In his 1954 book, Atlas of Men, Sheldon categorised all possible body types according to a scale ranging from 1 to 7 for each of the three "somatotypes", where the pure "endomorph" is 7–1–1, the pure "mesomorph" 1–7–1 and the pure "ectomorph" scores 1–1–7. From type number, an individual's mental characteristics could supposedly be predicted. Barbara Honeyman Heath, who was Sheldon's main assistant in compiling Atlas of Men, accused him of falsifying the data he used in writing the book. Questions exist about her motivations in making these accusations.
Sheldon's "somatotypes" and their supposed associated physical and psychological traits can be characterized as follows:
Ectomorphic: characterized as linear, thin, fragile, lightly muscled, flat chested and delicate; described as cerebrotonic inclined to desire isolation, solitude and concealment; and being tense, anxious, restrained in posture and movement, introverted and secretive.
Mesomorphic: characterized as hard, rugged, rectangular, athletically built with well developed muscles, thick skin and good posture; described as somatotonic inclined towards physical adventure and risk taking; and being vigorous, courageous, direct and dominant.
Endomorphic: characterized as round and soft with under-developed muscles and having difficulty losing weight; described as viscerotonic enjoying food, people and affection; having slow reactions; and being disposed to complacency.
Sheldon's work was heavily burdened by his racist, anti-Semitic and sexist views. There is evidence that different physiques carry cultural stereotypes. For example, one study found that endomorphs are likely to be perceived as slow, sloppy, and lazy. Mesomorphs, in contrast, are typically stereotyped as popular and hardworking, whereas ectomorphs are often viewed as intelligent but fearful and usually take part in long distance sports, such as marathon running. Stereotypes of mesomorphs are generally much more favorable than those of endomorphs. Stereotypes of ectomorphs are somewhat mixed. Sheldon's ideas that body type was an indicator of temperament, moral character or potential—while popular in an atmosphere accepting of the theories of eugenics—were soon widely discredited. The principle criticism of Sheldon's constitutional theory was that it was not a theory at all but one general assumption, continuity between structure and behavior, and a set of descriptive concepts to measure physique and behavior in a scaled manner. His methodology was also criticized.
Sheldon's theories enjoyed a vogue as the "pop-psych flavor of the month" through the 1950s. Modern scientists, however, generally dismiss his claims as outdated, if not outright quackery. Sheldon's methodology and theories have been extensively criticized and largely discredited.
Sheldon's photographs of naked Ivy League undergraduates, numbered in the thousands, were taken under the guise of a pre-existing program ostensibly evaluating student posture. The photos were in fact collected by Sheldon to provide data for his ideas about somatotypes.
^"Body Type". Encyclopedia of Special Education: A Reference for the Education of Children, Adolescents, and Adults with Disabilities and Other Exceptional Individuals. Wiley. 2007. ISBN9780471678021. Retrieved 2014-11-20 – via Credo Reference. (subscription required (help)).
Gerrig, Richard; Zimbardo, Phillip G. (2002). Psychology and Life (16th ed.). Boston: Allyn and Bacon. ISBN0-205-33511-X.
Hartl, Emil M.; Monnelly, Edward P.; Elderkin, Roland D. (1982). Physique and Delinquent Behavior (A Thirty-year Follow-up of William H. Sheldon’s Varieties of Delinquent Youth). New York: Academic Press. ISBN0-12-328480-5.