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Constitutional psychology is a theory, developed in the 1940s by American psychologist William Herbert Sheldon, associating body types with human temperament types. Sheldon proposed that the human physique be classified according to the relative contribution of three fundamental elements, somatotypes, named after the three germ layers of embryonic development: the endoderm, (develops into the digestive tract), the mesoderm, (becomes muscle, heart and blood vessels), and the ectoderm (forms the skin and nervous system).

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.

The three typesEdit

Sheldon's "somatotypes" and their supposed associated physical traits can be summarized as follows:

  • Ectomorphic: characterized by long and thin muscles/limbs and low fat storage; usually referred to as slim. Ectomorphs are not predisposed to store fat or build muscle.
  • Mesomorphic: characterized by medium bones, solid torso, low fat levels, wide shoulders with a narrow waist; usually referred to as muscular. Mesomorphs are predisposed to build muscle but not store fat.
  • Endomorphic: characterized by increased fat storage, a wide waist and a large bone structure, usually referred to as fat. Endomorphs are predisposed to storing fat.

The idea that these general body-types may correlate with general psychological types did not originate with Sheldon. In general outline, it resembles ideas found, for instance, in the tridosha system of Ayurveda; The Republic, by Plato; and propounded in the twentieth century by George Gurdjieff. In addition, Friedrich Nietzsche writes that "nature ... distinguishes" three different physiological body types, which correspond to a Republic-esque hierarchy.[1]

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.[2] Stereotypes of mesomorphs are generally much more favorable than those of endomorphs. Stereotypes of ectomorphs are somewhat mixed.

The three body type descriptions could be modulated by body composition, which can be altered by specific diets and training techniques. In a famine, a person who was once considered an endomorph may begin to instead resemble an ectomorph, while an athletic mesomorph may begin to look more like an endomorph as he or she ages and loses muscle mass. [citation needed]

However, some aspects of the somatotype cannot be changed: muscle and adipose mass may change but the bone structure is a fixed characteristic. In the same way, cultural conditions might mask a tendency to one or another temperament. [citation needed]

Modern assessmentsEdit

Sheldon's theories enjoyed a vogue as the "pop-psych flavor of the month" through the 1950s.[3] Modern scientists, however, generally (with occasional exceptions[4][5], some relying on outdated – 1978 or prior – studies) dismiss his claims as outdated, if not outright quackery.[6]

Sheldon's photographs of naked Ivy League undergraduates, numbered in the thousands, were taken under the umbrella 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. However, as "part of a facade or cover-up" the students and schools were told that the photos were taken to evaluate posture.[3]

See alsoEdit


  1. Nietzsche, Friedrich, The Antichrist, 57.
  2. Ryckman, R. M., Robbins, M. A., Kaczor, L. M., & Gold, J. A. (1989). Male and female raters' stereotyping of male and female physiques. Personality and Social Psychology Bulletin, 15, 244-251.
  3. 3.0 3.1 includeonly>Rosenbaum, Ron. "The Great Ivy League Nude Posture Photo Scandal", New York Times, January 15, 1995. Retrieved on December 2, 2011.
  4. Sheldon's research led to the strong confirmation of the constitutional psychologist's expectation that there is a noteworthy continuity between the structural/physical aspects of the person and his or her functional/behavioral qualities. Although Sheldon was successful in isolating and measuring dimensions for describing physique and temperament, he cautioned that the dimensions should not be examined in isolation one by one, but, rather, the pattern of relations between the variables should be studied.
    Roeckelein, Jon E. Dictionary of Theories, Laws, and Concepts in Psychology Greenwood Publishing Group, 1998, p. 428
  5. Sheldon maintained that the person's somatotype is genetically determined and causes people to develop and express personality traits consistent with their body builds. For example, he hypothesized that endomorphs (high in fatty tissue) would be sociable, complacent, and capable of easy communication of feelings. He thought mesomorphs (high in muscle tissue) would be adventurous, bold, competitive, aggressive, and energetic, whereas ectomorphs (low in fatty and muscle tissue) would be inhibited, introverted, hypersensitive to pain, and secretive. He tested these hypotheses by having observers rate individuals on these trait dimensions and found empirical support for his ideas (Sheldon, Hartl, & McDermott, 1949, pp. 26–27). Although this study has been strongly criticized on methodological grounds (Sheldon himself made both the physical and psychological ratings), more methodologically sound studies—in which investigator bias was minimized by having one investigator rate the somatotypes and having the study participants independently rate their own personality traits—have also produced supportive evidence for Sheldon's position (Child, 1950; Cortes & Gatti, 1965; Yates & Taylor, 1978).
    Ryckman, Richard M. Theories of Personality Ninth edition, Cengage Learning, 2007, p. 260
  6. includeonly>"Nude Photos Are Sealed At Smithsonian", New York Times, January 21, 1995. Retrieved on December 1, 2011. “Later, other photographs were taken by W. H. Sheldon, a researcher who believed that there was a relationship between body shape and intelligence and other traits. Mr. Sheldon has since died, and his work has long been dismissed by most scientists as quackery. ...”


  • Hartl, Emil M.; Monnelly, Edward P.; Elderkin, Roland D. ♦ Physique and Delinquent Behavior (A Thirty-year Follow-up of William H. Sheldon’s Varieties of Delinquent Youth) ♦ Academic Press, 1982
  • Gerrig, Richard; Zimbardo, Phillip G. ♦ Psychology and Life ♦ 7th ed.

Further readingEdit

J. E. Lindsay Carter, Barbara Honeyman Heath, Somatotyping-development and Applications ( Cambridge University Press 1990)

External linksEdit

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