Capuchin Monkeys (Cebus [Sapajus] apella) Show Planning in a Manual Maze Task

The capacity for planning in nonhuman species has long been an interest of many comparative and cognitive psychologists. There is now considerable evidence that at least great apes show both motor planning and planning for future needs in various contexts and modalities. Few studies, however, have investigated planning ability in a monkey species, and most of these exceptions have used computerized procedures. To gain a broader view, in the current study, we tested capuchin monkeys' capacity for motor planning using the "paddle-box" apparatus, a manual maze task originally designed for testing planning skills in apes (Tecwyn, Thorpe, & Chappell, 2013). This consisted of a box containing different levels of paddles that subjects rotated to drop food into a tube that delivered it to the subject. To evaluate subjects' degree of skill in the task, the initial locations of the food and the final goal (i.e., the "paths" the food could take) were chosen according to the probability of retrieving the reward, starting with those that gave the highest probability of success and moving sequentially to those with the lowest probability. Most subjects solved all levels of difficulty in the task, and capuchin monkeys succeeded as a group in a generalization test with novel paths. These findings demonstrate that some monkeys, like apes, show planning in different contexts and modalities.