" 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. Levels of the stress hormone cortisol appear to be a major factor, according to Ruud van den Bos, a neurobiologist at Radboud University in the Netherlands. He and his colleagues have found that the tendency to take more risks when under pressure is stronger in men who experience a larger spike in cortisol. But in women he found that a slight increase in cortisol seemed actually to improve decision-making performance."