Heston AO3

• Sample - matching to controls (+)

  > 47 participants born to schizophrenic mothers were carefully matched with a control group on sex, type of eventual placement and length of time in childcare

  > Therefore, Heston could be more confident that having a schizophrenic mother was the only difference affecting the participants and controls
• Sample - generalisability (-)

  > Sample of schizophrenic mothers may be unrepresentative of all schizophrenic mothers as these mothers gave their babies up for adoption as they were in a psychiatric unit

  > Therefore, the results cannot be generalized to schizophrenic mothers who didn't give their children up for adoption, lowering population validity
• Procedure - data collection (+)

  > Data was collected from several different sources including interviews, school records and personality tests

  > Led to detailed quantitative and qualitative data from several sources allowed psychiatrists to collect detailed data to make an informed diagnosis of schizophrenic, increasing validity
• Procedure - selective placement (-)

  > Adopted children are often placed with families similar to their birth family

  > Heston may have over estimated the role of genes in their contribution towards the development of schizophrenia, as the similar environments means there could be aspects of the environment which contribute to the development
• Concluding strength - ethics (+)

  > Hestons procedure was that the adoptions occurred naturally and it did not involve any direct manipulation of the children's placement

  > The study may be viewed as an ethical way of measuring the genetic basis of schizophrenia