PHILADELPHIA—At first glance, Randy Grebcyk appears to be like any other male. An associate underwriter for Mid-Atlantic Colonial Insurance, Grebcyk, 29, works a 40-hour week and lives alone in a one-bedroom apartment. What sets Grebcyk apart from other males, however, is an unusual lack of shyness and a strong desire for self-expression—qualities that surprise those who meet him, and leave scientists scrambling for explanation.

With his lack of shyness and strong desire for self-expression, Philadelphia's Randy Grebcyk is an oddity among males. Among the 29-year-old's unique interests: alcoholic beverages, cars and the local pro sports teams.

Psychologists studying Grebcyk have coined a term, "extroversion," to describe his unusual behavior.

"It's completely baffling," said MIT researcher Edmund Lawler. "As we all know, men are normally very reticent and reluctant to share their opinions or thoughts. I myself would prefer to be hiding under my desk right now. But this Grebcyk fellow breaks the mold. He's quite an anomaly."

As Grebcyk himself put it: "Whoo-hoo! AC/DC rules! Chevy sucks!"

Most males are by nature content with a quiet, contemplative life, spending their days baking, quilting and meditating thoughtfully. Venturing out in public takes no small degree of coaxing and self-resolve. Not so with Grebcyk.

At any given moment and without warning, Grebcyk is capable of such unorthodox actions as: initiating a conversation with a total stranger; telling an off-color joke; and emitting high-pitched whooping noises.

Or, as Grebcyk recently said, "Yeah! Fifth row tickets, baby! Sweet!"

Researchers have isolated five basic elements through which Grebcyk's unusual traits find their expression: pro football, "classic" rock, alcoholic beverages, the opposite sex, and automobiles.

For example, Grebcyk recently won Philadelphia Eagles tickets on a drive-time show on his favorite sports radio station, WDUG, "The Dugout." As a "huge fan" of the Eagles, Grebcyk was ecstatic, and in the days leading up to the game he could not stop talking about how he had won the tickets, as well as how he had gotten to say "WDUG kicks ass" on the air.

At the game, Grebcyk drew stares and gasps of admiration by appearing shirtless, with one side of his body painted green and the other side white.

"What a delightful, not at all annoying young man," said Shirley Post, 51, who sat near Grebcyk at the game.

Not surprisingly, Grebcyk wants to put his unusual traits to gainful use. He would like someday to become a "stand-up comedian," a person who tells jokes to elicit laughter from others. Grebcyk said he was influenced by his hero, Andrew "Dice" Clay, a comedian who exhibited extroversion similar to Grebcyk's before his career decline in the early 1990s.

"You hear what happened when Michael Jackson's wife got pregnant?" Grebcyk quipped. "He was the one who got morning sickness."

Scientists still cannot find a cause for Grebcyk's unique extroversion. But whatever the cause, everyone agrees that his future is bright.

"I predict big things for Randy," said Jennifer Kessler, his supervisor at Mid-Atlantic. "Such unusual exuberance should be well rewarded, and I think it will be."