For decades, imagination occupied a near-sacred place in the definition of what it means to be human. The ability to pretend, to play that an empty cup contains tea, or that a nonexistent fruit can be moved from one container to another, formed part of the cognitive repertoire that separated our species from the rest of the animal kingdom.
However, a series of experiments conducted by researchers at Johns Hopkins University and the University of St Andrews is challenging that boundary with results that are both simple and disruptive. The central figure in this research is Kanzi, a bonobo known for his cognitive abilities and capacity for communication.
The study, published in Nature, was inspired by observations of early childhood development in humans. Young children engage in pretend play with remarkable naturalness, drinking from empty cups or caring for imaginary patients. This type of symbolic play is considered an early signal of imagination and a developing mental life that extends beyond the immediate present. Until now, no controlled study had conclusively demonstrated a comparable ability in non-human animals.
Researchers, led by Christopher Krupenye and Amalia Bastos, designed experiments to address this gap. The core setup involved Kanzi and a human experimenter facing each other across a table. The researchers presented empty jars, cups, bowls, and containers, creating a scenario reminiscent of a children’s tea party. The goal was to observe whether Kanzi could follow the trajectory of objects that didn’t physically exist.
In a key experiment, the researcher simulated pouring juice into two transparent glasses and then pretended to empty one of them. The question posed to Kanzi was simple: where was the juice? Consistently, Kanzi pointed to the correct glass, even when the experimenter changed the position of the containers. To rule out the possibility that Kanzi was responding to subtle, imperceptible cues, the team introduced a second test involving real juice and imaginary juice. Kanzi overwhelmingly chose the glass with actual juice, demonstrating an understanding of the difference between the real and the imagined.
The same approach was repeated with imaginary grapes being moved between containers. Again, Kanzi correctly identified the location of the nonexistent object. While not infallible, his performance significantly exceeded what would be expected by chance. Crucially, Kanzi received no rewards for correct answers, eliminating the possibility of learning based on subtle signals from the experimenter.
“It’s truly transformative to think that imagination is not unique to our species,” the researchers stated, suggesting a fundamental rethinking of what defines human cognition. The results indicate that Kanzi was able to maintain and update imagined states superimposed on immediate reality, a cognitive ability previously thought to be exclusive to humans.
The findings build upon anecdotal observations that have long hinted at pretend play in great apes. Researchers have previously observed chimpanzees interacting with imaginary objects, such as playing with invisible cubes or treating sticks as if they were dolls. However, these observations lacked the rigor of controlled experimental demonstrations. The work with Kanzi, according to Antonio J. Osuna Mascaró, a postdoctoral researcher at the Messerli Research Institute, “takes that step, showing that a bonobo can maintain and update imagined states superimposed on immediate reality.”
The implications of this research extend beyond primatology. It raises fundamental questions about the evolution of cognition and the origins of complex mental abilities. If a bonobo can comprehend and manipulate imaginary objects, the line between human and animal imagination becomes significantly blurred. The researchers propose that this capacity may date back to a common ancestor that lived between six and nine million years ago.
The study also echoes the landmark work of Jane Goodall, who revolutionized the understanding of chimpanzees by documenting their tool use. Goodall’s discovery forced a reevaluation of the definition of humanity, and this new research on Kanzi is prompting a similar reassessment. As Krupenye explained, “Jane Goodall discovered that chimps make tools and that led to a shift in the definition of what it means to be human, and this also invites us to reconsider what makes us special and what mental life is out there among other creatures.”
The research team acknowledges that Kanzi’s unique upbringing – raised in a research environment with extensive training in symbolic communication – may have contributed to his abilities. It remains unclear whether bonobos without such intensive interaction with humans would demonstrate similar skills. However, the study provides the first rigorous experimental evidence that a non-human animal can follow nonexistent objects within a simulated scenario.
Beyond the specific case of Kanzi, the work encourages a broader reflection on how we interpret the mental lives of animals. For a long time, the prevailing view was that animals lived anchored to the present, reacting almost automatically to external stimuli. These new data challenge that image. If a bonobo can hold in its mind the existence of a nonexistent object and simultaneously understand that it is not real, then the boundary between human and animal imagination becomes much more diffuse.
The findings also raise ethical considerations. If apes possess a richer mental life than previously believed, the human responsibilities toward their care and conservation take on new weight. Krupenye emphasized that “imagination is one of those things that in humans gives us a rich mental life. And if we share some roots of imagination with apes, that should make us question the assumption that other animals simply live robotic lives, limited to the present.”
Starting with a simple scene – a table with empty cups and gestures of fiction – scientists have opened an unexpected window into the minds of our closest evolutionary relatives. The game of simulation, so familiar in human childhood, appears as a cognitive bridge connecting species separated by millions of years of evolution. In this intersection, imagination ceases to be an exclusive privilege and becomes a shared heritage, still in the process of being understood.
