Twin Studies

Mind map descrbing and showing strengths and weaknesses of twin studies

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  • Twin Studies
    • Describe
      • Focuses on CONCORDANCE RATES of twins with respect to disorder.
      • MZ twins compared with DZ twins
      • MZ twins have greater genetic similarity
        • Both types grow up in identical environments
      • If MZ CONCORDANCE is higher than DZ CONCORDANCE, a genetic component sugested
    • Strengths
      • Perfect control for genetic inheritance studies
        • MZ twins share 100% DNA. DZ twins share 50% DNA
        • Effect of nature vs. nurture can be studied effectively
          • IV already manipulated
      • More multiple births taking place
        • Replicate findings of twin studies with other sample of other cultures
          • Increase reliability and generalisability
      • Usually nothing is manipulated only measured
        • Also usually takes place in a natural setting
          • Studies usually ethical and valid
    • Weaknesses
      • Twins not always exposed to same environmental influencese
        • MZ twins are more likely to be treated the same than DZ twins
          • E.g MZ twins more likely to be dressed the same than DZ twins
          • Lack of validity
      • Difficulty in getting a large sample
        • Difficult to get twins with exact requirements
          • E.g hard to find willing twins where only one suffers from szhizophrenia
          • Reduced generlisability
      • Twin studies are often case study style
        • Lack of generalisability
    • Key Terms
      • Concordance Rates
        • The probability of one twin having the disorder if the other already has it. Expressed as a percentage


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