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Watching young children host a make-believe tea party, with invisible tea and imaginary cookies, is a classic part of childhood. This type of imaginative play has long been considered an ability found only in humans. However, a new study published in the journal Science presents evidence that a bonobo named Kanzi can also take part in a pretend scenario, like a tea party. The researchers from Johns Hopkins University believe this suggests apes can use their imagination in a way similar to human toddlers.
“It really is game-changing that their mental lives go beyond the here and now,” said co-author Christopher Krupenye. “Imagination has long been seen as a critical element of what it is to be human, but the idea that it may not be exclusive to our species is really transformative. Jane Goodall discovered that chimps make tools, and that led to a change in the definition of what it means to be human, and this, too, really invites us to reconsider what makes us special and what mental life is out there among other creatures.”
According to the researchers, by around age two, human children can understand and navigate imaginary situations. A child can pretend there is real tea in a cup, even though it is actually empty. From a cognitive science perspective, this is an example of something called secondary representation. This means a person can hold two different ideas in mind at the same time: the imagined reality (the cup is full of tea) and the actual reality (the cup is empty).
Scientists have long wondered if other animals, particularly our primate relatives, also possess this mental ability. There has been some scattered and informal evidence to suggest they might. For example, a young chimpanzee was once seen dragging imaginary blocks across a floor, just as it did with real wooden blocks. In the wild, some female chimpanzees have been observed carrying and playing with sticks as if they were infants, which is a simple form of playing with a doll. A 2006 study also found that chimps and bonobos raised around human culture sometimes performed pretend actions, like holding a bowl to a doll’s mouth to feed it, when asked to do so.
Still, scientists have been cautious about interpreting these behaviors as clear proof of an animal's ability to engage in make-believe. It is possible, for instance, that the animals are simply responding to subtle behavioral cues from a human, like the direction of their gaze, rather than truly imagining a different reality.
This is where Kanzi, a 43-year-old bonobo, becomes important. Kanzi lives at the Ape Initiative research center. He is famous for his ability to understand spoken English and communicate by pointing or by using a special keyboard with more than 300 symbols, called a lexigram. Researchers had informally noticed Kanzi engaging in what looked like pretend play before. To investigate this scientifically, Krupenye and his team designed three separate experiments for Kanzi.