Studies

• Twin Studies

  • Study gene influence
  • Nature/nurture
  • Examine concordance rates of MZ (100% genes) and DZ twins (50%)
  • High concordance rate between just MZ suggests a genetic cause
  • Similar rate between both suggests environment as cause
  • Strengths:
  • Generated large data volume
  • Provide a very useful way of studying gene influence
  • Weaknesses:
  • Recruitment:
  • Advertisements; biased, unrepresentative, most twins do not participate
  • Twin fest, US, (those celebrating similarity are likely more similar than average)
  • Most people aren’t twins
  • Unrepresentative of non-twins
  • Ungeneralisable
• Adoption Studies

  • Compare
  • MZ twins, different upbringing, psychological traits
  • Children's traits with adoptive and biological parents
  • Strengths:
  • Offers direct comparison, nature vs nurture
  • Can investigate wide variable range with varied samples and methods, e.g. trans-racial adoptions or meta-analyses
  • Weaknesses:
  • Adoptees often share similar environment as bio families (adopted in 30-mile radius)
  • Agencies try for similar to bio families for similar developmental experiences
  • MZ twins apart minimal, small sample
  • Difficult to get large and diverse sample, limiting generalisability