Scientists Find Apes Can Imagine, Challenging What Makes Humans Unique

For the first time, scientists have shown in a controlled experiment that apes can imagine things that aren't real. The finding came from a series of unusual tea parties with Kanzi, a bonobo who died last year at age 44, and it suggests that one of humanity's defining mental abilities may not be unique to us after all.

Researchers at Johns Hopkins University and the University of St. Andrews in Scotland designed simple experiments where they pretended to pour juice into cups and asked Kanzi to track the imaginary liquid. The results, published in the journal Science in early February, show that Kanzi understood the difference between what was real and what existed only in imagination.

Background

For decades, scientists believed that the ability to imagine—to hold two ideas in your mind at once and understand that something can be both real and not real at the same time—belonged only to humans. Children develop this skill early. By age two, a cardboard box becomes a spaceship. An empty cup holds pretend tea. Dolls become babies. Entire worlds run on nothing but agreement and imagination.

But apes, even the clever ones, were thought to lack this capacity. They could imitate. They could use tools. They could learn symbols and communicate with humans. Yet imagination seemed to exist on a different level—something tied to language, culture, and uniquely human creativity.

Kanzi was no ordinary bonobo. Raised in captivity at the Ape Initiative in Des Moines, Iowa, he learned to communicate using graphic symbols called lexigrams, combining them in ways that created new meanings. He also learned to make simple stone tools. His abilities already put him in rare company among animals.

Key Details

How the Experiment Worked

Christopher Krupenye, a cognitive scientist at Johns Hopkins, and Amalia Bastos, a comparative psychologist at the University of St. Andrews, modeled their tests on methods used with human children since the 1980s. They set up what they called a pretend tea party.

In the main experiment, they placed two empty, transparent cups on a table. Using an empty pitcher, they pretended to pour juice into both cups. Then they picked up one cup and pretended to pour the imaginary juice back into the pitcher. They asked Kanzi which cup still held the juice.

Kanzi pointed to the correct cup about 68 percent of the time—well above what would be expected by chance. The researchers repeated the test with real juice to confirm Kanzi could tell the difference. When one cup actually contained orange juice and the other held only pretend juice, Kanzi chose the real juice nearly 80 percent of the time.

A third test using pretend grapes produced similar results, suggesting Kanzi wasn't just lucky or responding to visual cues. He appeared to be tracking something that existed only in his mind.

"What's really exciting about this work is that it suggests that the roots of this capacity for imagination are not unique to our species." — Christopher Krupenye, Johns Hopkins University

Questions Remain

Not all scientists are convinced the findings prove what researchers claim. Michael Tomasello, a psychologist at Duke University, argues that choosing between imagined outcomes may not equal full pretend play. Stronger evidence, he suggests, would involve Kanzi actively creating the pretense himself rather than just responding to it.

Other researchers note that Kanzi was not a typical bonobo. Raised among humans from birth, he had experiences no wild bonobo would ever have. His unusual upbringing may have given him abilities that other members of his species don't possess.

What This Means

The implications of the research extend beyond one remarkable ape. If Kanzi could imagine, the capacity likely existed in the common ancestors that humans and great apes share—ancestors that lived six to nine million years ago. This suggests imagination is not a recent human invention but an ancient skill that evolved before our species even existed.

For decades, scientists have observed young female chimpanzees in the wild carrying sticks or logs and treating them like babies. Young bonobos have done similar things. But researchers could never be certain whether these animals were truly pretending or simply imitating behavior they had seen. This study provides the first hard evidence that at least one ape could hold an imaginary world in its mind.

Kristin Andrews, a philosophy professor at City University of New York who studies animal cognition, says the work opens new questions. Great apes appear to have the capacity to hold alternative representations in their minds. It's possible, she suggests, that other animals can too.

For species facing extinction, understanding how their minds work may matter more than ever. Bonobos are endangered, with fewer than 20,000 remaining in the wild. If their mental lives are richer and more complex than scientists previously thought, it changes how we should think about protecting them.

Kanzi died last year at 44, but researchers say his legacy extends far beyond his individual life. He opened a door to new questions about what goes on inside the minds of our closest living relatives.