We've seen it over and over the past few weeks. After disaster strikes, some people pick up the pieces and move on with their lives. Others find it far more difficult to continue and seem paralyzed by events beyond their control.
Why is it so much more difficult for some people to deal with disasters than it is for others? How is it that the guy down the road can say "OK, the house and all I had is gone, but I'll rebuild," while a neighbor collapses in agony and indecision?
The reason, according to one body of research, lies in the fundamental way the brain functions, and whether we believe we really are in control of our lives.
Steve Maier of the University of Colorado in Boulder is a psychologist who specializes in neuro-chemistry, or the chemistry that regulates activities in the brain. He has been looking at this issue for some time and believes the answer lies in the level of control exercised by a very primitive part of the brain.
"We're looking to see what happens in the brain when bad things happen," Maier says. So far his research, mostly involving laboratory rats, indicates that when bad things happen, a "very primitive" part of the brain is the first to react.
That part of the brain evolved very early in animals, and for good reasons.
"In primitive species, and in simple organisms, when something bad happens the only way that organism can adapt to that event is by altering its physiological reaction," he says. In other words, fight or flee.
"A primitive organism doesn't really have the behavioral capacity to do much about negative events," he says. So a primitive part of the brain orders the system to produce more energy, for example, and to beef up the repair mechanism in case of injury, and, of course, to hit the road.
"The trouble is in primitive organisms these negative events that happen are usually fairly brief in time," Maier says. "You get attacked by the tiger and you either are going to make it or you aren't."
Flash forward and you find a much more sophisticated animal, namely us, and we are in a very different situation.
"Our negative events often are quite prolonged, such as Katrina," Maier says. "So these people are caught in negative circumstances for weeks and months."
But the primitive part of the brain still sets certain physiological processes in motion. That may be initially good (take shelter from the wind, for example) but it's less helpful for the following weeks and months, he says. "It was really designed to handle brief emergencies."
Maier believes that for some people, the primitive part of the brain remains in command, sending signals to other parts of the brain to remain on red alert. That can elevate stress and depress the immune system, leaving the victim more vulnerable and unable to cope with the circumstances.
But for others, the primitive area shuts down, letting more sophisticated parts of the human brain take control.
Why should it work differently for some than for others?
The answer, Maier speculates, may lie at least partly in how we view our ability to deal with unpleasant circumstances.
Citing Katrina as a "perfect example," Maier says this:
"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.