While there is a vast psychosocial
literature on human sexuality, little serious biological research has been
done on the aetiology of human sexual orientation. In view of the current
AIDS epidemic, this is of some interest. We have obtained a grant from the US
National Institute of Mental Health to investigate sexuality and sexual
attitudes in volunteers twins from the Australian NH&MRC Twin Registry.
Twin pairs' responses remain anonymous. Completed questionnaires have been
received from over 1800 male and 3000 female twins. Preliminary analysis
suggests a modest genetic contribution to male, but not female declared
homosexuality. However, much larger genetic contributions are estimated for a
latent variable indicated by thoughts of same-sex orientation, and measures
of childhood and adult gender conconformity.
All members of the Alcohol Cohort 1 and Alcohol
Cohort 2 studies were sent a consent letter asking whether or not they
would participate in a sex-related questionnaire. They were asked to return
the bottom part of the consent letter with their reply.
All those twins who answered
"yes" were then sent a questionnaire and a consent form in the same
package. The consent form had a label with the twin's demographic details and
ID but the questionnaire had no identifying information. Twins were asked to
return both the questionnaire and the signed consent form but in separate
envelopes. In this way we could not match questionnaires to individual twins
but the returned consent forms acted as a good proxy for return of
questionnaire.
Each questionnaire had space at the top
for a 10 digit number. The twins were asked to consult with each other and
agree on a 10 digit number which they would then each enter on the top of
their questionnaires. In this way, questionnaires could not be related to
individual twins but twin pairs could be matched up.
The questionnaire contained sections on:
- Background Questions
- Childhood and Adolescent Behaviour
- Your Present Personality
- Sexual Feelings and Behavior
- Family Information
- Handedness
- Your Feelings about the Questionnaire
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