RESUMO
Stress induction reduces people's ability to modify their instrumental choices following changes in the value of outcomes, but the mechanisms underpinning this effect have not been specified because previous studies have lacked crucial control conditions. To address this, the current study had participants learn two instrumental responses for food and water, respectively, before water was devalued by specific satiety. Choice between these two responses was then measured in extinction, reacquisition and Pavlovian to instrumental transfer (PIT) tests. Concurrently during these tests, a negative emotional appraisal group evaluated aversive images (stress induction), whereas a control group evaluated neutral images, at the same time as choosing between the two instrumental responses. Negative emotional appraisal abolished the impact of water devaluation on instrumental choice in the extinction test, but did not affect instrumental choice in the reacquisition or PIT tests. These findings suggest that negative emotional appraisal selectively impaired participants' ability to retrieve the expected value of outcomes required to make goal-directed instrumental choices in the extinction test, and that this effect was not due to task disengagement, nullification of the devaluation treatment or impaired knowledge of response-outcome relationships.