Can blood type determine character?

If you’re a recent arrival to Japan, don’t worry if a new friend asks “What’s your blood type?” Your inquisitor is unlikely to be a vampire. Here, blood type is believed to tell a lot about a person in just a letter or two: A, B, O or AB.

Blood type is thought to lend insight into character and compatibility, which is why it often comes up at group nomikai (as a lively discussion over drinks) and, of course, among the romantically minded (as a sort of litmus test).

But the blood type mythology has created more than just talk. Fortunetellers often base a reading on a person’s astrological sign as well as blood group. Every morning on the news, sometime around the weather report, the day is graded according to luck for each blood type. One Saitama housing company, Saisan Misawa Homes Co. Ltd., requires sales staff to wear badges indicating their name, hometown, hobbies and blood type to put customers at ease. Some kindergartens group children according to blood type and educate them “accordingly,” while some companies base work assignments on blood stereotypes.

Although this way of thinking appears to be deeply rooted in Japanese popular consciousness, historically it is relatively new.

It wasn’t until 1901 that U. S. scientist Karl Landsteiner (1868-1943) identified the various groups of human blood. In 1916, a Japanese doctor, Kimata Hara, published a research paper purporting to link blood group with temperament. Then, around 1925, Japan’s army and navy began typing soldiers’ blood, believing the information would be useful in identifying their strengths and weaknesses. However, no conclusive evidence of a connection between blood type and character resulted from all this research.

Still, the idea persisted. Most influential among those positing a link between blood and character was Takeji Furukawa, who in 1927 published a series of articles titled “The Study of Temperament Through Blood Type.”

Based on studies from ancient Greece to Carl Jung, Furukawa assigned character traits to each blood group as follows:

Type O — calm, patient, in control of their emotions, strong-willed, unyielding and full of self-confidence despite a quiet appearance.

Type A — reserved, mild-mannered, full of worry, indecisive, cautious, deeply moved by things, uncombative and self-sacrificing.

Type B — cheerful, independent, light-hearted, talkative, sensitive, sociable, caring and flamboyant.

Type AB — Group B on the outside, but group A on the inside.

It wasn’t too long before these stereotypes became ingrained in the nation’s mind-set. As early as 1937, a part-time doctor at the Ministry of Foreign Affairs suggested that a group-O person would make a better diplomat.

In the 1970s, Masahiko Nomi expanded on Furukawa’s ideas, describing group Os as extroverted, strong and expressive; group As as introverted, restrained and perfectionist; group Bs as free-thinking, independent and lacking ambition; and group ABs as sensitive, distant and passive. Thanks to growing media coverage, the idea that blood groups were linked to personality became widespread.

Today, people tend to fit others into blood group stereotypes, and comments such as “You are precise and passive, so you must belong to blood group A” now pop up in everyday conversation. Career and partner choices may also be influenced by blood. For example, group A people (gentle) are said to make good teachers and group Os (strong-willed) good army instructors.

Unsurprisingly, however, science does not support any of these beliefs. An individual’s personality is formed by a complex mixture of genetic and environmental influences, and while blood group is genetically determined, any influence on personality must necessarily be very small, if it exists at all. Someone with group A blood may share character traits with another group A person, but certainly not because they share blood groups.

Masao Ohmura, a professor of personality psychology at Nihon University, tries to explain why these ideas became so popular in Japan and why they persist.

He suggests that because the Japanese are genetically quite a homogeneous people, grouping by blood was a way of achieving diversity — if only the illusion of diversity. The population breaks down as 39.1 percent A, 29.4 percent O, 21.5 percent B and 10 percent AB. Ohmura also notes that it was believed that the four blood groups corresponded to the classes of feudal Japan: type O (confident and strong-willed) for warriors; type A (mild-mannered and submissive) for farmers; type AB (intelligent and sensitive) for artisans; and type B (cheerful and outgoing) for tradesmen.

As for why people believe in the system despite the lack of scientific evidence, Ohmura attributes it to what he calls the “FBI effect”: Though traits are Free-size, once Branded, they become Imprinted in our minds. Reinforcement leads to acceptance.

“It is said that mild-manneredness is a distinguishing trait of people with group A blood, but some people with group B, O or AB blood may also share this trait,” Ohmura explained. “When you take a group of general characteristics and put a label such as group O or B to them, it really seems like people labeled group O or B share strong similarities.

“This fact is then imprinted into people’s minds, and they believe in the connection between blood groups and personality.”

Ohmura seems to be saying, as politely as possible, that there are counter-intelligence forces at work.

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