How to Understand the Japanese Blood Type Theory of Personality

Japan has a seemingly infinite number of beliefs which regularly confound unwitting foreigners. One little-known example is the widespread Japanese belief that blood types help determine personality. Knowing a person's blood type is akin to knowing their astronomical sign, and is considered valuable, often public information for many people in Japan.

Difficulty: Moderately Easy

Instructions

1. Understand the history behind the theory. The theory was first published in 1927 as "The Study of Temperament Through Blood Type," by Takeji Furukawa, and was soon offered as an explanation for why Taiwan rebelled during Japan's occupation (many Taiwanese had "rebellious" O-type blood). The theory was popularly revived in the 1970s by Masahiko Nomi, a lawyer and broadcaster with no medical training.

2. Familiarize yourself with the archetypes: Type As are peaceful but high-strung, Type Bs are caring but selfish, Type ABs are rational but indecisive, and Type Os are sociable and honest but dislike authority. Rh has no role in the Japanese theory.

3. Read through any Japanese women's magazines. They often use blood type to measure relationship compatibility. Celebrities, meanwhile, often publicly list their blood type, and even profiles of video game characters mention whether they are Type A, B, AB or O.

4. Watch the Korean film "My Boyfriend is Type B," a romantic comedy whose plot involves a Type A girl dating a Type B man. The girl is actively advised against dating across blood types.

5. Buy a condom from one of the thousands of Japanese vending machines. These condoms are often, somehow, matched to the user's blood type.