Blood Type Personality Theory

The blood type personality theory is a pseudoscientific belief prevalent in Japan and South Korea, which states that a person's blood group system is predictive of a person's personality, temperament, and compatibility with others. The theory is generally considered a superstition by the scientific community.

One of the reasons Japan developed the blood type personality indicator theory was in reaction to a claim from German scientist Emil von Dungern, that Blood type B people were inferior. The popular belief originates with publications by Masahiko Nomi in the 1970s.

Although some medical hypotheses have been proposed in support of blood type personality theory, the scientific community generally dismisses blood type personality theories as superstition or pseudoscience because of lack of evidence or testable criteria. Although research into the causal link between blood type and personality is limited, the majority of modern studies do not demonstrate any statistically significant association between the two.Cramer, K. M., & Imaike, E. (2002). Personality, blood type, and the five-factor model. Personality and individual differences, 32(4), 621–626.Rogers, M., & Glendon, A. I. (2003). Blood type and personality. Personality and individual differences, 34(7), 1099–1112.Wu, K., Lindsted, K. D., & Lee, J. W. (2005). Blood type and the five factors of personality in Asia. Personality and individual differences, 38(4), 797–808.Kengo Nawata (2014)
''No relationship between blood type and personality: Evidence from large-scale surveys in Japan and the US''
, The Japanese Journal of Psychology, 85(2), 148–156. Some studies suggest that there is a statistically significant relationship between blood type and personality, although it is unclear if this is simply due to a self-fulfilling prophecy.Sakamoto, A., & Yamazaki, K. (2004)
''Blood-typical personality stereotypes and self-fulfilling prophecy: A natural experiment with time-series data of 1978–1988.''
, Progress in Asian Social Psychology, Vol. 4, 239–262.Yamazaki, K., & Sakamoto, A. (1992), 血液型ステレオタイプによる自己成就現象II－全国調査の時系列分析－ ''The self-fulfillment phenomenon generated by blood-typical personality stereotypes: time-series analysis of nation-wide survey II'', Paper presented at the 33rd annual convention of the Japanese society of social psychology. Tokyo (pp. 342–345).Cosy Muto, Masahiro Nagashima et al. (2011)
A Demonstrative and Critical Study on Pseudo-science for Scientific Literacy Construction at Teacher Education Course
FY2011 Final Research Report from the Database of Grants-in-Aid for Scientific Research - neither exact number of samples nor years was specified in the report

History

The idea that personality traits were inherited through the blood dates as far back as Aristotle., cited in Hippocrates also sought to link personality biologically, linking traits with the four bodily humors – sanguine, phlegmatic, choleric, and melancholic.

In 1926, Rin Hirano and Tomita Yashima published the article "Blood Type Biological Related" in the ''Army Medical Journal''. It was seen to be a non-statistical and unscientific report motivated by racism.

Takeji Furukawa

In 1927, Takeji Furukawa, a professor at Tokyo Women's Teacher's School, published his paper "The Study of Temperament Through Blood Type" in the scholarly journal ''Psychological Research''. The idea quickly took off with the Japanese public despite Furukawa's lack of credentials, and the militarist government of the time commissioned a study aimed at breeding ideal soldiers. The study used ten to twenty people for the investigation, thereby failing to meet the statistical requirements for generalizing the results to the wider population.

On the other hand, in 1934, Fisher announced the chi-squared test, which is very popular at present, for the first time. Several scholars said that they found statistically significant differences in analyzing Japanese work conducted at that time.

In another study, Furukawa compared the distribution of blood types among two ethnic groups: the Formosans in Taiwan and the Ainu of Hokkaidō. His motivation for the study appears to have come from a political incident: After the Japanese occupation of Taiwan following Japan's invasion of China in 1895, the inhabitants tenaciously resisted their occupiers. Insurgencies in 1930 and 1931 resulted in the deaths of hundreds of Japanese settlers.

The purpose of Furukawa's studies was to "penetrate the essence of the racial traits of the Taiwanese, who recently revolted and behaved so cruelly." Based on a finding that 41.2% of Taiwanese samples had type O blood, Furukawa assumed that the Taiwanese rebelliousness was genetic. His reasoning was supported by the fact that among the Ainu, whose temperament was characterized as submissive, only 23.8% is type O. In conclusion, Furukawa suggested that the Japanese should increase intermarriage with the Taiwanese to reduce the number of Taiwanese with type O blood.

Masahiko Nomi

Interest in the theory was revived in the 1970s with a book by Masahiko Nomi, a journalist with no medical background (he graduated from the engineering department of the University of Tokyo). Few Japanese psychologists criticized him at that time, so he continued to demonstrate statistically significant data in various fields and published several books with these results. Later after his death in 1981, Masahiko Nomi's work was said to be largely uncontrolled and anecdotal, and the methodology of his conclusions was unclear. Because of this, he was heavily criticized by the Japanese psychological community, although his books remain popular. His son, Toshitaka Nomi, continued to promote the theory with a series of books and by running the Institute of Blood Type Humanics. He later established th
Human Science ABO Center
for further research and publication in 2004.

Background and criticism

Criticism

Kengo Nawata, a Japanese social psychologist, statistically analyzed three data sets of over 10,000 Japanese and American people in total. However, 65 of the 68 items yielded non-significant differences between blood types and the other three items showed relatively slight relationships. Therefore, the blood type explained only 0.3% of the whole differences of these data sets. This result suggests that blood type explained very little of people's personalities. Nawata concluded that there is no relevance of blood type for personality.

Controversial statistically significant data

However, some academic researchers have shown several statistically significant data in Japan and Korea. Akira Sakamoto and Kenji Yamazaki, Japanese social psychologists, analyzed 32,347 samples of annual opinion polls from 1978 through 1988. These results indicated that Japanese blood-typical stereotypes influenced their self-reported personalitieslike a self-fulfilling prophecy.

Cosy Muto and Masahiro Nagashima et al. (Nagasaki University) conducted a supplementary survey of Yamazaki and Sakamoto in 2011. They demonstrated that significant and the same difference in personalities between blood-types by using the same database as Samamoto and Yamazaki used. In the 1990s, the difference due to blood types was stabilized and variances became smaller. Then in the 2000s, the difference was statistically significant, too. However, the effect magnitude was extremely small, despite 'significance' in the statistical sense.

Another Japanese social psychologist, Shigeyuki Yamaoka (Shotoku University), announced results of his questionnaires, which were conducted in 1999 (1,300 subjects)Shigeyuki Yamaoka (1999), 血液型ステレオタイプが生み出す血液型差別の研究 A Study on Blood Harassment Caused by Blood-typical Stereotypes, Paper presented at the 40th annual convention of the Japanese society of social psychology. Tokyo. For further information of this paper, confer to Shigeyuki Yamaoka (2001), ダメな大人にならないための心理学 A Psychology Book for not to Become a Useless Adult, pp. 35–73 and 2006 (1,362 subjects),Shigeyuki Yamaoka (2006)
血液型性格項目の自己認知に及ぼすＴＶ番組視聴の影響 Influence of Watching TV programs to One's Self-recognition of the Blood-type personality Items
Paper presented at the 47th annual convention of the Japanese society of social psychology. Tokyo. In both cases, the subjects were university students, and only subjects with enough knowledge of and belief in the "blood-type diagnosis" showed meaningful differences. He concluded that these differences must be the influence of mass media, especially TV programs. Yamaoka later examined 6,660 samples from 1999 through 2009 in total and found the same result.Shigeyuki Yamaoka (2009)
血液型性格判断の差別性と虚妄性(自主企画(2)) Segregation and falsehood of blood-type personality analysis
self planning session (2) at the 18th annual convention of the Japanese society of personality psychology.

On the other hand, there are opinions that the statistically meaningful differences according to the blood types are not explained only by beliefs, nor are they a self-fulfilling prophecy. In Japan, the penetration rate of blood-typical personality traits was investigated. Yoriko Watanabe, a Japanese psychologist (then Hokkaido University), chose "well-known" traits and found most traits were known to no more than half of Japanese (subjects were university students).Watanabe, Y. (1994)
血液型ステレオタイプ形成におけるプロトタイプとイグゼンブラの役割 The roles of prototype and exemplar in the formation of the "blood type stereotype"
. Japanese Journal of Social Psychology, 10–2, 77–86. She extracted 7 traits for each 4 blood types, 28 in total, which were common to three or more "blood type diagnosis" books. 20 items of all 28 showed less than 50% penetration (the average is 46.1%). A Japanese writer, Masayuki Kanazawa, analyzed these blood-typical traits in combination with data from Yamaoka (1999) that used the same items of Watanabe's penetration survey. If blood-typical differences are caused by penetration (or their self-recognition), the rate of differences of a trait is proportional to the rate of its penetration. However, Kanazawa was not able to discover any association with blood-type differences and penetration rates. This result raises doubt about the role of beliefs and self-fulfilling prophecy.

Most reports that demonstrated statistical correlation attribute differences to a self-fulfilling prophecy. However, no study directly proved the existence of "self-fulfillment". Therefore, the opinions of researchers are varied at present:
# Whether there is a statistical correlation or not;
# Whether any statistical correlations are superficial, being caused by subjects' self-fulfilling prophecy, or if they are truly caused by the blood type.

In a 2021 Japanese study, ANOVA results of a 6,000-population large-scale survey showed that respondents displayed the personality traits corresponding to their own blood type more strongly than respondents who had different blood types did. This finding was consistent across all traits, and all differences were statistically significant. The same differences in scores were found in the groups who reported no blood type personality knowledge, although the values were smaller.Kanazawa, M. (2021)
A Pilot Study Using AI for Psychology: ABO Blood Type and Personality Traits
. American Journal of Intelligent Systems, 11(1), 7–12.

Blood-type personality and the five-factor model

The five-factor model tests were carried out in several countries, including Japan, Korea, and Taiwan, after the year 2000. These tests were intended to digitize self-ratings of the "big five" personality traits. It was expected that differences in self-reported personalities (a self-fulfilling prophecy) would be detected from the subject who believed in blood-typical stereotypes. As a result, researchers found no meaningful statistical difference.So Hyun Cho, Eun Kook M. Suh, Yoen Jung Ro (2005)
''Beliefs about Blood Types and Traits and Their Reflections in Self-reported Personality''
, Korean Journal of Social and Personality Psychology, 19(4), 37–47.

So Ho Cho, a Korean psychologist (Yonsei University), and the others carried out a questionnaire about blood-typical items to subjects and discovered statistical differences as expected. However, the difference was not found when the five-factor model for big five personality traits was administered to the same subjects. Another Korean researcher Sohn (Yonsei University) re-analyzed Cho's data.Sung Il Ryu, Young Woo Sohn (2007)
''A Review of Sociocultural, Behavioral, Biochemical Analyses on ABO Blood-Groups Typology''
, The Korean Journal of Social and Personality Psychology He found that several independent items of the big five personality test detected differences according to each blood-typical stereotype. However, these differences became extinct in the process of plural items being gathered to five factors (big five). If these results are correct, the five-factor model test cannot detect differences between the blood types – if such a causal link did indeed exist.

In 2014, a Korean matchmaking company 듀오 Duo conducted a research survey closely examined 3,000 couples and found that blood type had no significant impact on the possibility of a couple getting married.

In 2017, a meta-analysis of studies, using the Big Five personality test, involving 260,861 subjects found that six genes affected human personality. However, the coefficient of determination was as low as 0.04%. This is usually considered to be an error.

Studies of blood distribution in various fields

In order to avoid the influence of "contamination by knowledge", a Japanese psychologist group published a series of studies, but no significant differences were found except for Japanese prime ministers. Later, it was reported that significant differences were found not only for prime ministers, but also for foreign ministers, education ministers, professional baseball hitters, and soccer players in Japan.

Brain waves and light topography

Kim and Yi (Seoul University of Venture & Information) measured the brain waves of 4,636 adults. They reported that type O people were most stress-resistant. Moreover, an experiment using light topography instruments by Munetaka Haida (Tokai University School of Medicine) suggests the possibility that activated parts of the human brain are different according to blood types. i.e. type A's left brain is superior to the right, while type B's right brain is superior.

Popularity

In Japan, discussion of blood types is widely popular in women's magazines as a way of gauging relationship compatibility with a potential or current partner. Morning television shows feature blood type horoscopes, and similar horoscopes are published daily in newspapers. The blood types of celebrities are listed in their infoboxes on Japanese Wikipedia. A series of four books that describe people's character by blood type ranked third, fourth, fifth, and ninth on a list of best-selling books in Japan in 2008 compiled by Tohan Corporation.

No less than two-thirds of people in several East Asian countries and areas, such as Japan, Korea, and Taiwan, believe in the association between blood types and personality.

Furthermore, according to one Japanese survey, more than half of Japanese people are fond of talking about blood type and personality.Reiko Yamashita (2008)
血液型性格判断はなぜすたれないのか why doesn't blood type in Japanense culture detariorate?
, Paper presented at the 48th annual convention of the Japanese society of social psychology. The research also says that people in Japan like blood-typical personality diagnosis and 1. talk about it with proper knowledge, 2. believe some relationships exist between blood type and personality, 3. feel its traits apply to themselves to a certain degree. The results of the two other surveys are the same.The following are results of two Japanese surveys:
* Yahoo! Research (December 25, 2008)『「血液型本」に関する調査』 A survey about "blood type books" – "My personality is appropriately expressed so that sympathized, convinced" (66%), "Can grasp my personality objectively with new discovery" (59%), "One of the means and the methods to express my personality" (50%), "Useful in acquaintances" (48%) and "Useful in love-affiliated things" (47%).
* Yumiko Kamise, Yutaka Matsui (1996), 血液型ステレオタイプ変容の形 ―ステレオタイプ変容モデルの検証― Changing processes of stereotype on blood-groups, Japanese Journal of Social Psychology, 11–13, 170–179. – "blood-typical personality diagnosis is a fun" (83.6%), "I like blood-typical personality diagnosis" (61.5%).

Although there is no proven correlation between blood type and personality, it remains popular with the many matchmaking services that cater to blood type. In this way, it is similar to the use of astrological signs, which are also popular in Japan. Asking one's blood type is common in Japan, and people are often surprised when a non-Japanese does not know their blood type.In Japan, you are what your blood type is
''Japan Today''

It is common among anime and manga authors to mention their characters' blood types and to give their characters blood types to match their personalities. Some video game characters have known blood types. Also, it is common for video game series to allow for blood type as an option in their creation modes.

After then-Reconstruction Minister Ryu Matsumoto's abrasive comments towards the governors of Iwate and Miyagi forced him to step down from his post, he partially blamed his behavior on his blood type, saying "My blood is type B, which means I can be irritable and impetuous, and my intentions don't always come across."

Blood types are important in South Korea as well. The Korean webcomic '' A Simple Thinking About Blood Type'' depicts the stereotypes of each blood type and has been adapted as a short anime series in Japan as ''Ketsuekigata-kun!'' in 2013 and 2015.

Discrimination

Blood type harassment, called (wasei-eigo: a portmanteau

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