I don't believe that human charactor could be classified by 4 blood types.
But recently I become to believe two typical type of human charactor , cat-type and dog-one.
Human charactor could be classified into only two type , cat and Dog.
I discribe the charactor of cat at first because I love it.

Cat is one of animals that has nature of waiting when they hunt.So they never smell of their own body. And don't want to stay facing wind. Most important thing for them is to hide themselves for fear that being found by their game. It is the wisdom for their life. So everytime they lick their own body all over.
One more thing, they don't move exept in case of necessary.The reson why they can run fast ,jump highly , fight extrordinary on unbelievable level in case of emergency is depend on this charactor of nature. While they have no power of endurance. In short, they store their energy under usual circumstances.
Cat as a pet don't obey us human, keeping their own pace.My pace animal.

On the other hand, dog is completely different from cat.Completely opposite charactor they have .
They tend to hunt together , not alone. And showing teamworks as usual. The smell of their own is not important so they don't take care of themselves , so smell bad . They have toughness and endurance,but lack of quickness in case of emergency being compared to cat.
Dogs as a pet obey us human completely , especialy when they are trained. And show us perfect loyalty that cat never have.

Generaly speaking , dogs and cats tend to hate each other. Similary , Man having charactor of dog tend not to keep good relationship with the man having that of cat ,
I feel.