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Key study: Holland et al (1988)

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. Key study: Holland et al (1988). Procedure

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Key study: Holland et al (1988)

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  1. 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

  2. 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

  3. 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

  4. 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

  5. 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)

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

  7. 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?

  8. 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)

  9. 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%)

  10. 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

  11. 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

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