The term somatotype refers to the three body types. The concept of somatotypes was developed in the 1940s in conjunction with Constitutional psychology as a theory by American psychologist William Herbert Sheldon, whereby he associated body types with human temperament types. The terms endomorphic, mesomorphic and ectomorphic are still used on occasion to describe body types, usually in conjunction with exercise programming for a specific body type, but interest in this kind of correlation between physiology and psyche has fell out of favor for being considered outdated.