Clark Hull grew up handicapped and contracted polio at the age of 24, yet he became one of the great contributors to psychology. His family was not well off so his education had to be stopped at times. Clark earned extra money through teaching. Originally Clark aspired to be a great engineer, but that was before he fell in love with the field of Psychology. By the age of 29 he graduated from Michigan University. When Clark was 34 when he received his Ph.D. in Psychology at the University of Wisconsin in 1918. Soon after graduation he became a member of the faculty at the University of Wisconsin, where he served for 10 years. Although one of his first experiments was an analytical study of the effects of tobacco on behavioral efficiency, his life long emphasis was on the development of objective methods for psychological studies designed to determine the inderlying principles of behavior.