William Stern

German psychologist and philosopher noted as a pioneer in the field of the psychology of personality and intelligence. He was the inventor of the concept of the intelligence quotient, or IQ, the practice of dividing the developmental age by the chronological age.

Stern was considered in his time as a leading youth psychologist and one of the foremost authorities in differential psychology. Stern's philosophy, which is laid down in several voluminous books, was expressed as a form of personalism.

Stern was in 1904 a founding member of the "German Society for Psychology" and the Journal of Applied Psychology.

In 1897, Stern invented the tone variator, allowing him to research human perception of sound in an unprecedented way.

In 1933, because of the Nazi regime, he and his wife had to fled, first to the Netherlands and later to the USA. He died at age 66 on 27 March 1938 in Durham, North Carolina, of heart failure.