Dr. Mather and her team taught people a simple computer gambling game, in which they got points for inflating digital balloons. The more they inflated each balloon, the greater its value, and the risk of popping it. When they were relaxed, men and women took similar risks and averaged a similar number of pumps. But after experiencing the cold water, the stressed women stopped sooner, cashing out their winnings and going with the more guaranteed win. Stressed men did just the opposite. They kept pumping — in one study averaging about 50 percent more pumps than the women — and risking more. In this experiment, the men’s risk-taking earned them more points. But that wasn’t always the case.

In another experiment, researchers asked participants to draw cards from multiple decks, some of which were safe, providing frequent small rewards, and others risky, with infrequent but bigger rewards. They found that the most stressed men drew 21 percent more cards from the risky decks than from the safe ones, compared to the most stressed women, losing more over all.

Across a variety of gambles, the findings were the same: Men took more risks when they were stressed. They became more focused on big wins, even when they were costly and less likely.