watched by those familiar to them, such as researchers in an experiment, a recent Japan-based study has showed.

The report by researchers at Kyoto University and Akita Prefectural University, published in U.S. science journal iScience, also said chimpanzees perform worse at simpler problems when watched by an audience.

Although it is not well understood whether animals other than humans change behavior knowing others are watching -- known as the "audience effect" -- Shinya Yamamoto, a Kyoto University associate professor of comparative cognitive science, said, "If chimpanzees care about who is looking at them, then the audience effects seen in human society may have existed in apes as well."

The research involved monitoring six chimpanzees at the university's Center for the Evolutionary Origins of Human Behavior over six years. The primates completed sets of 50 to 90 tasks a day while being watched by others.

Observers were split into three groups; those actively involved in the experiment, those not involved directly but known to the chimpanzees such as their caretakers, and complete strangers, to see whether such groupings made a difference.

In the most difficult task, which entailed numbers being randomly placed on a screen for the chimpanzee to remember, results were most successful when they were grouped with observers involved in the experiment.

The chimpanzees were given a piece of apple for every number they remembered correctly. It is possible that the chimps valued food rewards more when others were around them, according to the November report.

On the other hand, the simplest exercise which involved pushing numbers in order, the chimpanzees performed worse with groups they were familiar with.

It is believed the familiar observer's presence caused the chimpanzee to become distracted and stressed.

In both exercises the presence of unknown observers appeared to have no effect on results.