Typecasting, Japanese Style: blood type is widely considered a major influence on personality and ability in Japan. But can it really determine who makes the best politicians, bankers, or baseball, players?

Americans have their astrological signs and horoscope charts, but for many Japanese, clues to people's character and destiny can be found much more simply: in their blood type.

Japanese popular culture has been saturated by blood typology for decades. Dating services use it to heap make matches. Employers use it when evaluating job applicants. Blood-type products--everything from soft drinks to chewing gum--are found all over Japan.

"Japanese tend to have a fairly strong kind of inherent belief that genetics and biology really matter in terms of people's behavior," says Theodore Bestor, a professor of Japanese studies at Harvard University. "So I think Japanese might be much more predisposed to thinking about a kind of genetic basis for personality than most Americans would.

"In everyday life in Japan, blood type is used as a kind of social lubricant, a conversation starter," says Bestor. "It's a piece of information that supposedly gives you some idea of what that person is like as a human being."

So it was no surprise to Japanese baseball fans that the Boston Red Sox just spent more than $52 million for Japanese pitcher Daisuke Matsuzaka. For the Red Sox, Matsuzaka's statistics said it all: a 108-60 record with a 2.95 earned run average in eight seasons with the Seibu Lions, a team about 30 miles west of Tokyo.

But in the eyes of many Japanese, Matsuzaka's most revealing stat is his Type O blood. By Japanese standards, that makes Matsuzaka a warrior, and thus someone quite capable of striking out opposing players like the New York Yankees' Alex Rodriguez or Derek Jeter.

FOUR TYPES

In Japan, people with Type O are commonly thought of as warriors because they are said to be self-confident, outgoing, goal-oriented, and passionate. According to a Japanese journalist who helped popularize blood typology with a best-selling book in 1971, people with Type O make the best bankers, politicians and--Japanese believe--professional baseball players.

A person can have one of four blood types, A, B, AB, or O, and while the most common blood type in Japan is Type A, many prominent Japanese baseball players are like Matsuzaka, Type O.

That group includes Hideki Matsui of the Yankees, Kazuo Matsui of the Colorado Rockies (and formerly of the New York Mets, where he was a huge disappointment) and Tadahito Iguchi of the Chicago White Sox.

WARRIOR OR HUNTER?

But there are exceptions, and in this instance one of them would appear to be Ichiro Suzuki of the Seattle Mariners, who has become one of the great hitters in major-league baseball since joining the Mariners in 2001. Suzuki is Type B.

"That makes sense in a way," says Jennifer Robertson, a professor of anthropology at the University of Michigan who specializes in Japanese culture and history. Robertson added that people with Type B, known as hunters, are said to be highly independent and creative.

And creative would be a good adjective to describe Suzuki at the plate, where he sprays the ball to all fields and sometimes seems to hit to an exact spot. Suzuki set the major-league record for hits in a season with 262 in 2004.

Can any of these correlations be scientifically supported?

The medical community doesn't think so. Even in Japan, they are accepted on faith.

"There's absolutely no evidence that you can predict batting average by blood type or that there are different character traits that you can define by blood type," says Dr. Marc Siegel, a professor at the New York University School of Medicine.

"To me, it lines up with astrology. Some people will say if you're a Gemini, you're more aggressive. I know a surgeon that will only operate on certain phases of the moon. But there's absolutely no scientific evidence."

All this will play out as Matsuzaka faces Hideki Matsui throughout the season. In Boston and New York, the competition will be Red Sox pitcher versus Yankee hitter, right-hander versus left-hander, high-priced Japanese athlete versus high-priced Japanese athlete.

May the best Type O prevail.

David Picker writes about sports for The New York Times.