Acute stress affects risk taking but not ambiguity aversion

Abstract

Economic decisions are often made in stressful situations (e.g., at the trading floor), but the effects of stress on economic decision making have not been systematically investigated so far. The present study examines how acute stress influences economic decision making under uncertainty (risk and ambiguity) using financially incentivized lotteries. We varied the domain of decision making as well as the expected value of the risky prospect. Importantly, no feedback was provided to investigate risk taking and ambiguity aversion independent from learning processes. In a sample of 75 healthy young participants, 55 of whom underwent a stress induction protocol (Trier Social Stress Test for Groups), we observed more risk seeking for gains. This effect was restricted to a subgroup of participants that showed a robust cortisol response to acute stress (n = 26). Gambling under ambiguity, in contrast to gambling under risk, was not influenced by the cortisol response to stress. These results show that acute psychosocial stress affects economic decision making under risk, independent of learning processes. Our results further point to the importance of cortisol as a mediator of this effect.

Keywords: ambiguity; cortisol; decision making; gain/loss domain; risk; stress; uncertainty.

Figure 1

Behavioral paradigm. (A) Example displays of risk trials. Colors indicate the domains (yellow: gains; green: losses; blue: neutral). Amounts that can be won or lost are depicted above the bars, or in case of the mixed domain, above and below, respectively. Height of the colored part of the bars indicates the probability to win or lose and was varied at three levels (1/3, 1/2, 2/3). (B) Example displays of ambiguity trials. Ambiguity was introduced through gray occluders overshadowing all or part of the probability information. Occluder sizes varied at three levels (complete, 1/2, 1/3; cf. panels from left to right).

Figure 2

Physiologic stress markers. Time course of salivary cortisol (A) and heart rate (B). Gray bars indicate the timing of the Trier Social Stress Test for Groups (TSST-G). Depicted are means ± standard errors of the mean (s.e.m.).

Figure 3

Subjective stress markers. Means ± s.e.m. of the change scores of the mood questionnaire MDBF (Mehrdimensionaler Befindlichkeitsfragebogen) from the measurement before the stress induction to the measurement afterwards. Negative change scores indicate an increase in negative mood (mood scale), an increase in restlessness (calmness scale), and an increase in sleepiness (wakefulness scale). Simple contrasts comparing cortisol responders to nonresponders and controls were used to follow up significant main effects (^**p < 0.01).

Figure 4

Risky choices in the decision task. Percentage (± s.e.m.) of choices of the risky option (vs. sure amounts) in the three domains of the risk part of the decision making task. Simple contrasts comparing cortisol responders to nonresponders and controls were used to follow up significant main effects (^*p < 0.05, ^**p < 0.01).

Figure 5

Ambiguous choices in the decision task. Percentage (±s.e.m.) of choices of the ambiguous option (vs. risky lotteries) in the two domains of the ambiguity part of the decision making task.