In the early 20th century, a mother and daughter began work on what is now the world’s most widely used personality test.
The beginnings The Myers-Briggs Type Indicator, the most widely used personality test in the world today, is based on the theory of psychological types that Carl Jung described in his 1921 book, "Psychologische Typen." Jung is pictured at the bottom right in a 1908 group photograph of psychologists. Sigmund Freud sits at the bottom left. © Bettmann/Corbis Buy Photo