Smithsonian National Zoological Park l Friends of the National Zoo



Chikako King

An ability to judge your own knowledge and memory is very useful because you can adjust your behavior appropriately to be successful with a variety of tasks. Think about how you would prepare for a test. If you feel you remember the material, you would relax and take breaks from your studies. But if you think you won’t know the answers, you study more. By adjusting your behavior according to what you know about your own memory, you can be successful in the test.

Although humans use this skill all the time, scientists know little about whether nonhuman primates know what they know and remember when they engage in tasks, such as searching for food. Through my study, I am examining primates’ understanding of their own cognitive activities—and behaviors that depend upon this awareness.

By giving a series of object-choice tasks to the Zoo’s orangutans and gorillas, I am investigating how they behave based upon their understanding of their own knowledge and memory. For instance, the subject is first shown two adjacent blue cups with a favorite food hidden inside one cup. Sometimes, the ape sees the food being hidden; sometimes he does not. The cups are then separated. In some tests, the locations of the cups are switched before the cups are separated. After a short wait, the ape is shown less favored food in a yellow container, which is placed between the two cups. The subject is asked to select a blue cup or the yellow container. If he selects a cup, he is rewarded by picking the cup with food or receives no reward by picking the empty cup. If he selects the yellow container instead, he is rewarded with its contents. It is expected that the apes are more likely to make this “safe choice” when they forget or do not know the location of the favored food.

I am further investigating the apes’ memory awareness by presenting them with a computerized test called “delayed-matching-to-task.” In this task, a sample picture appears on the computerscreen and then disappears once the subject touches it several times. After a short delay, the sample picture reappears with three other pictures and the ape is rewarded by preferable food only if he correctly chooses the sample. In some trials, the ape is asked if he would like to take this memory test or not. In these trials, after the sample picture disappears, two icons appear on the screen: one of them works as the take-test option and other one functions as the escape choice. The former results in the proceeding of the memory test, whereas the latter leads to the ape’s receiving less preferable food.

We predict that the apes should avoid the test when they forget the correct answer, and thus they should perform better in the memory test when they have the option of escaping it as compared to when they are forced to take it.

This research will shed light on nonhuman great apes’ ability to judge their own cognitive activities, which is ultimately related to self-awareness and even consciousness.