Paradoxical effects of stress and an executive task on decisions under risk.

In everyday life, decisions are often made under stress and while being occupied with multiple tasks. It has recently been shown that acute stress impairs decision making under risk. Performing a parallel executive task also caused riskier decision making. To investigate the effects of a combination of these two factors on decision making, we conducted a large (N = 126) experimental study with a 2 × 2 design (stress vs. no stress and parallel task vs. no parallel task). Stress was induced using the Trier Social Stress Test (TSST) and controls underwent the placebo TSST. Salivary samples were collected to assess cortisol and alpha amylase concentrations as markers of the two stress response systems. Decision making was measured using the Game of Dice Task (GDT). A 2-back task served as parallel executive task. Our results revealed a significant interaction between stress and the parallel executive task. In line with our earlier findings, acute stress and a parallel executive task individually tended to impair decision making under risk, manifested by more high risky than low risky choices. Interestingly, stressed participants in the parallel-task condition (GDT plus 2-back) showed similar decision-making behavior as nonstressed single-task participants. Regression analyses revealed executive functions to moderate stress effects on decisions under risk. Reasons for these paradoxical findings are discussed with respect to stress-evoked cognitive alterations that may benefit decision making under risk, if an executive task is performed simultaneously.