What does the Sheldon typology of personality types primarily focus on?

Body build and temperament

Within psychology, the personality types given by Sheldon are fairly wellknown. Using body build and temperament as the main basis, Sheldon proposed the Endomorphic, Mesomorphic, and Ectomorphic typology. The endomorphs are fat, soft and round. By temperament they are relaxed and sociable. The mesomorphs have strong musculature, are rectangular with a strong body build. They are energetic and courageous. The ectomorphs are thin, long and fragile in body build. They are brainy, artistic and introvert.