The Mind-Reading Apes: Bonobos Adjust Their Communication Based on Human Knowledge
New research challenges our assumptions about theory of mind in nonhuman primates.
Do Bonobos Know What You Know?
For years, primatologists have debated whether our closest relatives, the great apes, possess a "theory of mind"—the ability to infer what others know or don’t know. While chimpanzees have shown signs of understanding another’s perspective, the question has remained unresolved for bonobos. A new study published in PNAS1 by Luke Townrow and Christopher Krupenye brings fresh evidence to the table, suggesting that bonobos can recognize ignorance in others and strategically alter their communication to compensate for it.
The implications of this discovery extend far beyond bonobo behavior. If our primate cousins can perceive and act upon the knowledge states of others, it challenges the long-held assumption that only humans possess this level of social cognition. The findings suggest that key components of theory of mind—previously considered uniquely human—may have been present in our common ancestor with bonobos and chimpanzees, dating back at least six million years.
“These findings suggest that apes can represent (and act on) others’ ignorance in some form, strategically and appropriately communicating to effectively coordinate with an ignorant partner and change his behavior.”
A Clever Experiment with an Age-Old Question
The Setup: A Simple Game of Cups
The experiment was designed around a cooperative task, in which bonobos had to help a human partner find a hidden food reward. The setup was straightforward: a researcher placed a treat under one of three cups while the bonobo observed. To get the treat, the bonobo had to rely on a second human partner, who would retrieve and hand over the food—if they knew where to look.
But here’s where things got interesting. In some trials, the human had watched the food being hidden, meaning they should know its location. In other trials, an opaque barrier prevented them from seeing where the treat was placed, rendering them completely ignorant of its location. The bonobos’ task? To decide whether or not to point to the correct cup, depending on what their human partner knew.
“If bonobos can represent a partner’s ignorance and are motivated to communicate based on this mental state attribution, they should point more frequently, and more quickly, to the hidden food’s location when their partner is ignorant than when he is knowledgeable.”
The Results: Bonobos Are Selective Communicators
The study found that bonobos were significantly more likely to point—and to do so more quickly—when their human partner was ignorant about the location of the food. When the human had seen where the treat was hidden, the bonobos were much less likely to point, suggesting that they understood when their help was needed.
Interestingly, the bonobos’ accuracy remained high regardless of the human’s knowledge state. This indicates that they were not just randomly pointing but were deliberately choosing to communicate based on their partner’s level of awareness.
“This suggests that apes are able to hold two conflicting representations in parallel—one that reflects the true nature of the world and another that does not.”
This ability to recognize another’s ignorance and take action to address it is a crucial feature of advanced social cognition. It suggests that bonobos can represent what others do not know—something that many previous studies had failed to confirm in nonhuman primates.
Why This Matters for Understanding Ape Intelligence
Challenging the Awareness Hypothesis
For decades, some researchers have argued that great apes don’t truly understand others' mental states but instead rely on simpler cognitive strategies. The “awareness hypothesis” suggests that apes track what others can see but do not actually grasp the concept of knowledge or ignorance in a human-like way.
Townrow and Krupenye’s results challenge this interpretation. The bonobos weren’t just responding to visual cues—they were selectively adjusting their behavior based on what their human partner had or had not experienced. This is a much more complex ability, one that suggests a deeper understanding of social dynamics.
“These results challenge prominent accounts arguing that apes track others’ epistemic states without any attention to their own knowledge of the situation.”
Bonobos vs. Humans: The Evolutionary Puzzle
The fact that bonobos show this ability raises intriguing evolutionary questions. Did our last common ancestor with bonobos and chimpanzees already possess a rudimentary theory of mind? If so, why did this ability develop to such extraordinary levels in humans while remaining limited in other apes?
One possibility is that while bonobos can recognize ignorance in specific, structured contexts—like this experiment—they do not use this skill as broadly or flexibly as humans do. Human theory of mind allows us to imagine entire belief systems, predict future behavior, and manipulate social dynamics on a grand scale. Bonobos, by contrast, may only apply this ability in direct, goal-oriented interactions.
“A critical question for future research is whether apes use theory of mind with the goal of changing their partner’s mental state or only their partner’s behavior.”
A Step Toward Understanding Primate Minds
Townrow and Krupenye’s study marks an important step in our quest to understand the minds of nonhuman primates. By showing that bonobos can recognize and respond to ignorance, it expands our understanding of primate intelligence and highlights the evolutionary roots of our own social cognition.
The research also paves the way for future studies that could explore whether bonobos use theory of mind in more complex ways. Can they recognize false beliefs—situations where another individual holds an incorrect assumption about the world? Do they adjust their communication strategies depending on social hierarchies or relationships? These are the next big questions for primatologists to tackle.
For now, though, this study offers compelling evidence that bonobos are not just passive observers of the world. They are active communicators, capable of adapting their behavior based on the minds of those around them.
“Some of the hallmark cognitive abilities that subserve uniquely human coordination and cooperation are within the cognitive potential of our closest relatives, and likely to be evolutionarily ancient.”
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Townrow, L. A., & Krupenye, C. (2025). Bonobos point more for ignorant than knowledgeable social partners. Proceedings of the National Academy of Sciences of the United States of America, 122(6). https://doi.org/10.1073/pnas.2412450122