For decades, imagination and pretend play were viewed as abilities that belonged only to humans. New research now suggests our closest relatives may share that skill.

Scientists have reported the first experimental evidence that an ape can engage in make-believe. The study, published in the journal Science, found that a bonobo named Kanzi appeared to track imaginary objects during structured play tasks, showing signs of pretend thinking.

The findings indicate that imagination may not be exclusive to humans and could date back to a shared ancestor millions of years ago.

“This is one of those things that we assume is distinct about our species,” said Christopher Krupenye, a cognitive scientist at Johns Hopkins University and an author of the study.

“This kind of finding really shows us that there’s much more richness to these animals’ minds than people give them credit for,” he said.

Testing pretend thinking

Researchers already knew apes could form mental pictures of hidden items. For example, if food is placed under a cup, an ape can remember where it is even when it cannot see it. That skill relies on memory and expectation.

The new experiments went further by testing whether an ape could treat something imaginary as if it were real.

“This kind of work goes beyond it,” Krupenye said. “Because it suggests that they can, at the same time, consider multiple views of the world and really distinguish what’s real from what’s imaginary.”

To test this, Krupenye and Amalia Bastos, a cognitive scientist at the University of St. Andrews, worked with the Ape Initiative in Iowa. Their subject was Kanzi, a well-known bonobo raised in captivity who became famous for understanding spoken English and communicating with symbols.

The “tea party” experiments

The team designed simple play scenarios that resembled children’s pretend games.

In one test, a researcher pretended to pour juice into two empty cups and then poured one cup back into a jug. If Kanzi followed the imaginary liquid, one cup would still “contain” juice. When asked where the juice was, Kanzi pointed to the correct cup more often than random guessing would predict.

In another task, one cup held real juice and the other only imaginary juice. Kanzi chose the cup with real liquid, showing he could separate fantasy from reality.

A third setup used imaginary grapes moved between bowls. Again, Kanzi selected the bowl that should have held the pretend fruit more than half the time.

Independent scientists said the results were striking.

“It’s so fascinating to get such clear evidence of imagination,” said Joseph Feldblum, an evolutionary anthropologist at Duke University who was not involved in the research. “These experiments are able to peel back the layers and understand a lot more about what’s actually going on inside their minds.”

Why imagination matters

In humans, imagination helps people rehearse events, plan decisions, and solve problems before acting. Children use pretend play to practice real-life situations.

Researchers think apes might benefit in similar ways, such as exploring possible outcomes or trying different strategies mentally before acting.

“There are many benefits to not being stuck in the here and now,” Bastos said, “because you can start thinking about alternative futures.”

Clues about human evolution

Bonobos and chimpanzees are humans’ closest living relatives. Scientists believe all three species share a common ancestor that lived millions of years ago. Discoveries like this suggest that some mental abilities thought to be uniquely human may have deeper evolutionary roots.

Field researchers have observed playful behaviors in wild bonobos before, such as carrying sticks like dolls. The new laboratory tests offer clearer proof that such actions may reflect true imagination rather than simple habit.

Questions remain about how and why this ability developed. Researchers hope future studies with more animals will help explain when pretend thinking emerged and what role it plays in ape behavior.

For now, the study adds to growing evidence that the mental lives of apes may be more advanced than once believed.