c.400 BCE Ancient Greek physician Hippocrates suggests personality depends on the levels of the four humors in the body.
1946 Raymond Cattell begins developing his 16-factor model of personality.
1961 American psychologists Ernest Tupes and Raymond Christal propose the first “Big Five” personality-factor model.
1975 Hans J. Eysenck’s Personality Questionnaire identifies two biologically based, independent dimensions of personality.
1980 US psychologists Robert Hogan, Joyce Hogan, and Rodney Warrenfeltz develop comprehensive personality tests based on the “Big Five” model of personality.
Until the late 1960s, ...