Homosexuality: Biological or Learned Behavior

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Homosexuality: Biological or Learned Behavior

Axia College of University of Phoenix

Homosexuality is at the front lines of the nature versus nurture debate. Many studies have been conducted, but a clear cause has yet to be found. Anti-homosexuals, consisting mainly of religious groups, believe that homosexuality is abnormal, unnatural, and can be changed. Because of their beliefs, homosexuality must be a learned behavior. Whether homosexuality is biological or learned behavior is still a mystery, but scientists are finding more evidence to suggest the former. Webster’s online dictionary defines abnormal as deviating from the normal or average. By that definition alone homosexuality is abnormal, but there are other things that are “abnormal” which are acceptable in today’s society. According to the 2000 United States Census Bureau report, 75.1 percent of Americans are Caucasian. So it is logical to assume the “average” American is Caucasian, but not being Caucasian is not considered abnormal. Minorities have genetic traits that make them different, and it is impossible to change these genetic traits. The same concept holds true for homosexuals. Homosexuals are a minority because they are biologically different from the majority. So what makes them different? Studies show there is clear a difference between the brains of homosexuals and heterosexuals, and part of it lies within the hypothalamus. The hypothalamus is a small part of the brain that controls sexual behavior, among other things, and it responds to pheromones (Hypothalamus, n.d.). Several nuclei in the hypothalamus are sexually dimorphic; this includes the interstitial nucleus of the anterior hypothalamus (INAH). The INAH is a nucleus located between the groups of tissue in the anterior hypothalamus. Although there are four INAH, only the INAH3 is widely accepted as sexually dimorphic (LeVay, 1991). Figure 1 displays the location of the hypothalamus and INAH 1-4, and a size comparison between a heterosexual male and female brain.

Figure 1. (A) Location of Hypothalamus and INAH 1-4. (B-D) Shows a size comparison of INAH 1-4 between a heterosexual male and heterosexual female. Allen et al., 1989

Heterosexual males have a larger INAH3 than heterosexual females. Simon LeVay conducted a study in which he compared the size of the INAH3 between 19 homosexual males, 16 heterosexual males, and six heterosexual females. LeVay (1991) found that homosexual males have a smaller INAH3 than heterosexual males, and their INAH3 is only slightly larger than the INAH3 of heterosexual females. The study suggests that the cause of homosexuality is located in the brain, but Anti-homosexuals do not agree with his findings. Anti-homosexuals criticize virtually every aspect of his study. They claim that LeVay was biased because of his own sexual orientation, despite him stating: I did not prove that homosexuality is genetic, or find a genetic cause for being gay. I didn't show that gay men are 'born that way,' the most common mistake people make in interpreting my work. Nor did I locate a gay center in the brain--INAH3 is less likely to be the sole gay nucleus of the brain than part of a chain of nuclei engaged in men and women's sexual behavior. My work is just a hint in that direction--a spur, I hope, to future work. (Nimmons, 1994, ¶ 4)

In their opinion the sample size was too small, and the fact 56.5 percent of the samples died of Acquired Immune Deficiency Syndrome (AIDS) related complications renders the entire study mute since the disease lowers testosterone, and there is hardly any evidence to suggest that AIDS did not create the differences in size (Chun, 2003). They also claim LeVay did not properly measure the INAH3. According to Dallas (n.d.), “His peers in the neuroscientific community cannot agree on whether the INAH3 should be measured by its size/volume or by its number of neurons” (para. 2). It is unclear if behavior can affect the brain structure or if the...
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