Culture and Society
PUBLISHED
Off the top of your head, do you know your blood type? If you grew up in the English-speaking world, there's a decent chance you have no idea. But over in Japan, this information can be a vital piece of self-knowledge, used to shape how you perceive yourself and everyone around you.
There’s an old theory that blood types can be inextricably linked to a person's personality and their compatibility with others, especially in affairs of the heart. Many blood-type believers use it in the same way others look at astrology, to ponder love interests and justify the quirks of their personality.
And just like astrology, it's widely regarded as pseudoscience, built on shaky evidence and superstition. But in parts of Japanese culture, where it's known as ketsueki-gata, belief in blood types remains a serious business.
You are what you bleed
It starts in school when young kids are sometimes split up into different groups based on their blood type. This, in theory, is a well-meaning attempt to adapt teaching methods based on the child’s sensibilities and individual needs.
When you enter the job market, some employers might ask for your blood type prior to offering an interview. If you get the job, the workplace may assign employees to different tasks best suited, in their estimation, to their blood type.
These practices have started to be quelled in recent years on the basis of discrimination laws, but they quietly persist in other parts of the culture. Gossipy magazines will run dating columns that often underscore the importance of compatible blood types in one's love life, as do dating apps and face-to-face matchmaking events.
Tarō Asō, who briefly served as the Japanese Prime Minister from 2008 to 2009, proudly revealed to the world that he’s blood type A as a way to bolster the public image he wanted to project to would-be voters.
What the theory says about your blood type
Type A, by the way, is associated with traits like punctuality, patience, sensitivity, loyalty, consideration, and responsibility – all qualities you’d likely want in a leader. At their worst moments, they can be fastidious, fussy, and overly serious – which, again, are not necessarily bad traits in a leader.
Under this belief structure, the traits of a person with Type O might also make for an adept statesperson: rationality, organization, optimism, confidence, resilience, and competitiveness. Like all great dictators, though, they can be guilty of vanity and insecurity.
Meanwhile, a Type AB is more of the arty type: artistic, serious, thoughtful, and caring, albeit indecisive and aloof. Type B is vaguely similar, associated with traits like creativity, passion, individualism, and adventurousness. They can, however, also be a bit irresponsible and erratic.
Blood type is genetic and easy to identify, plus a portion of personality is inherited, so the idea of a biological link isn't absolutely absurd. Nevertheless, there is very little modern, empirical evidence to back up these direct associations between, let's say, being a fussy person and blood type A.
Where did blood type personality theory come from?
The theory dates back to the early 20th century when scientists in Europe, namely Austrian physician Karl Landsteiner, discovered the ABO blood groups. As was the fashion at the time, scientists quickly applied the new science to infer differences between racial groups, and some speculated that blood type might reflect different inherited traits.
That idea had reached Japan by the 1920s, prompting Takeji Furukawa to write a highly influential paper called "The Study of Temperament Through Blood Type", published in the journal Psychological Research.
Furukawa's paper has since been criticized for being unscientific and methodologically flawed, yet for one reason or another, blood type personality theory deeply resonated with the Japanese public.
Sturdy evidence is scant
For ardent believers, one of the more flattering studies saw researchers from Hirosaki University and Kumamoto University in Japan find a “significant association” between ABO blood groups and certain personality traits.
Published in the journal PLOS One in 2015, the study found that people with ABO blood types had higher scores for “Persistence,” a personality trait that was defined by “industriousness, diligence and stability despite frustration and fatigue”.
However, the researchers themselves concluded by saying the link may be precarious and could be explained by other means.
A deluge of other studies have found no such link. Another Japanese study from 2014 analyzed survey data from over 10,000 people in Japan and the US, concluding blood type explained less than 0.3 percent of the variation in personality. In other words, there is no meaningful relationship between the two.
Similar findings – or lack of findings – have been reported time and time again by researchers from Japan and the rest of the world.
Is blood type personality theory still a thing?
Some signs suggest that belief in blood type personality theory is quietly dying down in Japan.
Ten to 20 years ago, the vast majority of people in Japanese surveys said they believed blood type and personality are tightly related, while more recent polls suggest just 8.3 percent think they are “strongly related”. A further 40.6 percent believe they are “somewhat related”, while over 24 percent answered there is “little” relation between the two.
However, just like armchair astrologers tracking the whereabouts of Jupiter, or cryptozoologists hunting Bigfoot, compelling ideas don’t die easily among certain subcultures, regardless of the evidence against them.
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