Key study: Holland et al (1988)

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Key study Holland et al (1988)

• Aim
• To examine if there is a higher concordance rate
  between MZ twins than DZ twins for AN
• MZ twins share 100 of genes, DZ twins 50
• If AN was genetic, there should be a higher rate
  amongst MZ twins

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Key study Holland et al (1988)

• Procedure
• Opportunity sample of 34 pairs of twins based on
  one of the pair having a diagnosis of AN
• Natural experiment (IV is naturally occurring
  genetic similarity)
• Longitudinal study
• Interview typical diagnosis for AN

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Key study Holland et al (1988)

• Findings
• Significant difference between MZ (56
  concordance) and DZ (7 concordance) twins
• Also, other psychiatric illnesses were common
  amongst non-anorexic twins

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Key study Holland et al (1988)

• Conclusions
• Suggests that AN may have a genetic influence
• The fact that the concordance was not 100 shows
  that genes are not completely responsible, they
  just provide susceptibility to the disorder
• This suggest that other influences are crucial

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Key study Holland et al (1988)

• Criticisms
• The high concordance may be due to factors other
  than genes MZ twins tend to share a more
  similar environment than DZ twins
• The look and behave similarly and are therefore
  treated alike
• No control of IV (natural experiment) therefore
  this does not control for the fact that other
  variables may be involved
• Ethnocentric (culturally biased western only)

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Key Study

• Behar et al (2001)
• Study of psychological explanations of eating
  disorders

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Behar et al (2001)

• Aims
• Effect of gender identity on eating disorders
  (ED)
• Do behavioural explanations of eating disorders
  have any evidence?
• Women may feel more pressure to be thin than men
  (idealised body image)
• Is acceptance of the feminine gender role higher
  in ED women than normal controls?

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Behar et al (2001)

• Procedure
• 126 participants (63 ED 63 controls)
• Natural experiment (ED not controlled by
  experimenter)
• Clinical interview to ensure ED
• Questionnaire to measure gender identity (BEM
  sex-role inventory)

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Behar et al (2001)

• Findings
• Significant differences in gender identity in ED
  and non-ED
• More ED were classified as feminine gender
  identity (43 compared to 23.8 controls)
• More controls were found to be androgynous (31
  compared to 19 ED)
• More controls were undifferentiated (43 compared
  to 27)

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Behar et al (2001)

• Conclusions
• Supports SLT view that ED may be due to pressures
  women face in society to look a certain way
• Shows the positive aspects of androgyny

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Behar et al (2001)

• Criticisms
• Ignores genetic, cognitive and conditioning
  factors
• Not a true experiment (no control over IV)
  causation cannot be directly attributed to the
  IV. In this case, it could mean that ED caused
  the change in gender role identity
• Ethnocentric