You do not need to be a genius to look after yourself. Yet, millions of Americans suffer or die every year from diseases and accidents that they can clearly -- and easily -- prevent.
Increasingly, psychologists are asking why they do not.
Traffic accidents do not have genetic roots. No one has a predisposition to AIDS. Smoking-related lung cancer is not hereditary. And more: Women usually need abortions only when their pregnancies are unplanned. People get heart disease by not exercising and eating unhealthy food. They get ulcers by staying over-stressed. All of them terrible situations. Most self-inflicted.
If psychologists can figure out why people act, well, stupidly, this can give public health campaigns a new edge, and make the millions of dollars government spends to change behavior a better investment. The battle against AIDS, drunk-driving and even the regulation of tobacco might change completely.
"Take unsafe sex," said Lawrence Balter, a professor of applied psychology at New York University. "I mean, how stupid can one be? Why do people still do it?"
Why indeed? Why don't people ever learn? Is it perversity? Inherent character flaws? Skewed judgment?
Is it just a part of being American?
"Climbing Mount Everest, unsafe sex, sky-diving, drinking and driving -- they are all risk-taking behavior," said Frank Farley, the former president of the American Psychological Association. "The essence of America is risk-taking."
And the subject is not new: "It's a problem that has bothered people for thousands of years," said Irwin Hyman, professor of psychology at Temple University in Philadelphia.
He thinks the health lessons sink in only when a person learns about a risk so well that the fear is internalized. In other words, you do not just think that contracting AIDS is a possibility with unsafe sex, but you really believe it can actually happen to you.
"People know if they jump off cliffs they are going to die," he said. "So people don't jump off cliffs. They really believe it."
It is a theory of rational human behavior, the assumption underlying public health campaigns: Given the right information, people will protect themselves.
It is an idea that goes a long way, but apparently not far enough.
"A big part of the problem is that humans are not always rational," said James H. Bray, a psychologist at Baylor College of Medicine in Houston. Sometimes "you tend to follow your emotional responses rather than thinking it through."
And sometimes, we help to incapacitate ourselves. Studies have shown strong correlations between drinking and unsafe sex, for example. People who would normally balk at drunken driving might convince themselves that they will be OK behind the wheel after they have had a night on the town.
Others may know what is the right thing to do, but lack the character to do it.
"We often behave in ways that are convenient or comfortable or appealing or compelling despite the potential harm," said Dr. Balter, who has written a book called "Dr. Balter's Guide to Discipline Without Combat."
"Not everybody will take every chance," he said. ". . . The perception of danger varies from time to time and person to person. You might not think that the odds of getting sick from smoking are as great as they might be."
The same goes for drinking, especially because alcohol notoriously impairs judgment.
Psychologists advise people to take such frailties into account -- when they are sober. That is why having a designated driver helps. Or lots of plain old will power.
"It's partially education," Dr. Balter said. "But beyond that there's conditioning a person to withstand a temptation.
"You teach self-control in gradual increments," he said. "You teach people they can sustain discomfort, they can live with deprivation, they can tolerate delay, they will not be undone by anxiety or frustration."
Sometimes bigger problems are at work. Lighting up a cigarette or sleeping around may be signs of a deeper problem, a troubled psyche.
"They are getting something out of their self-destructive behavior," said Dr. Hyman, who is working on a book on the subject. "The sexually promiscuous girl thinks she is in control. She has no self-respect and thinks it's the only way she can get a man."
"The more self-destructive, the more pathologic the behavior."
Some of this behavior may also be attention seeking. Much like a child who wets his bed every night because it is a way to get the time and attention of his parents, adults "self-destruct" to get attention.