Medicine & USMLE

Biological Theory of Personality

  1. Trait Personality Theory and Five-Factor Model
  2. Social Cognitive Theory of Personality
  3. Biological Theory of Personality
  4. Humanistic Personality Theory
  5. Behaviorist Personality Theory
  6. Psychoanalytic Personality Theory


The Biological Theory of Personality asserts that your genes help determine your personality. Genes help shape the structure of the brain, and neural structure in turn mediates personality. This theory focuses on the role of nature in the nature versus nurture debate. 

Key Points

  • Biological Theory of Personality
    • Personality is encoded in genes/DNA
      • Genetic expression determines brain structure/function, which manifests as personality.
      • Personality is therefore heritable
        • Identical twins should have similar personalities (same genetic code)


Identical twins have identical genetic codes. According to Biological Theory of personality, even identical twins raised in different environments should share some similarities in their personalities. This is because their identical genes led to at least some similarities in the neural structures of their brains, and those similarities in their neural structures mediate similarities in their personalities.