MOVEMENTS in financial markets are correlated to the levels of hormones in the bodies of male traders, according to a study by two researchers from the University of Cambridge (newscientist.com).

John Coates, a research fellow in neuroscience and finance, and Joe Herbert, a professor of neuroscience, sampled the saliva of 17 traders on a stock trading floor in London two times a day for eight days. They matched the men’s levels of testosterone and cortisol with the amounts of money the men lost or won on the markets. Men with elevated levels of testosterone, a hormone associated with aggression, made more money. When the markets were more volatile, the men showed higher levels of cortisol, considered a “stress hormone.”

But, as New Scientist asked, “which is the cause and which is the effect?”

According to the researchers’ analysis, the men who began their workdays with high levels of testosterone did better than those who did not.

“The popular view is that experienced traders can control their emotions,” Mr. Coates told New Scientist. “But, in fact, their endocrine systems are on fire.”