Beginning in approximately 1930, the Japanese embraced the idea of matching personality traits with one's blood type. This phenomenon is as popular in Japan as the idea of matching horoscope with personality is in the United States.
Almost all Japanese are aware of their blood type. The idea began when some in the west were touting the idea that the asian peoples were more closely related to animals then humans, or lower on the evolutionary chain, since type B blood was the predominant blood type in asians and animals. As ludicrous and unscientific as this idea was, it was insulting to say the least. Modern science disproves this obviously faulted idea. In the 1930's Furukawa Takeji (1891-1940) set out to disprove this notion and a new idea was born.
However, the idea of personality traits being influenced by blood type remains. Companies in Japan even had divided workers by blood type.
Here are the general ideas of each blood type. The Rh factor plays no role in the blood type/personality idea:
Type O's are outgoing, and very social. They are initiators, although they don't always finish what they start. Creative and popular, they love to be the center of attention and appear very self confident.
While outwardly calm, they have such high standards (perfectionists) that they tend to be balls of nerves on the inside. Type A's are the most artistic of the blood groups. They can be shy, are conscientious, trustworthy, and sensitive.
Goal oriented and strong minded, type B's will start a task and continue it until completed, and completed well. Type B's are the individualists of the blood group categories and find their own way in life.
Type AB's are the split personalities of the blood groups. They can be both outgoing and shy, confident and timid. While responsible, too much responsibility will cause a problem. They are trustworthy and like to help others.
Compatability by Blood Groups:
A is most compatible with A and AB
B is most compatible with B and AB
AB is most compatible with AB, B, A and O
O is most compatible with O, and AB
To learn about the science of blood types, please research "Blood Groups and Anthropology" "Craig Medical" or "The Franklin Institute."