Athletes are a notoriously superstitious lot. For years, Michael Jordan wore the shorts from his national-championship-winning University of North Carolina days under his Chicago Bulls uniform. Serena Williams won’t change her socks at tournaments she’s winning. Other professional athletes carry lucky charms or perform rituals, like bouncing a basketball in elaborate sequences before a free throw or kissing the golf ball before a putt. Jason Giambi (the former Yankee and current Colorado Rockies first baseman) has said that he slips on a pair of “lucky” thong underwear when his batting average falls. The thong’s reputation is so potent that slumping teammates reportedly beg to borrow it.

Despite this fidelity to charms and rituals, however, there has been little scientific proof that such superstitions work. Does believing in luck actually make you a better athlete? Or would Michael Jordan have been just as successful without his undershorts?

A new study published online in the journal Psychological Science provides some intriguing answers and makes a compelling case that each of us should find lucky underwear of our own.

For the study, researchers in the psychology department at the University of Cologne in Germany completed a series of experiments. In the first, they recruited 28 college students to try to make as many putts as possible on a putting green. Before his or her first attempt, each participant was handed a golf ball. Some were told, “Here is your ball; so far it has turned out to be a lucky ball.” The rest were told, more blandly, “This is the ball everyone has used so far.” Each student putted 10 times.

The students using the “lucky” balls sunk significantly more putts than those who didn’t.

Next the researchers had a different group of students complete a dexterity test. The students were given a plastic cube containing 36 balls and a shelf dimpled with 36 holes. They were told to dip and twist the box until the balls rested in the holes. First, though, they were given instruction from a moderator, who told some of the volunteers, “I press the thumbs for you,” a German idiom that means, approximately, “I’m keeping my fingers crossed for you; good luck.” The rest received neutral directions. By a fairly significant margin, the volunteers who had been offered good luck maneuvered the balls into position fastest.

Finally, the researchers tested whether people performed mental tests (of memory and vocabulary) more proficiently when they had a lucky charm with them. As it turned out, they did. They also reported feeling more confident about their ability to perform the tasks when their chosen charm was tucked up beside them than when it was in the next room (ostensibly to be photographed). Perhaps most tellingly, they tended to work harder and persevere longer at the tasks than the charmless group — apparently believing that since luck was with them, they shouldn’t quit too soon.

The conclusion from these combined experiments was fairly obvious. “Activating a good-luck superstition,” the authors wrote, “leads to improved performance by boosting people’s belief in their ability to master a task.” More precisely, they added, “the present findings suggest that it may have been the well-balanced combination of existing talent, hard training and good luck-underwear that made Michael Jordan perform as well as he did.”

But while this study suggests that superstitions can improve performance, the underlying physiological mechanisms remain complex and rather mysterious. Does the confidence inspired by lucky underwear lower nervous-system arousal, for instance, or otherwise reduce physiological stress? A number of scientists are looking into those issues. But for now, what psychologists — and fans — suspect is that superstitions are more common among the best athletes, the most invested and the hardest-working, the very people you might expect not to need luck.

Another telling recent experiment found that superstitions flourish particularly in situations where talent is nearing its limits. In the 2008 work, researchers at Colorado College in Colorado Springs, had a group of students putt. The first round of putts were easy, measuring only three feet to the cup. The second round consisted of nine-foot putts. Each volunteer putted 20 times at each distance. Students could choose their balls for each putt from a basket containing four different colors. During the easy round, the best putters pulled balls out at random; they weren’t interested in the colors. But the less-able students, those who weren’t good at putting, tended to pick the same colored ball after any successful putt. (It had become their “lucky” ball.)

When the testing moved to the longer putts, the better golfers started picking the same-colored ball after successful putts. As their skills were being challenged, they began turning to luck to increase their chances. Meanwhile, the less-talented putters, who generally missed all of the longer putts anyway, no longer seemed to care which ball they used. Luck couldn’t help them now.

The lesson from this and the other experiments is, at its most basic, that being superstitious is a sign not of weakness but probably “of hope,” says Kristi Erdal, a professor of psychology at Colorado College and the senior author of the putting study. You may be turning to an external, intangible force, but you haven’t given up.

Of course, there can be a downside to being superstitious in sports. “If athletes focus their energies on minor superstitious behaviors over training,” Ms. Erdal said in an e-mail message, “or if the superstition is so entrenched that its disruption (someone steals Jordan’s shorts) leads him to play horribly because of the associated anxiety,” then good luck becomes its opposite. For most of us, though, most of the time, being superstitious is not wholly negative, she wrote. A lucky thong could probably help each of us perform at our best.