In a groundbreaking experiment, researchers at Johns Hopkins University have demonstrated for the first time that apes can communicate unknown information to humans in the name of teamwork. The experiment, conducted by Chris Krupenye, assistant professor of psychological and brain sciences, and Ph.D. student Luke Townrow, involved bonobos—a close relative of chimpanzees—and has provided the clearest evidence to date that apes can intuit another’s ignorance. This ability, once thought to be uniquely human, opens a new window into understanding the rich mental lives of non-human primates.
The study, published in Proceedings of the National Academy of Sciences, offers important insights into the theory of mind—the ability to understand that others have different beliefs, knowledge, and perspectives. This cognitive skill is essential for sophisticated social behaviors like cooperation, communication, and problem-solving, and it is often considered a hallmark of human intelligence. However, this research shows that some of these abilities are not exclusive to humans but are shared with other apes.
The Experiment: Understanding Ignorance and Communication
The experiment took place at Ape Initiative, a research and education nonprofit, with three male bonobos: Nyota (25 years old), Kanzi (43 years old), and Teco (13 years old). The bonobos were involved in a simple but revealing experiment designed to test their ability to understand another individual’s ignorance.
The setup was straightforward. One researcher, Townrow, would sit with the bonobo at a table, facing each other. A second person would then place a treat—either a grape or a Cheerio—under one of three cups, while Townrow watched. In some trials, Townrow was able to see where the treat was hidden; in others, he was kept in the dark about its location. The bonobo’s task was to guide Townrow to the correct cup where the treat was hidden, but only if he did not know the answer.
When Townrow knew where the treat was hidden, the bonobos remained still, waiting patiently for him to find it. However, when Townrow had no idea where the food was hidden, the bonobos would eagerly point at the correct cup—sometimes very insistently. In some cases, the apes would tap on the mesh separating them from Townrow, clearly trying to communicate and get his attention.
One bonobo in particular, Kanzi, known for being highly food motivated, demonstrated the most active communication behavior. He would tap multiple times on the mesh, almost pleading for Townrow to follow his lead. This behavior clearly indicated that the bonobos understood Townrow’s ignorance and were using this knowledge to guide his actions, showcasing their understanding of another individual’s lack of information.
Understanding the Theory of Mind
The findings suggest that bonobos, like humans, can track the knowledge state of others. Specifically, when their partner was unaware of the location of the treat, the bonobos pointed more often and more urgently. This behavior indicates that they can differentiate between their own knowledge and that of others, a core aspect of theory of mind.
“Their ability to track ignorance in others and act accordingly was striking,” Krupenye explained. “We predicted that if apes were truly sensitive to ignorance, they would point more frequently when their partner lacked knowledge, and that’s exactly what we observed.”
What’s particularly fascinating about this discovery is that it suggests apes can hold two conflicting perspectives in their minds simultaneously. They are aware of the correct answer—the location of the food—but they are also cognizant that their partner is ignorant of that information. This cognitive feat requires a sophisticated understanding of other minds, an ability thought to be unique to humans or at least highly developed in humans compared to other animals.
Implications for Understanding Apes’ Cognitive Abilities
This experiment provides significant evidence supporting the idea that apes are more cognitively sophisticated than previously believed. For years, scientists have debated whether non-human primates possess the cognitive foundations necessary for complex social behaviors like communication, teaching, and learning. Some have even denied that animals beyond humans have a true theory of mind. This research, however, challenges that view and suggests that humans and apes share a rich mental foundation that enables cooperative behavior, social communication, and strategic decision-making.
“This study is groundbreaking in that it shows how apes are able to communicate their understanding of what others know and don’t know,” said Krupenye. “For a long time, it was believed that this kind of awareness was unique to humans, but this study demonstrates that apes share these capacities with us, and they likely evolved millions of years ago in our common ancestors.”
The findings also add to growing evidence that apes use sophisticated social strategies in the wild. Similar behavior has been observed in wild chimpanzees and other primates, such as when they vocalize to warn others about potential threats like predators. In the case of the bonobos in the experiment, their ability to point out food and communicate about an individual’s ignorance mirrors the way chimpanzees use vocalizations to alert others to dangers.
The Next Steps: Understanding Motivation and Beliefs
While the current study provides compelling evidence of apes’ theory of mind, it also raises further questions about the nature of ape cognition. For example, the researchers are now interested in exploring the motivations behind these behaviors. Are the bonobos simply trying to help Townrow find the treat, or are they attempting to alter his beliefs or perceptions? Understanding whether apes use communication to change others’ mental states is an important next step in investigating the depth of their cognitive abilities.
Luke Townrow, the study’s co-author, explained, “What we’ve shown here is that apes are capable of changing a partner’s behavior by communicating their knowledge. But the big question moving forward is whether they are also trying to influence their partner’s beliefs—their mental state—about the situation.”
This question about whether apes are aware of the beliefs or intentions of others remains a critical avenue for future research. It will also be important to investigate whether apes demonstrate the ability to teach others, which would represent another advanced form of communication and knowledge transfer.
Conclusion: Implications for the Study of Animal Cognition
The research conducted by Krupenye, Townrow, and their colleagues has profound implications for our understanding of animal cognition. For decades, the belief has persisted that complex social behaviors like teaching, cooperative problem-solving, and language are uniquely human. This study, however, shows that some of these abilities are shared with our closest primate relatives.
The ability to understand another’s ignorance—and to communicate this awareness—is at the heart of our most sophisticated social behaviors. It is central to how we cooperate, share knowledge, and work together in both casual and strategic contexts. By recognizing that apes, too, have the capacity to engage in such behaviors, this research opens new doors for exploring the evolution of human-like cognition in animals.
As the study suggests, the rich mental lives of apes are far more complex than once thought, and their cognitive abilities may be far closer to those of humans than previously realized. Moving forward, researchers hope to deepen our understanding of these abilities, exploring not just how apes communicate but also how they understand and manipulate each other’s mental states.
This new evidence of social intelligence in bonobos may ultimately lead to a reevaluation of what makes humans unique. It may also encourage further exploration into the complex relationships between humans and non-human animals, helping us to better understand the cognitive foundations that underpin the most fundamental aspects of social interaction.
Reference: Townrow, Luke A., Bonobos point more for ignorant than knowledgeable social partners, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2412450122