The Psychology of Everyday Life:Love, Marriage, and the Baby Carriage

Sexual Orientation

What are other biological theories of homosexuality?

There is also some evidence of subtle brain differences between homosexual and heterosexual men. In 1991, Simon LeVay published work suggesting that a certain part of the hypothalamus, the region of the brain that controls hormone function, may be smaller in homosexual men than in heterosexual men. His study has been criticized however, because many of his homosexual subjects were HIV positive. The genetic component of homosexuality has also been explored, largely through twin studies. The correspondence in sexual orientation between identical and fraternal twins gives information as to the genetic heritability of sexual orientation. If identical twins are more similar in their sexual orientation than fraternal twins, this suggests that genetics play an important role (because identical twins share 100 percent of their genes while fraternal twins share only 50 percent). The evidence for this has been mixed. Some studies show a strong genetic influence while others do not. It is possible that the genetic influence is most powerful in people who are strongly, if not exclusively, homosexual. Genetics may be less important in people with milder homosexual tendencies.


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