Date of Thesis

Spring 2019

Thesis Type

Masters Thesis

Degree Type

Master of Science


Animal Behavior

First Advisor

Peter Judge

Second Advisor

Regina Gazes

Third Advisor

Elizabeth Capaldi


self-control, delay of gratification, behavioral inhibition, squirrel monkeys, accumulation, exchange


Self-control has been studied extensively in both humans and nonhumans in relation to planning, goal-oriented behavior, and overall higher cognitive function. These investigations have resulted in a vast literature pool afflicted by differing definitions, procedural inconsistencies, and numerous paradigms that were thought to measure self-control. I utilized a within subject design to address the question of what these existing tasks were studying and if they produced similar results. The present study tested squirrel monkeys on four tasks. Two of which were widely accepted self-control paradigms (food exchange and accumulation) that involved refraining from choosing a low-value reward in favor of a high-value reward. Importantly, these two rewards differed qualitatively or quantitatively depending on the task/phase. The other two tasks were highly contested self-control paradigms (cylinder and A-not-B) that involved the inhibition of a prepotent motor response. All squirrel monkeys tested were capable of displaying self-control on all tasks. However, the results indicate that not all self-control paradigms measure the same aspect of self-control, as individual performances varied across the tasks. Task type and previous experience with other self-control tasks did not predict the variability in performance, but the qualitative or quantitative nature of the rewards did. This suggests that researchers should not compare the results from one task to that of another, especially if the nature of the reward differs. Overall, the squirrel monkeys performed quite well on all tasks, indicating that they were promising subjects for future studies of self-control.


A-not-B test demonstration.MOV (38603 kB)
.MOV / video file / 00:00:20 / 4941312 bytes