The blood type personality theory is a pseudoscientific belief prevalent in East Asia that a person's blood type 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.Takeji Furukawa (1927), 血液型と気質 Blood Type and Temperament - in Europe, type A was more common than type B, while in Asia type B was more prevalent. Von Dungren claimed A people are superior to B people. Because Asia had more B people than some parts of Europe, the inference was that Asia was inferior (along with European B's) A Japanese scholar, Takeji Furukawa, opposed that idea and asserted that B persons were active while A persons were passive. 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. Despite the fact that 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. 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. Neither an exact number of samples nor years was specified in the report.
Overview According to popular belief, people with type A blood are friendly and kind but also obsessive and anxious, people with type B are spontaneous and creative but can be selfish, and people with type O are confident but stubborn and aggressive. In a logical extension of this system, those with type AB are a mix of stereotypical A and B traits, while also being seen as mysterious or aloof due to their relatively low population in Japan. The minority types B and AB are more likely to be negatively stereotyped than A or O.
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, Hayashi Hirano and Tomita Yajima published the article "Blood Type Biological Related" in the Army Medical Journal.
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. Several scholars said that they found statistically significant differences in analyzing Japanese work conducted at that time.e.g. Masao Omura (Nihon University) in "血液型と性格 Blood Type and Personality", Terumitsu Maekawa (Asia University) in "血液型人間学 Blood Type Humanics" and so on.
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,Toshinori Shirasa & Takuji Iguchi (1993), 血液型性格研究入門 血液型と性格は関係ないと言えるのか An introduction to Blood Type Personality Research – Can we say there is no relationship with blood type and personality?, pp. 209–212, 242–243. Virtually no papers nor books about blood type and personality was published from the Japanese psychological community before Masahiko Nomi's death in 1981. so he continued to demonstrate statistically significant data in various fields and published several books with these results.Masahiko Nomi analyzed various data by using statistical methods and found meaningful traits; the following are some of his works. Blood Type Affinity Study 5/1974 – 20,000 samples analyzed in total Blood Type Sports Study 10/1976 – 1,000 track-and-field athletes analyzed Blood Type Essence 6/1977 – listed over 1,000 people (politicians, CEOs, artists, etc.) Blood Type Politics Study 6/1978 – 2,000 politicians analyzed (all representatives of the national Diet, all governors, and all mayors) 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 the Human Science ABO Center for further research and publication in 2004.
Background and criticism
Criticism Kengo Nawata, a social psychologist, studied blood type correlations in a survey of 68 personality traits given to over 10,000 people from Japan and the US. His statistical analysis found that less than 0.3% of the total variance in personality was explained by blood type.
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.
On the other hand, some believe that the statistically meaningful differences according to the blood types are not explained only by beliefs, nor that they are a self-fulfilling prophecy. In Japan, the penetration rate of blood-typical personality traits was investigated. Yoriko Watanabe, a psychologist at Hokkaido University, chose "well-known" traits and found most traits were known to no more than half of Japanese people (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 of 4 blood types which were common to three or more "blood type diagnosis" books. 20 items of all 28 showed less than 50% penetration (the average was 46.1%). A Japanese writer, Masayuki Kanazawa, analyzed these blood-typical traits in combination with data from Yamaoka (1999) that used the same items from 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.Masayuki Kanazawa (2014), 統計でわかる血液型人間学入門 An Introduction to Blood Type Humanics - Understanding by Statistics, Gentosha Runaissance pp. 16–36 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.
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.Yoshio Kubo, Yukiko Miyake (2011), 血液型と性格の関連についての調査的研究 Correlation between blood types and personalities Bulletin of Kibi International University (Department of Social Welfare), 21, 93–100.