Levels of testosterone in women partly determine how much they trust men, according to a Dutch study published in the U.S. The results support skepticism as an important adaptive trait. "In many mammals, testosterone’s effect on social behavior is mostly to promote aggression when individuals compete for social status or resources. The Dutch team see the hormone’s role in people in a more benevolent light," says the New York Times. “'In humans, however, the hormone seems to motivate for rational decision-making, social scrutiny and cleverness, the apparent tools for success in a modern society,'” the researchers write.