Smelling fear? Study provides evidence that chemosensory anxiety signals reduce trust and risk-taking in women

The odor of anxiety-induced body sweat can make women become more risk adverse and less trusting of others, according to new research published in the journal Biological Psychology. The new findings indicate that chemosensory anxiety signals can act contagiously but predominantly affect women.

Animals commonly use their sense of smell to detect predators and other threats in their environment. Recent findings have also provided evidence that stress can be communicated between individuals via chemosensory cues.

“Most intriguing for me is that people communicate their motivational and emotional state via sweat derived chemosignals, but without being conscious about this process. Meanwhile, we know a lot about the brains’ response to these chemosignals but much less about effects on overt behavior. That’s why this study was very important to me,” said study author Bettina M. Pause, a psychology professor at Heinrich-Heine-University Düsseldorf.

Smelling fear? Study provides evidence that chemosensory anxiety signals reduce trust and risk-taking in women

The researchers conducted a series of five studies with 159 non-smoking women and 55 non-smoking men to examine whether chemosensory anxiety signals reduced trust and risk behavior.

An experimentally-verified task known as The Trust Game was used to measure trustworthiness. In the game, one participant is given a small amount of money and then chooses how much he or she wants to transfer to a fictional co-player (the trustee). Any amount of money that is invested is then tripled. The participants are told that the trustee will subsequently decide how much of this money to give back.

To assess the willingness to take risks, the researchers also used a variant of The Trust Game (known as The Risk Game) in which participants were told the co-player was a computer and the amount of money retransferred back to them after the initial investment would be random.

As they played through multiple trials of either game, the participants were exposed to various odors just before they had to decide how much money to invest. The odors included sweat that was collected from men experiencing anxiety during a Trier Social Stress Test and sweat collected from men during mild exercise. The participants wore a hospital oxygen mask that was hooked up to an olfactometer, allowing the researchers to precisely control the level of odor the participants were exposed to.

The researchers found that women tended to transfer less money after being exposed to chemosensory anxiety signals compared to the other odors. This was true even when the odor from anxiety-induced sweat was not consciously detectable.

“Anxiety states are communicated below the perceptual threshold through chemosensory signals derived from axillary sweat,” Pause told PsyPost. “Like in most other animal species, some emotions are probably transmitted contagiously. Thus, in women, the anxiety of the sender is transmitted to the perceiver via chemosignals. Experiencing anxiety reduces the intention for risky decisions, and therefore also the willingness to trust other individuals in bargaining situations.”

“It seems that men are less reactive to chemosensory anxiety signals,” Pause noted. However, men do not appear to be totally unresponsive. Previous research has found that the smell of putrescine, a chemical produced by decaying tissue of dead bodies, initiates threat management responses among both women and men.

Another study found that exposure to stress-induced chemosignals activated brain regions responsible for emotional processing, regardless of sex. “Here, fight-flight behavior seems to be activated through the chemosignals,” Pause said.

The study, “It’s trust or risk? Chemosensory anxiety signals affect bargaining in women“, was authored by Lukas Meister and Bettina M. Pause.