Blood Types: How Real Are They?

Blood Types: How Real Are They? | English Columnist Erin Ji In Lee

“You’re blood type O? No way. I was sure you were type A!”

I hear this quite often from people I meet for the first time. However as everyone I meet get to know me better, they begin to change their minds and say,

“Nevermind, I see why you’re type O. I can’t believe I didn’t see this side of you the first time we met!”

What does this really mean? We humans like to put ourselves into categories, according to characteristics we are born with such as race and gender, as well as characteristics that we acquire such as occupation and residency. An interesting example of such categorization is blood type. ABO blood types are genetic groups that humans are categorized into at birth. Although completely based on genetic information, blood types are considered an important indicator of a person's personality in some cultures. These cultures assign specific personalities to different blood type groups, with the expectation that some people with certain blood types will  act in particular ways. For instance in Korea, blood type is a common topic of conversation and is often asked about when people are getting to know one another.

Growing up in Korea, I encountered conversations like the one above quite often. Many people expect me to have blood type A, possibly due to my shy and quiet first impression. They seem quite surprised and shocked when I tell them that I actually have blood type O, saying that they saw a “strong side” of blood type A in me and could not imagine me being a blood type O at all. How accurate then, are these categories? ABO blood type groups were originally created from genetic information and are assigned universally to everyone regardless of culture. Yet if their connection to personality traits is only accepted in some cultures, does there exist a relationship between blood types and personality ?

Blood Types: The Biological Explanation

Everyone has an ABO blood type: type A, type B, type AB, or type O. To provide a short biological explanation of how blood types are genetically constructed and passed on, they are simply based on the presence or absence of A and B alleles in our blood cells. As their names suggest, blood type A contains only the A allele or a combination of the A and O alleles, and blood type B contains only the B allele or a combination of the B and O alleles. Blood type AB contains both the A and B alleles, and type O contains only the O allele. When this is passed on genetically, each biological parent donates one allele each to the child. The blood type of the child can be determined from the resulting combination of alleles from each parent. For instance, a child who received the A allele from her mother and O allele from her father has blood type A. How, then, did personality traits become assigned to genetic categories of blood types?

Bloods Types and Personality

The idea that personality is genetically inherited through blood types originated from Japan. A man named Takeji Furukawa was one of the first to bring up this theory, in his study called "The Study of Temperament Through Blood Type”. He aimed to "penetrate the essence of the racial traits of the Taiwanese, who recently revolted and behaved so cruelly." Furukawa found that 41.2% of the Taiwanese had blood type O and used this to explain why the Taiwanese were so rebellious, genetically attributing rebelliousness to blood type O. Despite the lack of credentials and scientific evidence in this study, the idea of associating blood types with personality took off quickly in Japan.

According to the Japanese Blood Type Personality Theory, each blood type defines a person’s personality. This theory does not only exist in Japan but is also adopted by and widely used in the Korean culture. The blood type theory is not only used to classify the personalities of individuals but also to predict whether they different individuals make good matches, either as friends or as significant others. Let us examine some of the most common personality traits associated with each blood group:

Blood Type	Personality Traits
A	timid, shy, neat, sensitive, patient, detail-oriented
B	passionate, selfish, active, strong stance, erratic
AB	talented, unpredictable, artistic, eccentric, proud
O	easy going, confident, unpunctual, leadership, rebellious

Although used dominantly in Japan and Korea, these countries are not alone in assigning personality traits to blood type groups. An article on Waking Times provides a North American perspective on different blood types and the personalities each one represents:

Blood Type	Personality Traits
A	conservative, responsible, cautious, punctual
B	unpredictable, goal-oriented, confident, creative, flexible
AB	understanding, organized, rational, cool, controlled
O	ambitious, confident, sociable, natural leaders

A few similarities are visible, yet there are some glaring contradictions between the two tables. First of all, the Asian cultures define having a strong stance or opinion as characteristic of blood type B, while the North American perspective views individuals with blood type B as flexible. Also, blood type AB is viewed in Asian cultures as unpredictable and eccentric whereas it is viewed as organized and rational in North America.

If blood type groups are common to all humans, why are they considered differently among different cultures? Which one is correct? Who determines this? Given how difficult these questions are to answer, there is no standardized, universal method of associating personality with blood types. In fact, the blood type theory is dismissed by the scientific community as a superstition due to lack of scientific evidence and testable criteria. It is interesting to see that the blood type theory only exists in Japan and Korea, and that even when other cultures do try categorizing personality traits into blood groups, these categories end up quite differently from those created in other cultures. In fact, contradictions exist even within the same culture; as seen in the conversation in the introduction, all of my life I have had people mistaking me for a blood type A based on my apparent personality. The Korean culture I grew up in considers blood type as a common way of defining our personalities. Yet the lack of biological evidence and the lack of consistency between cultures regarding this theory leads me to challenge it: is the theory behind blood types and personalities biologically real, or just a cultural phenomenon?