Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Sarah F. Brosnan

Second Advisor

David A. Washburn

Third Advisor

Michael J. Beran

Fourth Advisor

Heather Kleider-Offutt


Species vary in the ease with which they can solve apparently similar problems. For instance, problems will be interpreted differently by different species due to differences such as how they process the world or their ecology. The latter is the focus of the ecological approach to cognition, which posits that ecology influences decision-making such that each species performs better on tasks that are naturally relevant to them. In a previous work, my colleagues and I compared the performance of cleaner fish and nonhuman primates, which differ substantially in brain size and ecology, on a dichotomous choice task derived from the cleaner fish ecology. In the task, subjects chose between two different plates, each containing a same food; if they chose the food from plate A, they could then choose the food from plate B as well, whereas if they chose B first, A was no longer available. Fish were better than primates at solving this task, emphasizing the role of ecology in shaping one species’ decision-making. For my dissertation project, I explored possible explanations for the primates’ poor performance in the task. In a first series of studies, I investigated the possibility that species differed in the task because of differences in the capacity to recognize the relevant cues (i.e. the plate design), to solve it. I thus repeated the task with fish and nonhuman primates, using variations designed to be more salient to primates. In a first experiment, the foods were different colors, whereas in a second experiment, they were hidden to avoid the prepotent response. In a second series of studies, I tested monkeys in a computerized paradigm that differed from the plate task by removing interaction with the human experimenter, which may be distracting, and providing a more standardized testing environment. Finally, in a last study, I investigated one possible cognitive limitation to the primates in the plate task, the failure to use backwards induction to solve it. These studies allowed me to investigate the role of ecology in species’ decision-making, a perspective that is often neglected in studies of cognition.