Introduction

Blood Type Personality Theory

Currently, the effect of genetic factors on personality is estimated to be approximately 50% (Ando et. al., 2004; Gerra et al., 2000; Keller, Coventry, Heath & Martin, 2005). The ABO blood group, discovered by Karl Landsteiner in 1901, is a genetically determined and easily measured biological marker. Hence, much research has been conducted not only on health risks, but also on its impact on personality.
The relationship between blood type and personality is studied at an international scale, and the first academic examination using a statistics base was conducted in 1927 by Takeji Furukawa, a Japanese educational psychologist (Furukawa, 1927 & 1930; Nawata, 2014; Rogers & Glendon, 2003; Sato & Watanabe, 1992; Wu, Lindsted & Lee, 2005). Yet, the epoch that most shapes present-day research is a Japanese book (Nomi, 1971) written by Masahiko Nomi, a Japanese independent researcher, as well as an English book (Nomi & Besher, 1988) written by his son, Toshitaka Nomi, and Alexander Besher (Nawata, 2014; Rogers & Glendon, 2003; Sato & Watanabe, 1992, Wang, 2014).
Masahiko Nomi adopted the multiple method approach (Table 1) which consisted of a) questionnaires on the characteristics of people’s behavior and mindset; b) surveys of blood type distribution for various occupations and specialties; c) observations of people’s behavior and statistical analyses. The sample sizes of these studies were claimed to be tens of thousands of people. He also suggested that there was a d) association with disease and physical constitution, such as the idea that type B was resistant to certain cancers (Nomi, 1978; Shirasa & Iguchi, 1993).