Somatotype and constitutional psychology

Somatotype is a theory proposed in the 1940s by the American psychologist William Herbert Sheldon to categorize the human physique according to the relative contribution of three fundamental elements which he termed somatotypes, classified by him as ectomorphic, mesomorphic, and endomorphic. He created these terms borrowing from the three germ layers of embryonic development: The endoderm (which develops into the digestive tract), the mesoderm (which becomes muscle, heart, and blood vessels) and the ectoderm (which forms the skin and nervous system).

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