Blood type personality theory
[2][5][6] 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.
[7][8][9][10] 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.
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.
[15] In 1926, Hayashi Hirano and Tomita Yajima published the article "Blood Type Biological Related" in the Army Medical Journal.
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.
[2] 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.
[16] 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:[17] After the Japanese occupation of Taiwan following Japan's invasion of China in 1895, the inhabitants tenaciously resisted their occupiers.
[17] 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."
[17] 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,[18] so he continued to demonstrate statistically significant data in various fields and published several books with these results.
[20] His son, Toshitaka Nomi, continued to promote the theory with a series of books and by running the Institute of Blood Type Humanics.
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.
Akira Sakamoto and Kenji Yamazaki, Japanese social psychologists, analyzed 32,347 samples of annual opinion polls from 1978 through 1988.
Cosy Muto and Masahiro Nagashima et al. (Nagasaki University) conducted a supplementary survey of Yamazaki and Sakamoto in 2011.
[24] A Japanese writer, Masayuki Kanazawa, analyzed these blood-typical traits in combination with data from Yamaoka (1999)[21] that used the same items from Watanabe's penetration survey.
[7][8][9][27][28] 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.
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.
[40] One survey showed that at least two-thirds of respondents from Chinese-speaking East Asian countries and regions believe in an association between blood types and personality.
