Unboxing Japan - Blood Types

Blood types and personality

What do you think of when you hear about personality tests that have become popular in recent years? The most well-known example is probably the 16 Personalities test. However, long before the 16 Personalities test became popular, there was a personality test that is still believed in Japan today. This is the personality test based on blood type.

In Japan, it is not unusual to be asked about your blood type. In a conversation with someone you have just met for the first time, you may be asked “What blood type are you?” This is not a question about race, family background or family lineage — it’s like asking someone their star sign.

Blood type is broadly divided into four categories: A, B, AB, and O (rhesus negative blood types are incredibly rare in East Asia, with only approximately 0.5% of the Japanese population having a negative blood type). According to tradition, type A is a personality that is indecisive, patient, and conscientious, and values duty and honor. Type B is a bold, fearless, and proud personality that is easily absorbed in things but also easily loses interest. Type AB is an artistic, friendly, and multi-faceted personality. Type O is a good listener, broad-minded, stubborn, but kind.

Research and statistics prove that there is no scientific basis for the blood type personality theory, but it is deeply ingrained in Japanese culture nevertheless. This superstition is widely accepted in magazines, TV programs and even everyday conversation. Why do so many Japanese people continue to believe in the link between blood type and personality?

The science behind it (or lack thereof)

The roots of blood type’s connection to personality in Japan can be traced back to a paper published in 1927 by Takeji Furukawa. Furukawa published a paper in the journal Psychological Research entitled “A Study of Temperament Based on Blood Type.” However, this paper was later officially rejected by the Japanese Society of Medicine in 1933 on the grounds that it had no scientific basis.

The book that sparked the blood-type personality diagnosis boom that took place after the war was “Blood Type Compatibility” written by Masahiko Nomi in 1971. However, Nomi's claims were almost on the same level as Furukawa's claims, and it was not a statistically based, mathematically correct analysis, but rather pseudo-science that simply stated assumptions.

Four surveys conducted by Yutaka Matsui in the 1980s collected data on the blood types and personality traits of a total of 12,418 people. Combining this data, Matsui published a paper in 1991 titled “A Statistical Examination of Personality Differences Based on Blood Type”. As a result, no causal or correlative relationship was found between blood type and specific personality traits. As you can see, large-scale surveys like this were already being carried out in the 1980s, and blood type personality diagnosis has been scientifically rejected.

Repeatedly negative data has also been reported around the world. Large-scale surveys in Canada (Cramer & Imaike, 2002), Taiwan (Wu, Lindsted & Lee, 2005), and Australia (Rogers & Glendon, 2003) have all rejected the correlation between blood type and personality. Kengo Nawata collected data on blood type and personality in over 10,000 people from Japan and the United States starting in the year 2000. Nawata also attempted to answer the question of how much of the behavior of the personality scores obtained by blood type could be explained using statistical methods. As a result, it was found that the data obtained by blood type could explain personality only to the extent of 0.3%. In other words, the two were almost completely unrelated.

Blood types as a tool for social communication

From the prevalence and popularity of blood-type personality tests in modern-day Japan, it might be safe to assume that Japanese people are not scientific or logical. But in the strict hierarchies and complex social mores of Japanese culture, blood type personality goes beyond superstition and functions as a tool to facilitate communication between people. Blood type is a popular topic of conversation when meeting someone for the first time, or when talking about human relations at work. In a sense, the topic of blood type is used to help people who don't know each other and have nothing in common to make a good first impression and engage in easy small talk.

Japanese people tend to avoid talking about their own personalities, achievements and boasting. Instead, they are able show their open-mindedness by telling one or two simple episodes along the common topic of blood type.

Conclusion

Foreigners often say that Japanese people are unable to show what they are thinking.

In Japan, expressing your own thoughts takes a backseat to being sensitive to the feelings and way of thinking of another person, which can make conversations with people you don’t know well something of a minefield. It is probably because of this cultural background that a roundabout way of talking about oneself without making a claim is ingrained in all forms of communication.

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