Stress and Memory

Instrumental learning is regulated by two memory systems: a relatively rigid but efficient habit system and a flexible but resource-demanding goal-directed system. Previous work has demonstrated that exposure to acute stress, under specific conditions, may shift the balance between these systems towards the habitual system. In the current study, we used a two-day outcome devaluation paradigm with a 75% reward contingency rate and altered food reward categories to replicate and extend our previous findings. Participants learned neutral stimulus-response-reward associations on the first day. On the second day, rewards were devalued by eating to satiety. Subsequently, acute stress was induced in half of the participants using the Maastricht Acute Stress Test, while the other half engaged in a non-stressful control task. Finally, relative goal-directed versus habitual behavior was evaluated in a slips-of-action phase. Results showed that participants successfully acquired the stimulus-response-reward associations, that devaluation was effective, and that stressed participants displayed significant increases in cortisol and blood pressure. Stress led participants to commit more slips-of-action compared with non-stressed controls. The current study extends previous work in showing that the employed instrumental learning paradigm and outcome devaluation procedure are boundary conditions to the stress-induced shift in instrumental responding.