Human sexual behavior is extremely complex and variable; yet it is an issue that fascinates many and inspires quite a bit of scientific investigation. Probably foremost in initiating controversy and heated debate is the notion of sex partner preference, in particular, same-sex partner preferences. Given the interest this topic generates, it should be of no surprise that many scientists have focused their research energies on trying to determine what causes a given individual to develop a homosexual orientation as opposed to a heterosexual orientation. It should be pointed out that the male version of homosexuality has received the most attention from scientists, and this paper will necessarily reflect that bias.
Chief among the difficulties that such researchers face is agreeing upon a clear definition of what one means by sexual orientation. For the purposes of this manuscript, a definition offered by Gorman (1994) seems to best capture the concept: sexual orientation refers to whether one is primarily aroused by same-sex or opposite-sex stimuli, independent of the sexual behavior engaged in by that individual. Such a definition is preferred because of its focus on arousal and desire, rather than overt behavior which may be influenced by a variety of social, political, and religious pressures.
Based on the research of Kinsey and others, it is estimated that between 3 and 10 percent of the population identifies as exclusively homosexual (Kinsey, Pomeroy, & Martin, 1948; Levay, 1996; Pillard & Bailey, 1995). Many studies use some form of the Kinsey Scale to have research participants self-identify their sexual orientation. The Kinsey Scale is a seven-point scale that represents a continuum of human sexual behavior. The scores range from zero (exclusive heterosexuality) to six (exclusive homosexuality). Although Kinsey argued that there is a continuum of human sexual behavior, researchers have historically used his scale to dichotomize samples into heterosexual and homosexual/nonheterosexual groups. In response to this binary treatment, several researchers have been prompted to develop their own scales to better capture the continuous nature of human sexuality and allow for legitimate discussion of those individuals who identify as bisexual to be considered in their own right (for a more complete discussion see Klein, 1993; Rodriguez Rust, 1999).
Given prevailing social mores, we should approach the scientific literature regarding sexual orientation with some caution for a number of reasons. First, individuals willing to identify themselves as homosexual or bisexual may not be the most representative sample of their respective populations as a whole. Despite his enormous impact on the study of human sexual behavior, Kinsey received vocal criticism of the representativeness of his samples because of their willingness to participate in his studies and because of a presumed overreliance on prisoners and prostitutes (for examples see Cochran, Mosteller, & Tukey, 1954; Maslow & Sakoda, 1952), and some of these concerns continue to resonate today. Second, as previously mentioned, researchers have often imposed a dichotomy upon their samples so that individuals are grouped as either heterosexual or homosexual. This practice may not capture the true continuum of human sexual orientation and behavior and potentially confounds interpretations by treating bisexuals and homosexuals uniformly, despite research that suggests that bisexual individuals are distinct from both hetero- and homosexuals (Klein, 1993; Rodriguez Rust, 1999; Van Wyk & Geist, 1995). Finally, we should be cognizant of the motives for engaging in research focusing on the origins of sexual orientation. In reading this literature, it is clear that personal bias and opinion have colored the presentation of scientific findings and their potential implications (for a more detailed discussion see LeVay, 1996).
Researchers interested in the development of sexual orientation have often taken either a physiological or a psychosocial approach. …