The Origins Of The Blood Type Personality Theory

All over the world, people have devised ways to predict your personality type. There’s the Western zodiac, dating back to ancient Babylonia, and many newspapers still circulate horoscope columns based on this zodiac. The Chinese zodiac also outlines 12 different personality types. There are even modern tests for people to discover their personality type, such as the Myers-Briggs personality assessment.

Other systems determine that personality traits are based on your body, such as finger length or thumb shape. Then there is a blood type personality. Some people believe you can determine your temperament through a blood test, making it a personality test as well as a test for nutritional deficiencies and diseases.

If you’re not familiar with Asian culture, you may not have heard of a blood-type personality. Yet this way of categorizing people by personality is quite popular in some Asian countries, particularly Japan and South Korea. In fact, most people in Japan know their blood type. So, what is the blood type personality theory, anyway?

What is a blood type?

Blood types are determined by the presence or absence of certain antigens in your blood cells. These antigens trigger an immune response if they’re foreign to the body. Before the discovery of blood types, blood transfusions were much riskier. If the donor’s blood had different antigens than the recipient’s, the recipient’s blood could react against the new blood, often causing death. The discovery of blood types revolutionized blood transfusion practice, enabling doctors to sort blood types by blood group and give patients a transfusion from compatible blood. Blood typing is now a normal part of the blood transfusion process.

On its face, blood type seems to have nothing to do with personality traits. Yet since their discovery, blood types have been used to categorize people beyond compatible blood donors. For example, the Nazis used the findings to justify German superiority, declaring that A and O types (more common among Germans) were superior to B types (more common among Jews and other ethnic groups). As each of the four blood groups occurs in all human populations, this idea was demonstrably false. However, beliefs about the relationship between blood type and personality persist.

The blood type personality theory

While an Austrian scientist discovered blood types in 1901, the idea of “blood type personality” didn’t come about in Europe or North America. Rather, it was a professor at a Tokyo women’s teaching school who introduced the idea in 1927. Takeji Furukawa's professor backed up his theory with evidence from observations of his own family, and he published his findings in a scholarly journal.

The blood types and their personality traits

The blood type personality theory determines personality traits based on the four blood types: A, B, O, and AB. The theory is sometimes known as ABO blood type personality, covering the four main categories. According to blood type personality theory, one’s blood type can determine their temperament, behaviors, compatibility with other blood types, and even their suitable career paths.

A blood type personality

People with blood type A are said to be well-organized, reserved, earnest, and responsible. On the other hand, blood type A personalities tend to be nervous and a bit stubborn. The blood type A personality is the most common in Japan, with about 40% of the population with this blood type. Type As often get along well with others, but this may come at the expense of their own well-being. The recommended careers primarily cover those that require little human contacts, such as programming, accounting, writing, and research. As for their ideal blood type partner, people with blood type A are most compatible with their own type or ABs.

B blood type personality

On the other hand, blood type Bs are known to be curious, creative, and outgoing. On the negative side, they can sometimes be irresponsible and indecisive. Type Bs’ outgoing personality makes it easy for them to be around people a lot of the time, as socializing doesn’t wear them down. Careers as leaders or working with lots of people are recommended for type Bs. Those seeking partners would be most compatible, just as with Type As, with their own type or ABs.

Universal donor/O blood type personality

People with blood type O are considered optimistic, easygoing, and confident. Their negative personality traits include being rude, vain, or self-centered. Their confident natures also make Os good leaders, and they are said to be physically strong. For example, people with O type are said to be good baseball players. Once again, Os should be most compatible with their own type or with type ABs.

Universal recipient/AB blood type personality

AB blood type personalities tend to be eccentric, as the blood type personality theory blends the traits from type A and type B for this type. People with AB blood type can be sociable and shy, rational and a dream-chaser, mysterious and charming. Negative personality traits include impatience and forgetfulness. AB is the rarest blood type, so an AB/AB pairing is said to be something truly special. However, AB types apparently can get on with any other blood type.

The blood type books examining the relationship between blood type and personality get into much more detail about each blood type personality. Like many personality tests, literature about blood type personality theory uses general descriptive language, painting each blood type personality with broad strokes while remaining personal and specific. And just as with horoscopes, these blood-type personalities remain personally relevant and convincing to many people.

Why do the Japanese think about blood type so much?

So, what is with the obsession with blood types and personality in East Asia? The blood type personality theory may be so popular in Asia is because it originated there. The colonial Japanese government used Furukawa’s idea of blood type personality to create better soldiers as they expanded their empire in the 1930s. However, the Imperial Army’s research went nowhere, and the connection between blood type and personality was discounted.

The theory was repopularized by journalist Masahiko Nomi, who published several books about blood types, including bestsellers Understanding Affinity by Blood Type in 1971 and Blood Type Humanics in 1973. While Nomi’s evidence was heavily anecdotal and his findings faced criticism from reputable psychologists, his blood-type books were hugely popular. To this day, the blood type personality theory remains popular in Japan. The blood type personality theory has taken a downturn in recent years, but the fascination with blood types continues.

In Japan, the blood type personality theory is so popular that some people organize their blood type. They may refuse to date a seemingly incompatible blood type, seek a relationship or dating service based on blood type, and even follow a blood type diet. People’s belief in blood type personality and other less-than-scientific forms of personality determinants may result from confirmation bias. If you know what a certain blood type personality is supposed to be, you might look for those traits in someone when they reveal their own blood type to you.

The popularity of blood type personality theory in East Asia, particularly Japan, may also lie in the fact that these countries are ethnically homogeneous. The vast majority of Japanese people are of the same ethnicity, so categorizing people by looks can only go so far. However, blood type, while invisible, does differ and has become a convenient marker of difference. This connection between blood type and personality shows how people can find ways to categorize and stereotype each other.

Problems with blood type personality

The idea that blood types determine personalities seems like a harmless idea on the surface. Looking at blood type horoscopes and taking your blood type personality can be a fun diversion. But beliefs about blood types, especially in Japan, aren’t light fun but taken very seriously. Sometimes, people experience discrimination for their blood type, from school to relationships to jobs. This problem is so common in Japan it’s given a name: “blood harassment.” People with blood types B and AB, which are less common in Japan, are particularly prone to experiencing blood type harassment and prejudice.

There are also the problematic applications of the blood type personality theory, going back to the originator of the idea, Takeji Furukawa. His later studies suggest a rather unscientific racial bias. Furukawa went on to study the relationship between temperament and blood type as a part of an analysis of “essential racial traits” of Taiwanese people, many of whom were resisting colonial rule by Japan. From the sample, it was found that about 40% of Taiwanese had blood type O, and Furukawa came to the conclusion that their rebelliousness was linked to their blood type.

Similar to race, a person’s blood type is innate and unchangeable. Coupling that with its early adoption in eugenicist regimes such as Nazi Germany and Imperial Japan, the blood type personality theory isn’t quite as harmless as it seems. Like race, age, and gender, blood type can be stereotyped and prejudice believers in blood type personality against certain blood types, resulting in the harmful discrimination and blood type harassment seen in Japan.

Real science or pseudoscience?

Nomi wrote Blood Type Humanics, had no medical background and offered up purely anecdotal research. So, while beliefs about blood type personalities persist, there is no clear connection between blood type and personality.

One problem with the blood type personality theory and other personality theories is that, unlike our blood type, personality is not a fixed trait. Someone outgoing at work may actually be quite shy in social situations, and the workplace structure helps them socialize. Other people may be rather creative, but their school or work responsibilities don’t reflect their creativity, and it’s instead used for hobbies or personal projects. Still, others may not seem particularly curious or social in certain settings, but they’re the most talkative and enthusiastic in the group in others. A person’s personality is prone to change based on whom they’re interacting with: people act differently around each person in the family at home than their colleagues at work, with their friends on a night out, then strangers on the street, and so on. So, it’s best not to base your life around personality types. Even your own so-called blood type personality may not be a perfect match.

Only one thing is for sure: your blood type only determines what kind of blood you can receive and to whom you can give your blood. Your blood type has nothing to do with your personality whatsoever. If you’re having relationship problems or issues at work, knowing your blood types, zodiac signs, or index finger length will not solve them. It’s best to follow proven, evidence-based approaches to making important decisions and solving problems.

If you’re experiencing personality clashes, discrimination, or any other kind of interpersonal problem, confiding in trusted friends or colleagues can help you overcome them. Some issues can be particularly difficult to work out on your own, and there’s no shame in seeing a therapist. The mental health professionals online at Regain, for example, can help you work through all of life’s challenges. 

Takeaway

Just as Western zodiac signs aren’t factual determiners of personality, so are blood-type personality traits. It can be a fun diversion to read blood-type horoscopes or a trivia fact about your favorite celebrity. Still, blood type is not a clear predictor of personality, nor should anyone base their entire lives around it. If it gives people structure and purpose to hold these beliefs, this is fine. But such beliefs can also close your mind to relationships and opportunities that you could otherwise pursue, so be sure to strike the right balance.