gottesman and shields - twin study

• example twin study

  gottesman & shields (1966)
• gottesman and shields - 1) what was the sample?

  57 participants from maudsley and bethlem royal joint hospital using opportunity sample, assessed against their twin for the inheritance of SZ
• gottesman and shields - 2) what were twins assessed for?

  zygosity to check whether they were MZ or DZ e.g: blood grouping
• gottesman and shields - 3) what was used to determine the presence of a mental disorder

  qualitative and quantitative methods e.g: MMPI personality tests, hospital case records and semi-structured interviews
• gottesman and shields - what were the findings?

  there was a higher concordance rate where both twins had SZ for MZ twins (42%) compared to DZ twins (9%)
• strength of gottesman & shields

  • high internal validity
  • study used same measures of SZ e.g: MMPI tests - means study can easily be replicated to see if findings would still be the same today
  • conclusions made about whether each twins had SZ should be more reliable
• weakness

  • concordance rate of SZ was not 100%
  • MZ twins had a concordance rate of 42%
  • therefore, study unable to provide conclusive evidence of genetic influence on SZ or other human behaviours
• weakness

  • whilst twins share same genetic information, difficult to separate environmental factors
  • e.g: from before the study took place
  • studies cannot establish genetics as a causational factor for behaviour
• aim - to investigate if SZ had a genetic basis