Bailey & Pillard

Question 1

Where can the study be used? (2)

Answer 1

Research methods used in the biological approach.
To what extent does genetic inheritance influence behavior?

Question 2

Aim

Answer 2

To investigate the role genetics may play in sexuality

Question 3

Participants

Answer 3

Researchers recruited monozygotic (MZ) and dizygotic (DZ) twins as well as adoptive brothers through gay publications
* all P were voluntary and male
* all twins were raised together - similar environment
* sexual orientation of relatives assessed by directly asking them or asking gay participant to answer

Question 4

Method

Answer 4

Researchers used questionnaires to assess the participants’ level of Childhood Gender Nonconformity (CGN)
* compared CGN between twins and adopted brothers

Question 5

Childhood gender noncomformity (+ examples)

Answer 5

A phenomenon in which pre-pubescent children do not conform to expected gender-related patterns, and/or identify with the opposite gender
* examples of forms of CGN:
* Cross-gender clothing and grooming preferences
* Playing with toys generally associated with the opposite sex
* Preference for playmates of the opposite sex
* Identification with characters of the opposite sex in stories, cartoons or films

Question 6

Results

Answer 6

The more closely genetically linked a pair is, the more likely they both are to exhibit gay or straight tendencies
* 52% of MZ twins were both self-identified homosexuals, 22% of DZ twins were so, 11% of non-related adopted brother were so
* later study showed that non-twin brothers had rate of 9.2%
* the participants’ self-reported history of childhood gender nonconformity did not predict homosexuality
* CGN does not appear to be correlated with the development of homosexuality

Question 7

Limitations (name 5)

Answer 7

• study relies on self-reported data.
• even zygosity was determined by asking the participants (a person could say that his twin was MZ, but there was no evidence provided to verify this)
• P were asked to report on their level of Childhood Gender Nonconformity: retrospective in nature (they are trying to recall what their behaviour was like as children)
  
  • memories are open to distortion, especially as the stereotype of the “gay child” may influence their perceptions of what they were like as children
• construct of homosexuality is difficult to standardize. It is difficult to know what exactly it means to be “homosexual” and whether it would be interpreted equally by all who answer the questionnaires
• small & biased sample.
• there is a limited number of MZ and DZ twins and they limited the sample to males and to those who had a gay brother
• reductionism: although genetics may play a role in our sexual orientation, does not consider EF
• not a random sample means that the study is open to ascertainment bias. As a result, the sample is not representative
• ascertainment bias: a problem in many twin studies which hope to establish a genetic link for behavior - all of the people who contacted the researchers already had a gay member of the family, skews the data

Question 8

Strengths (name 3)

Answer 8

• innovative exploration of genetic influences on sexual orientation, contributing to a shift in how homosexuality was understood
• twin study design: comparison of monozygotic (MZ), dizygotic (DZ) twins, and adoptive brothers effectively isolated genetic factors
• genetic trends demonstrated: higher concordance for homosexuality in MZ twins (52%) supported a genetic component in sexual orientation
• inclusion of adoptive siblings provided a control for environmental factors, highlighting the role of genetics
• study promoted further research on the genetic and environmental interplay in human sexuality
• findings on Childhood Gender Nonconformity (CGN) provided nuance, showing it did not predict sexual orientation