Stress changes how people make decisions

It's a bit surprising that stress makes people focus on the way things could go right, says Mara Mather of the University of Southern California, who cowrote the new review paper with Nichole R. Lighthall. "This is sort of not what people would think right off the bat," Mather says. "Stress is usually associated with negative experiences, so you'd think, maybe I'm going to be more focused on the negative outcomes."

But researchers have found that when people are put under stress -- by being told to hold their hand in ice water for a few minutes, for example, or give a speech -- they start paying more attention to positive information and discounting negative information. "Stress seems to help people learn from positive feedback and impairs their learning from negative feedback," Mather says.

This means when people under stress are making a difficult decision, they may pay more attention to the upsides of the alternatives they're considering and less to the downsides. So someone who's deciding whether to take a new job and is feeling stressed by the decision might weigh the increase in salary more heavily than the worse commute.

The increased focus on the positive also helps explain why stress plays a role in addictions, and people under stress have a harder time controlling their urges. "The compulsion to get that reward comes stronger and they're less able to resist it," Mather says. So a person who's under stress might think only about the good feelings they'll get from a drug, while the downsides shrink into the distance.

Stress also increases the differences in how men and women think about risk. When men are under stress, they become even more willing to take risks; when women are stressed, they get more conservative about risk. Mather links this to other research that finds, at difficult times, men are inclined toward fight-or-flight responses, while women try to bond more and improve their relationships.

"We make all sorts of decisions under stress," Mather says. "If your kid has an accident and ends up in the hospital, that's a very stressful situation and decisions need to be made quickly." And, of course, big decisions can be sources of stress all by themselves and just make the situation worse. "It seems likely that how much stress you're experiencing will affect the way you're making the decision."