Abstract:

In high-risk and even routine factory work, operators will inevitably encounter stressful events such as time pressure, high workload or emergencies. Numerous psychological and post-accident analyses showed that decision-making error under stress is one of the most common causes of industrial accidents. Previous studies have found that individual factors play an essential role in how we feel and react to stress, moderating stress response and then affecting subsequent decision-making. However, as one of these factors which is closely associated with stress and decision-making, ease of excitation has rarely been explored. Therefore, we conducted the present study to investigate the influencing mechanism of stress on risky decision-making and the moderating effect of ease of excitation. We supposed that stress level (indexed by salivary cortisol and heart rate) was positively correlated with risk-taking behavior, and ease of excitation played a moderating role in this relationship.

Forty-three male participants were recruited for the study. We adopted the Trier Social Stress Test (TSST) to induce acute psychological stress and collected participants’ salivary cortisol, heart rate and subjective emotional states during the experiment to evaluate their stress responses. The Balloon Analogue Risk Task (BART) was applied to measure their risk-taking behavior under stress. The mean adjusted number of pumps across trials was taken as the primary behavioral index. We used the Highly Sensitive Person Scale (SPS) to evaluate ease of excitation before the stress task.

As shown in Figure 1, salivary cortisol, heart rate and negative mood all increased significantly from baseline after the stress task and gradually returned to baseline, which confirmed that the stress manipulation was efficient. Correlation analysis showed that cortisol response positively correlated with the mean adjusted number of pumps at a marginal significance level (r = 0.31, p = 0.06, 95% CI: [-0.06, 0.56]), while heart rate was unrelated to it (see Table 1). Furthermore, hierarchical multiple regression found that ease of excitation moderated the relationship between the salivary cortisol level and the mean adjusted number of pumps (B = 0.04, β = 0.39, p = 0.03, 95% CI: [0.01, 0.07]) (Table 2). To interpret the significant moderating effects of ease of excitation, we conducted a simple slope test. Figure 2 clearly shows that when ease of excitation was one standard deviation below the mean value, the salivary cortisol level could not significantly predict the mean adjusted number of pumps (β = -0.18, p = 0.49, 95% CI: [-0.50, 0.24]). However, when ease of excitation was one standard deviation above the mean value, the salivary cortisol level positively predicts the number of pumping times (β = 0.86, p = 0.01, 95% CI: [0.20, 1.03]). The more salivary cortisol increased, the more pumps did participants decide. However, ease of excitation did not moderate the relationship between the heart rate and the mean adjusted number of pumps (B = 0.06, β = 1.06, p = 0.68, 95% CI: [-0.23, 0.35]).

Altogether, the present study demonstrates that the increased cortisol level under stress positively associates with risk-taking behavior, and ease of excitation moderates the relationship. For individuals with a high level of ease of excitation, the more cortisol they increase, the riskier they are. It may owe to their hyper-sensitivity to internal and external stimuli. The high ease of excitation could be easier to be aroused by the surge of cortisol level and mistake it as the somatic marker to guide decision-making. It highlights the importance of individual differences in understanding stress-related decision-making error and their underlying mechanisms, which further provides scientific implications for selecting and training operators in high-pressure positions.

Key words: acute stress, risk taking, ease of excitation, cortisol, heart rate