To Brake or Accelerate When the Light Turns Yellow?

Abstract

This article reports on a study undertaken to examine age differences in the effects of stress on risky decisions, such as deciding whether to brake or accelerate as one drives up to a traffic light that has turned yellow (amber). The authors had younger adults (aged 18-33 years; N=45; 22 males) and older adults (aged 65-89 years; N=40; 21 males) play a computer-based driving game either after a stress challenge or in a control condition. The study included 15 driving game trials in which drivers accumulated points by getting their simulated vehicle stopped before the traffic light turned red. Participants randomly assigned to the stress condition submerged their non-dominant hand in ice water (2.0 to 4.2 C) for three minutes. In the control condition, participants held their hand in warm water (37.3 C to 38.8 C) for three minutes. They started the driving game 18 min after the stress challenge, during the period of peak cortisol response to acute stress. Compared with the control group, the stress group’s salivary cortisol levels increased by the time of the game for both younger and older adults, with no significant age difference in the increase. The stress condition also resulted in higher post-experiment self-ratings of stress during the water task for both younger and older adults. Being stressed reduced older adults' final scores by nearly half, but did not significantly affect younger adults' scores. Stressed older adults risked driving for a smaller proportion of the yellow light. Stress also increased older adults’ stopping rate, but did not significantly affect younger adults’ stopping rate. Overall, older adults had fewer losing trials (M = 27%) than younger adults (M = 41%), but there were no effects of stress on losing rates. Consistent effects of stress were found on driving time, stopping rate and points throughout the game. The authors conclude that their results reveal that stress can change older adults’ decision strategies. After a stress challenge, older adults not only risked significantly less driving time but also stopped and restarted more frequently than those in the control condition. The age differences in the effects of stress were robust, occurring even when each sub-phase of the game was analyzed separately and when male and female data were analyzed separately. They call for addition research using different measures of risky decision making to see if these age differences are specific to risky decisions made under time pressure (as in the current task) or also extend to other decision tasks.