On this last day of the work week before the 4th of July weekend, I can't passing along this little tidbit. A study published today in the journal Scientific Reports and picked up by Bloomberg Business News concludes that people—and by "people" I mean young men—with more testosterone and cortisol coursing through their veins were likely to make risky decisions about investments. Scientists ran a series of experiments involving make-believe stock market trading floors. After measuring hormone levels through saliva tests and setting the traders loose in groups of men, women or mixed-gender, the study found that young men, in particular, were prone to dodgy decision-making at higher hormone levels. Here's what the scientists concluded: "Cortisol directly affected subjects’ willingness to take risks. Testosterone...was associated with significantly increased optimism regarding price change expectations, making subjects more likely to expect stock prices to increase." In other words, the hormones in our young, male traders might be destabilizing your retirement portfolio. As Oliver Staley from Bloomberg writes, "Want to calm financial markets? Add more women and older people to the young men on trading desks."