MEN with above-average levels of testosterone and masculine features, such as prominent jaws and cheekbones, are more likely to make riskier financial investments, researchers at Harvard University say.

The sex hormone may have played a role in the financial crisis that is crippling Wall Street with the scientists suggesting that long-term, above-average testosterone levels lead to irrational risk taking, Anna Dreber, lead author of Program In Evolutionary Dynamics , said.

Previous studies have shown traders make more money on days when their testosterone levels are higher, and male-dominated workplaces such as financial institutions may perpetuate those levels as colleagues egg each other on, Ms Dreber said.

"These findings help us to understand the motivations for risk-taking behaviour, which is a major component of economic theory," Ms Dreber said. "Risk preferences are one of the most important preferences in economics, and yet no one knows why they differ between men and women, why they change over age, or what makes men trade more in the financial market."

The findings are based on saliva samples from 98 male Harvard students taken before they played an investment game with $250 in real cash. Researchers found that a man whose testosterone levels were more than one standard deviation above the mean invested 12 per cent more than the average man into the risky investment.

The students with more masculine facial features invested 6 per cent more than their softer-featured peers.