Date of Award


Document Type


Degree Name

Master of Arts (MA)



First Advisor

Donna J. Toufexis


Decision-making in dynamic environments involves a tradeoff between deliberate and habitual modes of behavior. Optimal decision-making often requires a balance between these two systems, but following stress, organisms tend to shift away from deliberation and towards habitual control. Although this has been demonstrated across a variety of tasks involving multiple memory systems, few studies have examined how acutely stressful events may differentially affect the learning and performance of an instrumental response. It is also unknown how acute stress affects the integration of goal-directed actions and habits in hierarchical planning of instrumental behavior. Here, we examined whether acute stress experienced before acquisition training (Experiment 1), or prior to the test of expression (Experiment 2) would influence goal-directed and habitual control of an instrumental response in female rats using an outcome devaluation paradigm. Experiment 3 assessed the effect of acute stress on the integration of goal-direction and habit by asking whether stress facilitates the execution of habitual sequences of actions in a serial decision task. The results of Experiment 1 indicated that acute stress experienced before acquisition promotes habit learning, while the results of Experiment 2 indicated that habitual control of responding was present when stress was experienced just prior to the test. These data suggest that acute stress may generally facilitate habitual control over instrumental responding in free-operant tasks when response feedback is withheld. In Experiment 3, we found that on a strategic level, rats exhibited goal-directed planning of habitual action sequences under both stressed and non-stressed conditions. However, stress caused distinct effects on the structure of goal-directed planning and the performance of habitual action sequences, decreasing the flexibility and precision with which behavior was executed. These results indicate that for serial decision tasks which incentivize active monitoring of response feedback, the overall structure of decision-making remains intact following stress despite modest degradation in action planning and sequence execution. Collectively, these findings may shed light on the cognitive mechanisms by which stress contributes to impairments in decision-making, as occurs in numerous psychological conditions.



Number of Pages

102 p.

Available for download on Wednesday, May 28, 2025