Women are far more likely to follow orders to evacuate, especially women with children. At the same time, women were much more likely to die during the South Asian tsunami. In some villages it was 3 to 1. And that was party because of the average strength it takes to hold onto something. Also it was cultural; women were less likely to know how to swim, as were children. So much of this is based on how we develop our own survival skills before something goes wrong: Even if nothing goes wrong, it might be good to know how to swim.

We gauge risk literally hundreds of times per day, usually well and often subconsciously. We start assessing risk before the disaster even happens. We are doing is right now. We decide where to live and what kind of insurance to buy, just like we process all kinds of everyday risks: we wear bike helmets, or not. We buckle our seatbelts, smoke cigarettes, and let our kids stay out until midnight. Or not.

People will help each other because there is a sense of camaraderie that springs up, which is a survival tactic. You help them because you know you might need their help later. And that is incredibly reassuring.

A lot of the time you see a warning, in the subway, or in a movie theater, the main thrust of the warning will be to not panic if there is an emergency. To listen to directions. Now that's a waste. They could have given you information, but you can see their expectation that you're going to screw up.

Women in particular seem to say things like, "I'm sure I'd be the one screaming and not moving in an emergency." I don't think that's the case. People who've been through really horrible life-or-death situations say that nobody behaves the way they would have expected. But that said, there are predictors.

The one thread that was most surprising and most consistent was the lack of fear that people felt at the worst moment. They felt a lot of fear in early stages, when they're just realizing what's happening. But then things really seemed to be at their peak of terror, the fear went away. You can imagine why that's useful. At that moment your brain needs to focus all its attention on surviving, so people will feel a sense of calm as their brain tries to sort out a plan.

My anxiety about disasters is lower. The more you know, the less scary any of this stuff is. And that's my hope for the book. I want to get people's attention and tell them very valuable and ultimately hopeful information, and you find out nothing is as scary as your imagination.