Biology of bisexuality: critique and observations.

Differentiation of human sexual orientation, particularly bisexuality, has been little studied. Most studies have lumped bisexuals with homosexuals. Those examining bisexuals separately have uniformly observed that bisexuals are often unlike either heterosexuals or homosexuals. Some authors have overgeneralized the results of animal studies as applying to humans. While animal models can provide useful hypotheses, human sexual orientation is unique. Therefore, conclusions about human sexuality based on animal research are suspect. Human sexual orientation is influenced by biological, cognitive, cultural, and subcultural variable in interaction, leading to multiple types of heterosexuals, bisexuals, and homosexuals. Understanding of human sexual orientation will improve only if these factors are accounted for in research and theory. Several studies seem to indicate that some bisexuals have a predominantly heterosexual or homosexual orientation, but high erotic responsiveness or more "masculine" characteristics, leading to versatility in sexual behavior. Early exposure to masculinizing hormones seems to predispose human females toward bisexuality rather than exclusive homosexuality.