It turns out that testosterone might be responsible for more than masculinity and Hollywood action movies: A new study suggests that women who get doses of the hormone are less trusting of strangers, a possible sign that testosterone boosts levels of caution.
The research doesn't prove a direct connection between testosterone, which is found in both sexes. But it does appear to indicate that the hormone helps reduce trust in women and, "in our opinion, protects them from harm," said study co-author Jack van Honk, a psychologist at Utrecht University in the Netherlands.
The overall role of testosterone in the body remains something of a mystery. "We don't know a lot, to be completely honest," said Paola Sapienza, a professor of finance at Northwestern University who studies testosterone and how it affects decision-making. The hormone seems to be connected to aggression, she said, but "nobody really knows the mechanism by which testosterone changes behaviour."
To make matters more complicated in the world of science, it's less clear what it does to women, she said, and there have been relatively few studies into testosterone's effects on them.
How the study was done
In the new study, 24 women, with an average age of 20, were given a dose of testosterone or a placebo under the tongue. Then they ranked the photographs of strangers, using a trustworthiness scale from -100 to +100.
Three days later, the women were given another dose -- testosterone if they'd gotten a placebo earlier, and vice versa -- and then looked at photographs again.
After they'd been given testosterone, the women were less likely to rank faces as being trustworthy, the researchers found. This effect was especially strong in women who were the most trusting to begin with.
Figuring out what this means is the tricky part. "We need to understand what is happening in the brain to draw further conclusions," van Honk said, although he added that the findings appear to show that testosterone makes women more cautious about strangers.
"History tells us, and we tell our children, that giving trust to strangers is naive and dangerous," van Honk said.
If testosterone does make women more cautious about people they don't know, the finding could be important in helping scientists better understand how trust works -- how the brain creates it, adjusts it and makes it disappear.
"Trust is a fundamental ingredient in every human interaction," Sapienza said. "If you remove it, you don't have economic transactions or love or any relationship."
For van Honk, the next step in the research is a brain scan study that aims to figure out what happens in the body when testosterone lowers the levels of trust in people. The current findings were published online in the Proceedings of the National Academy of Sciences. - (HealthDay News, May 2010)