Testing the limited resource model and its effect on task performance in tufted Capuchin monkeys (Cebus apella)
The limited resource model of self-control was examined in capuchin monkeys in two experiments. Consistent with the model, it was hypothesized that an act of self-control would deplete a cognitive resource, thus impairing performance on a subsequent self-control task. In the first experiment, monkeys were randomly assigned to conditions with self-control exertion (experimental condition) or without self-control exertion (control condition). In the experimental condition, the four subjects were trained to sit on a crate and wait for a protein food reward for 20 seconds for ten trials in a row. The monkeys were then given the choice between opening one unlatched box for one piece of food or searching through a 6-box array of latched boxes for several food rewards in a delay of gratification task. In the control condition, the subjects were given the delay of gratification task without the prior self-control trials. Three of the monkeys exhibited a preference for choosing the 6-box array on days where no prior self-control was exerted, and one monkey showed no difference. Experiment 2 used the same self-control task but changed the second task to an impenetrable box. Five monkeys persisted significantly longer at trying to open the box in the control condition where no prior self-control was used (p < .01). Together, the results from both experiments support the limited resource hypothesis by showing that when self-control is exerted it negatively affects subsequent task performance in Cebus monkeys.