Heymans' cube

[1][2] He used questionnaires he sent to all General Physicians in the Netherlands and went through many biographies of famous people, like Multatuli and Napoleon.

[3] He also did research into the differences in, what he called, secondary effects using visual stimulation, like bright light.

[4] Based on his research he put people on three dimensions which together formed eight different character types (see figure).

Heymans' character cube was very popular and had a lasting influence on the later-formed field of personality psychology.

[3] Typologies like this constituted the beginning of characterising personality as a unity of psychological traits which can be researched scientifically.