William Stern
The psychologist that may have unknowingly helped spur the Terman intelligence movement in the United States created the famous intelligence quotient. He found it by taking the mental age of a subject divided by their chronological age, then multiplying it by a factor of 100. The average performance of any IQ test is given a score of 100. Many criticize Stern for following a philosophy that was furthered established by his concept of the intelligence quotient, personalism. Otherwise he would be known as one of the primary psychologists in the study of intelligence.