Capuchins (Sapajus apella) and squirrel monkeys (Saimiri sciureus) fail to attend to the functional spatial relationship between a tool and a reward

Capuchins (Sapajus apella) and squirrel monkeys (Saimiri sciureus) participated in 3 experiments in which they were presented with 2 objects, one appropriately oriented and the other inappropriately oriented to retrieve a food reward by pulling, replicating prior experiments with nonhuman primates described as evaluating "tool choice." Choice patterns were analyzed to assess whether monkeys learned that tools needed to be oriented with part of the tool on the far side of the reward to pull in the food. Both species learned to choose appropriately oriented tools after a similar number of sessions with a cane-shaped tool in the first task. Both species also transferred to a new tool shape in the second task, but squirrel monkeys' performance on particular trials suggested they did not use the functional relationship between the tool and the food to guide their choices. Tool shapes and configurations in the final task were designed to control for the potential use of extraneous spatial cues. Neither capuchins nor squirrel monkeys chose appropriately oriented tools above chance in control trials. Results suggest both species relied on other spatial cues to perform in previous tasks rather than learning to attend to the functional spatial relationship between a tool and a reward. Species differences emerged in the second task only, as capuchins mastered performance with the new tool shape faster than squirrel monkeys and seemed to use a more complex set of rules to guide their choices. (PsycINFO Database Record (c) 2019 APA, all rights reserved).