Chimpanzees perform complex tasks better when watched by humans, study finds

A new study conducted by researchers from Kyoto University has revealed that chimpanzees perform better on difficult tasks when they are observed by humans. Published in the journal iScience on September 8, the research evaluated the relationship between the presence of spectators and the performance of chimpanzees in cognitive tasks.

The phenomenon, known as the "audience effect," is a psychological concept where an individual's behavior changes if they believe someone is watching them. This effect can improve or weaken performance depending on various factors, such as the difficulty of the task and the individual's familiarity with the observers. Previously considered exclusive to humans, the audience effect has now been observed in chimpanzees, suggesting that this trait may have deeper evolutionary roots in great ape species.

The researchers aimed to explore whether non-human primates experience the audience effect. They analyzed data from over 2,100 sessions conducted over six years, involving six chimpanzees at the Primate Research Institute of Kyoto University. The chimpanzees participated in cognitive tasks using touchscreens to receive food rewards, allowing the researchers to study their behavior in a familiar context.

The experiments assessed the chimpanzees' performance under varying audience conditions. The number of human observers ranged from one to eight, including both familiar experimenters and unfamiliar individuals. The chimpanzees were placed in cages with glass walls, allowing them to see who was watching them during the tasks. Since the walls were transparent, the chimpanzees knew when they were being observed and by whom.

The tasks varied in difficulty and involved numerical sequences requiring the chimpanzees to touch numbers in order. In the simplest task, they had to touch numbers from 1 to 19 sequentially as they appeared in direct order. In the second task, the numbers appeared in random order, and the chimpanzees had to select them from disparate locations on the screen, pressing them from smallest to largest. In the most challenging task, after selecting the first number, the others were masked, requiring them to quickly memorize the positions in real-time.

The results showed that the chimpanzees performed better on the more difficult tasks as the number of observers increased, particularly when the observers were familiar to them. "Their performance increased in the most difficult task as the number of experimenters increased," explained lead author Christen Lin. "Whereas, in the easiest task, performance decreased as this type of observer increased."

Conversely, in the easiest task, the chimpanzees' performance decreased as the number of familiar observers increased, indicating that the presence of known individuals may have been distracting or added psychological pressure during simpler tasks. "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," Lin stated.

The findings suggest that chimpanzees adjust their performance based on the presence and number of human observers, much like humans do. "We were very surprised to find a significant increase in performance as human experimenter numbers increased, because we might expect more humans being present to be more distracting," Lin said. "The fact that they seem to be affected by human audiences even depending on the difficulty of the task suggests that this relationship is more complex than we would have initially expected."

Senior author Shinya Yamamoto added, "Our findings suggest that how much humans care about witnesses and audience members may not be quite so specific to our species." He explained that if chimpanzees also pay special attention to audience members while performing their tasks, "it stands to reason that these audience-based characteristics could have evolved before reputation-based societies emerged in our great ape lineage."

The researchers suggest that the audience effect in chimpanzees may be linked to similar social pressures that influence human behavior. The presence of familiar observers may increase motivation or encourage the chimpanzees to perform better on complex tasks. This indicates that the roots of the audience effect may be deeply embedded in the social evolution of primates.

However, the specific mechanisms underlying these audience-related effects remain unclear, even in humans. "It remains unclear what specific mechanisms underlie these audience-related effects, even for humans," the researchers noted. They believe that studying this phenomenon in other great apes may help understand how this trait evolved and why it arose. "This study opens the door to further research on the audience effect in other primates, which may help scientists gain a deeper understanding of the reasons behind the evolution of this social effect and how it has shaped over time," Yamamoto said.

The researchers also observed that the chimpanzees paid attention to who was among the human audience during the tasks. "According to our analysis, the unknown audience did not have a significant effect on performance, while the experimenters and the known audience did," Lin explained. This suggests that the presence of familiar individuals positively influences behavior, reinforcing the hypothesis that the behavior has an ancestral origin.

The study provides compelling evidence that chimpanzees, like humans, are influenced by the presence of an audience, adjusting their performance accordingly. This discovery challenges the notion that the audience effect is unique to humans and suggests that it may have deeper evolutionary origins shared among great apes.

"We might not have expected chimpanzees to care about the presence of another species watching them while performing the task," Lin added. "But the fact that they seem to be affected by the presence of an audience, especially when the task is difficult, opens the door to a deeper understanding of this effect."

The researchers hope that further studies of our ape relatives may help one day better explain these shared, cross-species experiences. "Studying this phenomenon in other great apes may help us understand how these behaviors evolve and why they arise," they concluded.

Sources: Asharq News, Popular Science, Agencia SINC, The Independent, ETV Bharat, ABC Color, Folha de S.Paulo, New Scientist, Science Daily, RPP Noticias, Sky News.

This article was written in collaboration with generative AI company Alchemiq