I’ve discussed a number of psychologists in the book. Here are some 20th-century psychologists who were particularly influential and are discussed in the book. For contemporary psychologists, see the page on this site devoted to contemporary research laboratories in personality psychology.

1. A. A. Roback, one of the founders of personality psychology, who reviewed centuries of thought as to how human beings differed from one another.
2. Gordon Allport, another founder of personality psychology, who spoke of personality as a system of neuropsychological systems and the behaviors they bring about.
3. Sigmund Freud
4. Betram Forer