If you are not a person who handles stress well, you are unlikely to enter a high-risk, high-reward field like sales, instead something calmer will be more suitable, even if the pay is much lower. Making less money did not cause your stress level, stress caused you to make less money, according to a new paper by scholars at Ecole Polytechnique Fédérale de Lausanne.

On a biological level, they associated the effects of stress with the release of the hormone cortisol in the Psychoneuroendocrinology paper. 

Confidence is essential to our ability to compete in society, the authors note. When we don't feel confident, we are less likely to make the kind of decisions that can give us a financial and social edge over others. By driving social competition, confidence becomes central in the organization and function of human societies, and marks the way individuals interact with each other. But what really drives confidence?

Two major factors seem to be stress and the person's general anxiety. Such "trait anxiety" describes how prone a person is to see the world as threatening and worrisome. The question, however, is how stress and trait anxiety impact an individual's confidence in a competitive context. 

The teams of Carmen Sandi at EPFL and Lorenz Goette at the University of Lausanne (UNIL) have now shown that stress can actually boost the competing confidence of people with low trait anxiety, but significantly reduce it in people with high trait anxiety. The scientists designed an elegant behavioral experiment, which began with more than two hundred people taking two online tests: one to assess their IQ, and one to measure their trait anxiety. 

A week later, about half of the study's participants underwent a standard psychological procedure (called TSST-G) designed to cause acute social stress, such as going through a mock job interview and performing mental arithmetic tasks before an impassive audience. The other half of the participants formed the control group, and did not undergo the stress-inducing procedure.

All participants, stressed and non-stressed, were then given two options in a game where they could win money: they could either take their chances in a lottery, or they could use their IQ score to compete with that of another, unknown participant's; the one with the higher IQ score would be the winner.

In the non-stressed, control group, nearly 60% of participants chose the IQ score competition over the lottery, showing overall high confidence in the participants, regardless of their trait anxiety scores. But in the group that experienced stress before the money game, things were different. The competitive confidence of participants varied depending on their trait anxiety scores. In people with very low anxiety, stress actually increased their competitive confidence compared to their unstressed counterparts; in highly anxious individuals, it dropped.

The findings suggest that stress is a catalytic force acting on a person's competitive confidence. Stress, it seems, can raise or suppress an individual's confidence depending on their predisposition to anxiety.

Stress and cortisol

The researchers also found that the effects of stress on the participants' confidence were mediated by the hormone cortisol, which is normally released from the adrenal glands, on the top of our kidneys, in response to stress. The team examined saliva samples from the stressed participants for the presence of cortisol. In people with low anxiety, those that showed higher confidence also showed a higher cortisol response to stress. But in highly anxious people, high cortisol levels were associated with lower confidence, which connects the behavioral effects of stress to a biological mechanism.

The findings of this behavioral experiment can be seen as a simulation of confidence in social competition and the way it relates to socioeconomic inequality. Studies have shown that, in areas with wide socioeconomic inequality (e.g. a wide rich-poor gap), people on the low end of the social ladder often experience high levels of stress as a consequence.

"People often interpret self-confidence as competence," says Carmen Sandi. "So if the stress of, say, a job interview, makes a person over-confident, they will be more likely to be hired - even though they might not be more competent than other candidates. This would be the case for people with low anxiety."

Far from being only a product of competitive inequality, stress must now also be regarded as a direct cause of it. In other words, stress can become a major obstacle in overcoming socioeconomic inequality by trapping highly anxious individuals in a self-perpetuating loop of low competitive confidence.

Carmen Sandi is now interested in relating the effect of stress on confidence with brain imaging. Although there is much yet to be learned in this area, she believes that it can change the way we look at social dynamics as a whole. "Stress is an important engine of social evolution," she says. "It affects the individual, and by extension society as whole."

Paper: Goette L, Bendahan S, Thoresen J, Hollis F, Sandi C. Stress pulls us apart: Anxiety leads to differences in competitive confidence under stress. Psychoneuroendocrinology 18 February 2015.