Can apes play pretend? Scientists use an imaginary tea party to find out

By age 2, most kids know how to play pretend. They turn their bedrooms into faraway castles and hold make-believe tea parties. The ability to make something out of nothing may seem uniquely human—a bedrock of creativity that's led to new kinds of art, music, and more. Now, for the first time, an experiment hints that an ape in captivity can have an imagination. "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," said study co-author Christopher Krupenye with Johns Hopkins University. Kanzi is a bonobo who was raised in a lab and became a whiz at communicating with humans using graphic symbols. He combined different symbols to make them mean new things and learned how to create simple stone tools. Scientists wondered whether Kanzi had the capacity to play pretend—that is, act like something is real while knowing it's not. They'd heard reports of female chimpanzees in the wild holding sticks as though they were babies and chimps in captivity dragging imaginary blocks on the ground after playing with real ones. But imagination is abstract, so it's hard to know what's going on in the apes' heads. They could just be imitating researchers or mistaking imaginary objects for the real thing. Researchers adapted the playbook for studying young children to stage a juice party for Kanzi. They poured imaginary juice from a pitcher into two cups, then pretended to empty just one. They asked Kanzi which cup he wanted, and he pointed to the cup still containing pretend juice 68% of the time. To make sure Kanzi wasn't confusing real with fake, they also ran a test with actual juice. Kanzi chose the real juice over the pretend almost 80% of the time, "which suggests that he really can tell the difference between real juice and imaginary juice," said Amalia Bastos, a study co-author from the University of St. Andrews in Scotland. But not all scientists are convinced that Kanzi is playing pretend like humans do. There's a difference between envisioning juice being poured into a cup and maintaining the pretense that it's real, said Duke University comparative psychologist Michael Tomasello.