For a long while, I thought that the standard blood groupings ( A, B, AB, and O) only had to do with microscopic antigens on my cells. Boy was I wrong. As it turns out, your blood type determines everything about you core personality...or at least that is what many people in Japan seem to believe.

Personally, I think the whole idea of blood types as a basis for determining your personality is as silly as it comes, but it seems that most of Japan disagrees with me. If you live in Japan long enough, it is only a matter of time before someone asks for your ketsueki-gata (血液型), or blood type in order to determine your preordained personality type.

The linking of blood type to personality--known officially ketsueki-gata seikaku bunrui (血液型性格分類)--as is by no means a recent phenomenon. However, the rise of the Internet, TV, and mass communication has perpetuated the myth that your red blood cells magically alter your physiological state. Also, variety TV shows and girl magazines that actively promote uranai (占い), or fortune telling, have been a major force in the propagation of the blood type obsession.

The connection between blood and personality is by no means unique to Japan. Pre-Industrial Revolution European medicine was crazy about the idea of "humors" as represented in bodily fluids, and let's not forget about the practice of "blood letting," formerly used to cure... just about everything. However, what is unique about Japan is how far this superstition has continued into the present day and age.

The man to thank for that is a gentleman named Yoshikawa Takeji (see left). A high school teacher and amateur physiologist by trade, Yoshikawa published a series of works in the 1920s and 1930s expounding on the link between blood and personality. While he was not necessarily the first person to articulate these theories in Japan, he certainly was the most popular.

Despite having been refuted by the Japan Medical Association as early as 1933, the blood-personality link continued to gain traction throughout the 20th century. Apparently, the theory is also popular in other Asian countries like Korea and Taiwan, but I can only vouch for my own experiences here in Japan.

What do Blood Types Mean
Since you probably will be asked about it at least once, it doesn't hurt to know what each type represents, even if like me you think the whole idea is poppycock.

Officially there are two personality facets for each person, the omote (面) and the ura (裏). The former is your outwards traits like outgoingness, ability to interact with others, and so on. The latter is your inner feeling and thoughts that you keep hidden. Ura traits are almost always of the negative variety. Let's take a look....

Omote traits by blood type
  • Type A - These blood types are thoughtful, nice to others, studious, and not afraid to be gutsy. They also have an appreciation for beauty.
  • Type B- People possessing these blood types are known to be optimistic and easy going, but always work at their own pace. They get over lost loves and tragedy quickly. They open up quickly to others and have a flexible, multifaceted personality.
  • Type AB- The owners of this rare blood type are high-minded idealists with little interest in cheap and shallow things. They value privacy and keep public and private affairs separate. They are sensitive and take a simple approach to love.
  • Type 0- These blood types are found in down-to-earth people with straightforward, realistic ways of thinking. They are good with money and strong when faced with adversity. They get along well with others and can fall deeply in love. 
Ura traits by blood type
  • Type A- These individuals are good at putting on a good face even though they are secretly complaining to themselves. They also tend to be judgmental of others to a fault while at the same time fearful of rejection. They are more prone to hysterics and don't work well in hierarchical organizations.
  • Type B- These folks have a tendency to be just too darn nice and often find themselves being used by others. They are also prone to laziness and careless mistakes. They are known for being unrefined and prone to addictive habits like gambling.
  • Type AB- These types tend to be fickle and give up more easily than their peers. They tend to be more selfish and are indecisive, often dragging out decision making processes. AB types are known to be skilled liars and unabashed cynics.
  • Type 0- Those possessing this blood type are known to be overly simplistic with a desire to be the center of any event or space. They tend to be conservative and do not handle tense situations well. Like Type A individuals, they don't work well in hierarchical organizations.
Do these traits sound suspiciously like overly vague generalities? Well, that is probably because they (in this author's opinion) are. However, the above traits are just one interpretation among many. There are literally whole books written about blood types and personality traits as well as how different types interact socially and intimately.

However, despite my cynicism, some fellow skeptics have pointed out that talking about your blood type can be a good ice breaker or conversation starter. Even if you don't believe in it, chatting about your blood type can be a good social tool.

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