Ways of studying

• Family studies

  • Family members share trait more frequently
  • Solyom et al showed phobias run in families
• Family studies

  Similarities between family members may actually be the result of shared environment

  Relatives learn behaviour from each other through observational learning
• Adoption studies

  Compare adopted child with biological and adoptive parents

  If child more similar to adopted nurture
• Adoption studies

  Similarities with biological parents suggest nature more important

  Plomin et al found strong correlation of IQ within biological families
• Twin studies

  MZ twins more likely share a characteristic than DZ twins implying genetic influence
• Twin studies

  Holland et al found 56% MZ concordance for anorexia

  Compare to 5% in DZ
• Twin studies

  If a trait was completely genetic the concordance rate would be 100% so behaviour is influenced by both environment