How Primates Think About Hidden Objects
Emma Collier-Baker
Imagine that your pencil case spills inside your backpack. When you pull out the empty case, you’ll look for the pencils in the backpack. Your ability to think helps you figure out where the pencils are even though you didn’t watch them spill out of the case.
I am a Think Tank scientist at the National Zoo and a post-doctoral research fellow from the School of Psychology, University of Queensland, Australia, and I am working with orangutans, gorillas, and gibbons to determine how they think about objects even when they can’t see them.
I will also study how apes recognize themselves in mirrors and video feedback and if they know when someone is imitating their actions.
How Am I Studying the Zoo's Apes?
- I first train the apes to point to containers that have food inside.
- An ape observes as I hide a piece of food in a small container.
- I move the container to two of four boxes and surreptitiously transfers the food to one of the boxes. Then I show the ape that the container is now empty.
- The ape points to where he thinks the food is. There are three types of choices:
- If the ape chooses the correct box right away, he is rewarded with the treat inside.
- If he chooses one of the boxes that the container did not visit, he is shown the correct location but does not receive the reward.
- If he chooses the box that I only pretended to put the reward into, he is shown that it’s empty and allowed to choose again. Can he mentally track back to the other box visited by the container and infer that the reward must be in there?
What Does Her Study Reveal?
Similar research has already shown that chimpanzees and two-year-old human children can successfully locate objects in this type of task. In contrast, most other animals tested—including various monkey species, dolphins, dogs, and cats—have failed the task at this level of difficulty.
Repeating the study with orangutans, gorillas, and gibbons allows scientists to compare mental skills in several different species. The self-recognition and imitation recognition tests that I am also conducting with the apes here at the Zoo tap into related mental processes. The results promise to add to our overall understanding of primate cognition and the evolution of the human mind.
