Decision making under stress: mild hypoxia leads to increased risk-taking

People tend to take more risks under stressful conditions. In the present study, we examined the effect of mild hypoxia, an unconscious and ongoing stressor, on decisions under uncertainty where probabilities are unknown. Participants completed the Balloon Analogue Risk Taking task (BART) in both a normoxic (20.9% oxygen concentration) and a mildly hypoxic (14.1% oxygen concentration) environment. The results indicate that people take more risks in a mildly hypoxic than in a normoxic environment. Despite inducing significant changes in physiological parameters, the oxygen manipulation remained undetected by participants allowing us to rule out a cognitive appraisal account for the effect. Moreover, the stressor was ongoing allowing us to discount possible post-stress reaction explanations. The current findings extend previous ones about the effect of stress on risk-taking and demonstrate that undetected stressors can increase risk-taking in decision making under ambiguity.