William Stern (psychologist)

William Stern (; 29 April 1871 – 27 March 1938), born Wilhelm Louis Stern, was a 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, later used by Lewis Terman and other researchers in the development of the first IQ tests, based on the work of Alfred Binet. He was the father of the German writer and philosopher Günther Anders. In 1897, Stern invented the tone variator, allowing him to research human perception of sound in an unprecedented way.