In the service of science, 32 volunteers let scientists at Emory University in Atlanta deliver electrical shocks to their bare feet.

As you might expect, all the participants dreaded waiting for the shocks. But nine of the people, later dubbed the "extreme dreaders," hated waiting for the pain so much that they volunteered to suffer higher voltages in return for shorter delays.

Despite appearances, the study, published today in Science magazine, was not about sadism -- or masochism. Instead, it was designed to test a theory proposed nearly 20 years ago by Carnegie Mellon University economist George Loewenstein.

Dr. Loewenstein, a pioneer in the fast-growing field of behavioral economics, suggested that if people are facing a negative experience, like a visit to the dentist, they may want to get it over with as quickly as possible. If they are facing a positive event, like opening a present, they may want to stretch out the pleasurable anticipation.

While his theory may fit common sense, it clashed with classical economic thinking, which predicted that people would seize pleasurable opportunities quickly and put off unpleasant outcomes.

The Emory experiments in Atlanta not only confirmed Dr. Loewenstein's thesis, but showed that some people are especially loath to wait for the slings and arrows of outrageous fortune.

The results may offer lessons on everything from how to get people to stop avoiding important medical tests to how they can invest their money more wisely.

The experiments were conducted by a team led by Dr. Gregory Berns, who did his residency training in psychiatry at Western Psychiatric Institute and Clinic in Pittsburgh.

Essentially, Dr. Berns said, the tests show that "your state of mind while waiting for something can loom larger than the thing you're waiting for."

When the participants were asked whether they wanted to get the same voltage shock sooner or later, almost all of them chose the shorter interval. But only the extreme dreaders were willing to trade a shorter delay for a higher voltage.

Brain scans showed there wasn't much difference between participants in the two groups in how much pain they experienced, Dr. Berns said, but the extreme group's members showed a sharper response in some parts of their brains shortly after they were told a shock was on the way, proving that for them, the waiting was worse than the jolt.

Such feelings of dread can play out in two ways, Dr. Loewenstein said.

If a person dreads making a decision but is forced to make up his mind, he'll often choose to get it over with quickly. But if he can put it off indefinitely, he'll do that instead.

"I think there are a lot of decisions we make that are driven by dread or fear or anxiety," he said. "People will avoid investing in stocks, for instance, because it's too scary." If they could get over that hurdle, "years later when they retire, they're going to be much better off," he said.

The Emory study may also provide clues for how to deal with people who avoid scheduling unpleasant medical tests, Dr. Berns suggested.

It might be good to offer extreme dreaders the chance to take a test such as a mammogram or a cancer screening when it is first discussed in a doctor's office, rather than having them wait for it.

On the flip side, Dr. Loewenstein said, it may pay to get people to wait longer to make decisions about certain kinds of positive rewards.

In a study last year, he and his colleagues found that when people were offered a certain sum in a year and a larger sum in a year and a day, they usually picked the larger sum. But if they were offered the smaller sum today and the larger one tomorrow, they often picked the smaller amount.

Brain scans showed that the difference in the short-term decisions was that the emotional parts of people's brains had kicked in -- their "hunger" for immediate gratification.

"So if someone is offered a hot dog right now or filet mignon in two hours," he said, "they'll often take the hot dog."