I have a rare blood type--AB , which only 4 percent of the U.S. has--and secretly, I always thought it made me kind of special, even though I had no basis for that belief. But in Japan, blood type is used to determine one's personality and temperament. Like astrology, the scientific community often dismisses blood type as an indicator of personality, but that doesn't stop its popularity in Japanese women's magazines, where blood type horoscopes are published. In Japanese video games, blood type is commonly a dimension in character creation. In fact, some Japanese might even be shocked if a foreigner didn't know her blood type.