An eight-year-old juvenile chimpanzee named Kakama trudged along a path among the forest trees, following his pregnant mother. A scientist sat silently at a distance, watching Kakama pick up a log and carry it with him for hours. At one point, Kakama made a nest and placed the log in it, as if it were a small chimpanzee. Months later, two field assistants observed the same thing: Kakama was playing with a similar log, which they labelled "Kakama's toy baby."
Was Kakama simply confused? Did he really think that the log was a smaller version of himself? Or did Kakama know that the log was really a log, and was only pretending that the log was a baby?
Kanzi, the famous bonobo, liked to pretend as well. Primatologist Sue Savage-Rumbaugh described watching Kanzi hide invisible objects under blankets or leaves, later removing them from their hiding spots, and pretending to eat them. "Kanzi also engages the participation of others" in these games, Savage-Rumbaugh notes, "by giving them the pretend object and watching to see what they do with it."
From an early age, human children act out imagined scenes that conflict with reality. Psychologist Robert W Mitchell calls children "proto-typical pretenders", and he writes that pretend play, or make-believe, is "a mental activity involving imagination". Which is, admittedly, useless as a definition.
Dreams could be thought of as being one form of imagination. When researchers measured the brain activity of rats as they were learning to navigate a maze, they saw the same firing pattern while they were asleep as when they were awake. The rats were running through the mazes in their sleep – it was as if someone had pressed the rewind button on a brain activity recorder, and pressed play.
But pretending or "make believe" requires a bit more mental complexity than that. One kind of pretence involves imagining that one object, such as a banana, is actually a second type of object, such as a telephone, or imagining that a lifeless object such as a doll is actually animate – both of which were observed with Kakama.
Flights of fantasy
Another type of pretence involves imagining an object that isn't even there in the first place, such as when children (or adults) play air guitar. An illuminating example of this sort of imagination comes from a chimpanzee named Viki who was raised in a human home. Viki had lots of toys, including some attached to strings that could be pulled along. Primatologists Mary Lee Jensvold and Roger Fouts recount the original description of Viki's behaviour: "Very slowly and deliberately she was marching around the toilet, trailing the fingertips of one hand on the floor. Now and then she paused, glanced back at her hand, and then resumed her progress… She trudged along just this busily on two feet and one hand, while the other arm extended backward this way to pull the toy. Viki had an imaginary pulltoy!" And not only that. Viki sometimes acted as if her pulltoy had got stuck on something. She tugged on the invisible string until she imagined that the toy had gotten free. Once, when her invisible toy was "stuck", she waited until her human caregiver pretended to free the toy, before continuing to play with it.
Some of the more charming examples of animal imagination come from the female gorilla Koko, who was trained to use American Sign Language. Koko routinely pretended that her dolls were her companions, frequently tried to nurse them, and often signed to them, sometimes giving them instructions. In one instance, a five-year-old Koko orchestrated an exchange between two toy gorillas, one blue and one pink. First, looking at the pink gorilla, she signed BAD BAD and then KISS towards the blue one. She then instructed the pair of toys to CHASE and TICKLE before smacking the two dolls together. After wrestling with each doll, Koko stopped and signed, GOOD GORILLA. GOOD GOOD.