Genetic and environmental influences on individual differences in attitudes toward homosexuality: An Australian twin study

Karin J.H. Verweij, Sri N. Shekar, Brendan P. Zietsch, Lindon J. Eaves, J. Michael Bailey, Dorret I. Boomsma, Nicholas G. Martin

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Previous research has shown that many heterosexuals hold negative attitudes toward homosexuals and homosexuality (homophobia). Although a great deal of research has focused on the profile of homophobic individuals, this research provides little theoretical insight into the aetiology of homophobia. To examine genetic and environmental influences on variation in attitudes toward homophobia, we analysed data from 4,688 twins who completed a questionnaire concerning sexual behaviour and attitudes, including attitudes toward homosexuality. Results show that, in accordance with literature, males have significantly more negative attitudes toward homosexuality than females and non-heterosexuals are less homophobic than heterosexuals. In contrast with some earlier findings, age had no significant effect on the homophobia scores in this study. Genetic modelling showed that variation in homophobia scores could be explained by additive genetic (36%), shared environmental (18%) and unique environmental factors (46%). However, corrections based on previous findings show that the shared environmental estimate may be almost entirely accounted for as extra additive genetic variance arising from assortative mating for homophobic attitudes. The results suggest that variation in attitudes toward homosexuality is substantially inherited, and that social environmental influences are relatively minor.

Original languageEnglish (US)
Pages (from-to)257-265
Number of pages9
JournalBehavior Genetics
Issue number3
StatePublished - May 2008


  • Attitudes
  • Genetics
  • Heritability
  • Homophobia
  • Homosexuality
  • Twin study

ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics
  • Ecology, Evolution, Behavior and Systematics


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