Forgetting curve in spider monkeys (Ateles geoffroyi): Effects of delay but not the amount of information.

The forgetting curve is a phenomenon in which animals fail to retrieve information about an event as time passes. We tested this effect in spider monkeys (Ateles geoffroyi) in a task where they had to retrieve a reward hidden in a container after a delay. We combined different delays (0, 5, 10, 20, and 30 s) and different numbers of containers in which the reward could be hidden (2-6) and tested their effects on the accuracy in retrieving the reward. Our data suggest that the longer the delay, the more errors the spider monkeys made. However, a greater number of containers meant only marginally lower accuracy. An analysis of the errors showed that the spider monkeys used spatial information and showed a generalization of responses that depended on the delay; the longer the delay, the greater the generalization and the dispersion of errors. In a second experiment, we tested whether spider monkeys could use visual cues to increase their accuracy. We used the same task with an apparatus with 6 containers and 30 s of delay. Three colors were used as cues, with each color associated with 1 pair of containers. The data showed that the colors did not increase the accuracy of responses but reduced the generalization of the errors. The findings resembled previous findings supporting dynamic field theory, but more investigation is necessary to understand the brain areas and the neural dynamics of spider monkeys to explain and predict their behavior. (PsycInfo Database Record (c) 2021 APA, all rights reserved).