Do orangutans (Pongo pygmaeus) know when they do not remember?
Metacognition refers to the ability to monitor and control one’s own cognitive activities such as memory. Although recent studies have raised an interesting possibility that some species of nonhuman animals might possess such skills, subjects often required a numerous number of training trials to acquire the effective use of metacognitive responses. Here, five orangutans (Pongo pygmaeus) were tested whether they were able to escape spatial memory tests when they did not remember the location of preferred reward in a relatively small number of trials. The apes were presented with two identical cups, under one of which the experimenter hid a preferred reward (e.g., two grapes). The subjects were then presented with a third container, “escape response”, with which they could receive a less preferred but secure reward (e.g., one grape). The orangutans as a group significantly more likely selected the escape response when the baiting of the preferred reward was invisible (as compared to when it was visible) and when the hiding locations of the preferred reward were switched (as compared to when they remained unchanged). Even when the escape response was presented before the final presentation of the memory test, one orangutan successfully avoided the test in which she would likely err. These findings indicate that some orangutans appear to tell when they do not remember correct answers in memory tests.
KeywordsMetacognition Orangutans Escape response
I thank Lisa Stevens for allowing me to work with the great apes at the Smithsonian National Zoological Park and the zookeepers of the Great Ape House for their support. I also thank Milton Tierney for constructing the testing apparatus. This study was supported by a research grant from the David Bohnett Foundation. All of the experiments complied with the current laws of the country in which they were conducted.
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