Supplement 1

Personality tests cannot detect blood-type differences properly

Psychology personality tests cannot detect correct differences of personality by blood types.

Researchers often use a famous personality test called "Big Five." This test cannot detect correct differences, though used globally. After all, to analyze relationship of blood types and personality, current personality tests might be powerless.
Papers that used Big-Five test are as follows.  No or little difference found (*1) or inconsistent results (*2). 

The followings are written only in Japanese.

  • 川名好浩(川村学園女子大学)血液型性格判断 -Big Five でのプロフィール- 日本心理学会第67回大会論文集 p156 (2003) *1
  • 森圭一郎・原野睦生・江藤義典・津田彰・内村直尚(久留米大)・中川康司(奈良県医大)TCIとBig5による性格とABO式血液型の関連解析 日本生物学的精神医学会プログラム・講演抄録 第27巻 p306 (2005) *1
  • 久保義郎・三宅由起子 血液型と性格の関連についての調査的研究 吉備国際大学研究紀要(社会福祉学部)第21号 p93-100 (2011) *1
  • 清水武・石川幹人 ABO式血液型と性格との関連性―主要5因子性格検査による測定 (2011) *2

Reanalysis of global Big-Five surveys is discussed in the following Korean paper.


Sung Il Ryu, Young Woo Sohn (2007). A Review of Sociocultural, Behavioral, Biochemical Analyzes on ABO Blood-Groups Typology. Korean Journal of Social and Personality Psychology, 21 (3), 27-55


In this paper, Dr. Sohn said,


We concluded that blood types and personality are not related in all studies that used the Big-Five Factor model (So Hyun Cho, 2005; Cramer, 2002; Rogers, 2003; Kunher, 2005).

Then we get the survey data from So Hyun Cho (2005) and reanalyzed individual question items in detail.  Significant relations with blood types were found in 10 items (within a red line).

Obviously, the Big-Five model cannot detect actual blood-type differences. In other words, differences in individual "blood-type-characteristic" questions must have appeared, but they had been canceled out in the process of consolidating the results into five factors. Some differences might have decreased and the others might have disappeared ...

Dr. So Hyun Cho also said in his paper (2005)


Participants also rated their own personality on two different measures - the Big 5 inventory and a set of personality traits most frequently associated with each of the 4 blood types (stereotypic traits). Consistent with past research, no meaningful relationship emerged between the Big 5 traits and blood type. Interestingly, however, self-ratings on the stereotypic traits revealed a self-fulfilling pattern. Those who firmly believed in the validity of the blood type stereotypes were more likely to report his/her trait in a stereotype-consistent direction (e.g., a blood type A person reports that she indeed is very "timid").


As mentioned before,


Results of self-report-type questionnaires are usually considered as "personality itself" (not only "recognition of self's personality").

Source: Toshinori Shirasa & Takuji Iguchi, An Introduction to blood-type personality research (1993) 白佐俊憲・井口拓自 血液型性格研究入門―血液型と性格は関係ないと言えるか


A deep sigh ... 


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