Such studies have nonetheless been met with skepticism when it comes to interpreting the behavior as evidence of animals’ ability to engage in make-believe. For instance, it’s possible the animals are responding to behavioral cues, like the direction of a gaze, to solve such tasks.

“Kanzi, let’s play a game!”

Enter Kanzi, a 43-year-old bonobo who lives at the Ape Initiative and is capable of responding to verbal prompts, either by pointing or using a lexigram of more than 300 symbols. There had also been anecdotal observations of Kanzi engaging in pretense. Krupenye et al. conducted three distinct experiments with Kanzi, each involving an 18-trial session.

In the first experiment, a scientist would offer a verbal prompt: “Kanzi, let’s play a game! Let’s find the juice!” They would then place two empty transparent cups on a table and pretend to fill them from an empty transparent pitcher, with another verbal prompt (“Kanzi, look!”). The scientist would pretend to pour the “juice” in one of the cups back into the pitcher, placing the pitcher under the table. Then they asked, “Kanzi, where’s the juice?” and recorded which cup the bonobo pointed to first.

“If Kanzi could only track reality (that both cups were empty), he should have chosen at chance between the two options, whereas if his choices were guided by stimulus enhancement, he should have selected the incorrect cup that had been ‘emptied’ above chance,” the authors wrote. “In contrast, if Kanzi could represent the pretend juice, he should have chosen above chance the cup containing the ‘imaginary’ juice, the empty cup that had not been ‘poured’ back into the pitcher. That is exactly what Kanzi did.” Kanzi selected the correct cup 34 out of 50 times (68 percent).