"Basically, it's a situation where there's nothing you can do to control a hurricane. Obviously, it's there, and there's nothing you can do to stop it. However, there are things you can do to control the negative circumstances that it has left you in.
"Some people will say 'I can plan, I can set up a place to go for a while, I can get my stuff out. There are many things I can do that exert control over the circumstances, even though I can't stop the hurricane.'
"Other people will say, 'Oh my God, there's nothing I can do.' Those are two very different reactions to the very same event."
What's important, Maier thinks, is how people view their circumstances. If they think they're in control, the primitive part of the brain backs off, letting more sophisticated parts take command.
But that brings us back to the original question. Why does it shut down in some people, but not in others?
"It's partly genetics, and partly environmental," Maier speculates. Our genes, of course, play a role in all our functions, but it's not the only role. Our environment also is important, and there's reason to believe that events very early in our lives may have helped prepare us to switch gears following a trauma and move on.
"We're gearing up to do animal experiments where we manipulate experiences early in life," Maier says.
"It may be that experiences of this nature early in life are very formative. People who experience a fair level of control, or ability to cope, early in life are going to view events later as if they are controllable."
If we think we can pick up the pieces and get on with our lives, we probably can, his work suggests.
"What matters is whether you view the events as controllable, not whether they are or aren't," Maier says.
His research indicates that if we think there's nothing we can do about our sorry circumstances, the primitive part of the brain is going to keep sending out those neurological impulses that will keep us in a downward spiral.
Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.