A bonobo named Kanzi has demonstrated the ability to engage in make-believe play, a cognitive skill previously unseen in non-human primates. In experiments conducted shortly before his death, Kanzi participated in a pretend tea party involving imaginary juice and grapes. The findings suggest that our closest primate relatives possess the capacity for imagination.
Kanzi, a bonobo born in the United States in 1980, lived most of his life at the Ape Initiative in Des Moines, Iowa. Renowned for his language skills, he communicated by pointing at symbols on a board. Kanzi passed away at age 44 in March 2023.
In the year prior to his death, researchers led by Amalia Bastos at the University of St Andrews in the UK tested Kanzi's ability to form "secondary representations"—the capacity to imagine alternative realities and share pretense, a skill young human children develop around ages 2 to 3. As Bastos explained, children at that age can track imaginary liquid poured between containers, a scenario replicated for Kanzi.
The first experiment involved researchers pretending to pour non-existent juice into two empty cups, then emptying one, and asking Kanzi to choose. Over two-thirds of the time, he selected the cup that appeared to still hold the pretend juice. "If Kanzi hadn’t conceived of ‘imaginary juice’ in the cups throughout the study, he should have picked between the two cups at chance—after all, they were both empty," Bastos noted.
Control tests confirmed Kanzi's distinctions: he chose a cup with real juice over an empty one more than three-quarters of the time and always picked a cup with a real grape. In a pretend grape scenario, he again correctly chose over two-thirds of the time. All sessions were voluntary, and Bastos observed that Kanzi's continued participation suggested he enjoyed the activities.
Experts praised the study. Gisela Kaplan at the University of New England in Australia called it "unambiguous that the bonobo has understood the pretense and is entering into the game," likening it to children's dollhouse play. Miguel Llorente at the University of Girona in Spain dubbed Kanzi the "Einstein of his species" and proposed that his exposure to human interaction unlocked latent imaginative abilities, potentially tracing back to a common ancestor 6 to 9 million years ago.
The research appears in Science (DOI: 10.1126/science.adz0743).
