A recent study conducted by researchers at Johns Hopkins University revealed that bonobos have the ability to recognize ignorance in others, communicate to correct it, and cooperate accordingly, challenging the notion that theory of mind is exclusive to humans. The work was conducted by researchers with Johns Hopkins University's Social and Cognitive Origins Group, including doctoral student Luke Townrow and co-author Christopher Krupenye, and was published in the Proceedings of the National Academy of Sciences.
In the experiment, a bonobo sat face-to-face with Townrow at a table. Between them were three upturned plastic cups, under one of which a treat, such as a grape or a Cheerio, was hidden. The bonobo always observed as a second person hid the treat under one of the cups. Sometimes, Townrow saw where the treat was placed, and other times he did not. When Townrow asked, "Where is the grape?" and waited ten seconds, the bonobos would often point to the correct cup, especially when he had not seen where the treat was hidden.
In cases where Townrow had not seen under which cup the treat was hidden, the bonobos enthusiastically pointed to the hiding place, often doing so insistently and demonstratively. One of the bonobos, Kanzi, who was very motivated by food, repeatedly pointed in certain phases of the experiment, tapped several times to get the researchers' attention, and was quite insistent. "Their fingers pointed through the mesh; it was clear what they were trying to communicate," said Krupenye, a co-author of the study, adding, "Their fingers were literally piercing the mesh—it was obvious they were trying to say something," according to Phys.org.
"The ability to sense gaps in one another's knowledge is at the heart of our most sophisticated social behaviors, central to the ways we cooperate, communicate, and work together strategically," Krupenye stated. The study provides the clearest evidence to date that apes can intuit another's ignorance, a capacity previously thought to be exclusively human. When the person knew where the grapes were hidden, the bonobos waited calmly for the person to retrieve them.
"What we've shown here is that apes will communicate with a partner to change their behavior," said Townrow, but noted that a key question is whether apes also aim to change their partner's mental state or beliefs. The findings suggest that these capacities, including theory of mind, evolved millions of years ago in our common ancestors with apes.
"The results also suggest apes can simultaneously hold two conflicting world views in their mind. They know exactly where the food is, and at the same time, they know that their partner's view of the same situation is missing that information," Krupenye explained. This ability to understand another's ignorance is fundamental to how humans cooperate, communicate, and work together strategically, as it is key for effective communication and cooperation.
Bonobos (Pan paniscus) are one of the two species of chimpanzees and are the closest relatives of humans, known for their high level of social organization, peacefulness, and communication abilities. They inhabit only the forests of the Democratic Republic of the Congo and are known for their cognitive abilities that challenge our beliefs about communication and cooperation between species.
The team plans to explore more deeply the motivations of the primates and how they think about the minds of other individuals. The researchers acknowledge that it remains unclear whether the bonobos pointed to the grapes to prompt a correct action from their partner or simply to share information.
Recognizing informational gaps is an ability that was previously thought to be exclusive to humans. "We predicted that if apes are really tracking ignorance, when their partners lacked knowledge they would be pointing more often and more quickly and that's exactly what they did," Krupenye noted, according to Science Daily.
This article was written in collaboration with generative AI company Alchemiq