Written by: Dr. Blake Morton
Some of you may have seen or heard about our capuchin and squirrel monkeys participating in a special type of problem-solving task, which we’ve affectionately dubbed “the cup game”. This task is designed to measure object permanence, which is a fancy term psychologists’ use to describe why an individual knows that when an object or person goes out of sight, that object/person still exists (i.e. it hasn’t fallen off the face of the earth!). In humans, this mental ability has fully developed by around two years of age, which is why children younger than this typically find the “peek-a-boo!” game hilarious: when you cover your face with your hands, children who have not yet developed object permanence think you’ve disappeared, which is why they act surprised as you “magically” reappear and say “peek-a-boo!” with a grin. It’s a classic stage in child cognitive development.
We’ve known for quite some time that monkeys and other animals like dogs and birds have this ability too. Not surprisingly, this ability should exist in many different kinds of animals where, for example, individuals foraging in trees might benefit from understanding that hidden food items are behind branches and leaves, or that predators concealed by tall grass are still lurking nearby!
We use the cup game at Living Links to train new researchers who come to work with our monkeys. The task is fun and easy to administer, and it gives the monkeys and new researchers an opportunity to get to know one another! Have a look at one of our squirrel and capuchin monkeys participating in the cup game below.
As you can see in the videos, monkeys must choose between two different cups. One cup has a hidden food reward underneath it, the other cup does not. Each monkey gets the chance to play the game twice a day, once in the morning and then again in the afternoon. Within each of these sessions, monkeys can get up to ten food rewards if they choose the correct cup every time. The monkeys’ behaviour suggests that they possess object permanence because they always reach for the cup containing the hidden food reward, even when the position of each cup has been switched. A simple task, but it is clear that object permanence exists in these species – just like us!