Gay, Straight, and the Reason Why: Chapters Ten and Eleven

gay-straight-and-the-reason-why

Based on Chapters Ten and Eleven of Gay, Straight, and the Reason Why: The Science of Sexual Orientation by Simon LeVay

Chapter Ten: The Older-Brother Effect

Gay men have more older brothers, on average, than do straight men. The reason for this is biological and not social in nature. It is theorized that the mother’s womb may build up certain factors with each male pregnancy, that predispose her sons to homosexuality.

With each older brother, the likelihood that a man will be gay is estimated to be 33 percent. This seems like a high percentage, but the rate of homosexuality among men with no older brothers is only 2 percent. Thus having one older brothers raises the likelihood of homosexuality to less than 3 percent.

The older-brother effect seem to only apply to right-handed men, according to several studies. This suggests that more than one mechanism may lead to homosexuality in men, and that they do so in a mutually antagonistic way.

Chapter Eleven: Conclusions

Sexual orientation is a part of a group of gendered traits. It results from the prenatal sexual differentiation of the brain, with the primary determinants being genes and sex hormones. Some characteristics of the bodies and minds of gay men are shifted in a female direction compared with straight men, and some traits of the bodies and minds of lesbians are shifted in a female direction compared with straight women.

One hypothesis:

Testosterone is the central hormone in determining whether the brain and body develop in a male or female fashion. If testosterone levels are high enough during a critical time before birth the brain is organized in a typically masculine manner — including a tendency to be attracted to women. If levels are low, the brain organizes in a female manner.

The estimated heritability of homosexuality ranges around 30-50 percent; similar to estimates for many other psychological traits. Few major genes have been identified that could be responsible for influencing homosexuality. It is likely that, like most heritable psychological traits, sexual orientation is influenced by multiple genes, each contributing a small effect. Mutual inhibition functions between brain centers that contribute to sexual orientation as shown by the occasional change in sexual orientation that results from brain damage or reduction of hormones.

Does the idea that sexual orientation is linked to gendered traits stigmatize gay people by reinforcing stereotypes? This is debatable, but the findings that gay and straight people tend to differ in gender-related traits is a valuable insight for understanding the origins of sexual orientation. The blend of gender-variant and gender-typical traits of gay people is what enables them to make their unique contributions to society. Acknowledging this should foster acceptance of gay people as they are, instead of encouraging them conform with straight majority.

See also:

Gay, Straight, and the Reason Why Series:

Gay, Straight, and the Reason Why: Chapters Eight and Nine

gay-straight-and-the-reason-why

Based on Chapters Eight and Nine of Gay, Straight, and the Reason Why: The Science of Sexual Orientation by Simon LeVay

Chapter Eight: The Brain

All mental characteristics have some representation in the brain; sexual orientation should be no different. As mentioned in the Introduction, a region in the brain known to regulate male-typical sexual behavior –INAH3– was reported to be significantly smaller in gay men than in straight men. Other regions of the brain have been found to differ between gay and straight people.

A study was done on the brains of lesbians and straight women. The study found that lesbians had significantly less gray matter than straight women, especially in a site known to control processes that differ between men and women. In another study, gay men in a sample were found to have female-typical brain volumes and connections, while lesbians were found to have male-typical volumes and connections. The connections were found  in the brain region known as the amygdala which, among other functions, controls processing of emotion and is involved in regulation of sexual functions.

Observations on human and non-human subjects suggest that male heterosexuality is not simply an attraction to the opposite sex, but active suppression of attraction to the same sex. Damage to or removal of the analogous region of INAH3 in male rats causes a change in their usual preference for female sex partners, to a preference for male partners. Homosexual attraction and/or behavior can occur in previously heterosexual men with Klüver-Bucy syndrome, caused by damage to the amygdala; the major source of input to INAH3 and nearby brain regions involved in sexuality. In addition, homosexual attraction can appear in a minority of men who are castrated for prostate cancer. These changes suggest that there are biological mechanisms for setting up sexual attraction to one sex that depends primarily on preventing attraction to the other sex.

Continue reading

Gay, Straight, and the Reason Why: Chapters Six and Seven

gay-straight-and-the-reason-why

Based on Chapters Six and Seven of Gay, Straight, and the Reason Why: The Science of Sexual Orientation by Simon LeVay

Chapter Six: The Role of Sex Hormones

There are no consistent differences in testosterone levels between gay and straight men, according to many studies. In contrast, up to one-third of lesbians (self-identified “butch”) may have higher testosterone levels in comparison to straight women. Markers of prenatal hormonal levels shows some differences that line up with sexual orientation.

Congenital Adrenal Hyperplasia (CAH) is a condition where a fetus is exposed to extremely high levels of male sex hormones. Women affected by CAH have been shown to be more masculine in mental and behavioral traits. Since homosexuality is linked to a variety of gender-atypical traits, it is unsurprising that studies have found CAH women to also be more homosexual, on average, than women not affected by CAH.

A similar, but opposite condition is androgen insensitivity syndrome (AIS), where the molecules that sense the presence of testosterone and other male hormones functions poorly or not at all. Genetic males with this condition grow up to look like women, identify as women, and most importantly, the majority of individuals with AIS are sexually attracted to men. This is consistent with the theory that sex hormones are a key determining factor in development of sexual orientation.

In genetically healthy individuals, similar findings have been presented. Sense of hearing differs between men and women and is affected by the greater prenatal exposure of men to testosterone and other male hormones. In studies, gay men have shown more female-like responses to sound and lesbians have shown more male-like responses. These findings are consistent with sexual orientation as an aspect of gendered traits.

Continue reading

Gay, Straight, and the Reason Why: Chapters Four and Five

gay-straight-and-the-reason-why

Based on Chapters Four and Five of Gay, Straight, and the Reason Why: The Science of Sexual Orientation by Simon LeVay

Chapter Four: Childhood

Boys and girls show fairly consistent differences in mental and behavioral traits; these traits are called “gendered traits”. Some of these differences arise through socialization, but many arise through biological factors such as hormone levels. Studies have shown that children who become gay adults (“pre-gay” children) are more likely to be gender-nonconformist, i.e. show characteristics typical of the opposite gender.

Two main types of methods are used to understand the characteristics of “pre-gay” children in comparison to “pre-straight” children:

  1. Retrospective Studies

The most widely used method. In retrospective studies, adults give descriptions of what they were like as children. Using this method, researchers have found that pre-gay boys are less physically aggressive than pre-straight boys and are more likely to take part in traditionally female activities. Overall, both pre-gay boys and girls were more likely to be gender-nonconformist, but for boys, such traits were much more predictive of adult homosexuality.

2.    Prospective Studies

A method where two groups of children –a control and a particularly gender-nonconformist group– are studied up to adulthood. These studies have made similar findings; noticeable femininity in boys is a predictor of adult homosexuality. Masculine traits in girls is not particularly a predictor of lesbianism — most girls who show traditionally male traits (“tomboys”) grow into heterosexual women.

Overall, these studies suggest that homosexuality is a part of a “package” of gender-atypical traits while heterosexuality is part of a set of gender-typical traits.

Chapter Five: Characteristics of Gay and Straight Adults

Studies on adults have found that mental and behavioral traits of gay men and women is shifted towards the opposite gender, but not completely opposite. Gay men show more of a gender shift than lesbians, who show no shift at all for some gendered traits.

Women tend to be more verbally fluent than men and better at tasks involving memory. Gay men score similarly to women on tests of verbal fluency and memory, while lesbians score similarly to men on such tests. Gay men and women are similar to their straight counterparts in aspects of sexuality, except in the roles preferred in sexual encounters. Some gay men are more receptive and some lesbians (so-called “butch” lesbians) are more dominant. Gay men strongly prefer more masculine partners and lesbians mildly prefer more feminine partners.

See also:

Gay, Straight, and the Reason Why Series:

Gay, Straight, and the Reason Why: Chapters Two and Three

gay-straight-and-the-reason-why

Based on Chapters Two and Three of Gay, Straight, and the Reason Why: The Science of Sexual Orientation by Simon LeVay

Chapter Two – Why We Need Biology

The primary nonbiological theories for the origin of sexual orientation have encouraged the search for biological explanations. As a whole, these theories and their weaknesses make clear the need for biology in understanding sexual orientation and homosexuality.

  • Psychoanalytic Theories (pioneered by Sigmund Freud)

A. In males, the erotic instinct, also called the libido, is directed towards other males early on in life. This libido is later usually transferred to the mother in the infamous “oedipal stage.” In pre-oedipal homosexuality this transfer process doesn’t occur or is interrupted, causing lifetime homosexuality.

B. In oedipal  homosexuality, a young male is frustrated by his inability to be with the mother that he is so attracted to. He resolves this frustration by identifying with her and seeking male partners that remind him of himself.

C. In females, the young female suffers from an unresolved oedipal complex that has been redirected towards her father. She falls in love with women who represent the mother she has grown to love and hate.

The problem with these theories: There is no evidence, and the complexity and improbability of them count against their being true.

  • Learning Theories (Early Sexual Experiences)

A. A person’s first sexual contact determines their orientation. If their first contact is with a woman, then they will desire women, if with a man, they will be attracted to men.

The problem: Most people are aware of their sexual orientation as virgins. Also, young men in some non-Western cultures and single-sex boarding schools where sexual contact with other boys is common are no more likely to become homosexual adults.

B. Children who are molested are turned off the sex of their molester; e.g. girls who are molested by men become lesbians.

The problem: Since almost one-third of women will have an experience fitting a broad definition of sexual abuse, yet much less than one-third of women are lesbians, this theory is not likely true. Also, studies have found that lesbians are no more likely than straight women to have been abused as children.

  • Learning Theories (Gender Learning)

Children, after becoming aware of their gender, learn their sexual orientation from imitation of parents or others in their social environment.

The problem: Children who are reared as the opposite gender due to tragedies during infancy (e.g. males who lose their penis due to disorder or surgery) do not accept this gender. They are attracted to others of their assigned  gender and in most cases, revert back to their original gender.

Chapter Three – Outline of a Theory

The basic pathway that controls the development of sexual orientation (and other traits concerning gender) in nonhuman animals:

  1. Differences in sex hormone levels during development cause the brain to organize in a more male or female-like manner. These hormone levels are also modified by random variability, genetic differences, and environmental factors.
  2. Early sex hormone levels and the resulting differences in brain development influence preference for male and/or female partners later on in life.

This pathway appears to be the same route by which humans develop sexual orientation.

See also:

Gay, Straight, and the Reason Why Series:

Gay, Straight, and the Reason Why: Introduction and Chapter One

gay-straight-and-the-reason-why

Note: I am currently reading a nonfiction piece by neuroscientist Simon LeVay entitled Gay, Straight, and the Reason Why: The Science of Sexual Orientation. For the next few weeks, at the beginning of each week, I’ll be publishing a summary of a chapter or two of the book.

Introduction

Simon LeVay, a British-American and openly gay neuroscientist gained media attention in the early ’90s when he published a groundbreaking paper in the journal Science. The article, entitled “A difference in hypothalamic structure between heterosexual and homosexual men”, detailed his study on the brains of late humans which found that a region in the brain known to regulate sexual behavior was considerably smaller on average in gay men than in heterosexual men. This paper and similar papers of the time inspired new biological research into the contentious question: Why are gay people gay?

In Gay, Straight, and the Reason WhyLeVay outlines the research that has taken place since then and lays the foundation of a credible theory for the biological origins of sexual orientation via gender.

Chapter One – What is Sexual Orientation?

Sexual orientation is usually judged on the basis of a person’s sexual attraction to others — opposite sex attraction means heterosexuality, same sex attraction is known as  homosexuality, sexual attraction to both sexes equals bisexuality. Sexual orientation, contrary to belief, has little to nothing to do with sexual behavior, i.e. the extent to which a person has sexual contact with men or women. Sexual behavior is influenced by a variety of factors which are not a part of actual attraction, such as availability of sexual partners and a person’s sense of morality. Sexual attraction itself can be divided into two parts — physical attraction; the desire to engage in sexual contact, and romantic/emotional attraction; the desire for non-sexual psychological union.

Sexual orientation in men and women is generally stable throughout life, but moreso for men than for women. Some women but few men have true changes in sexual orientation later on in life.

Heterosexuality is far and away the most common sexual orientation for both men and women. How many people in the world are non-heterosexual (homosexual or bisexual)? Most surveys across the globe have resulted in similar numbers — about 3.5 percent of men and 1.5-2 percent of women in the world have attraction to persons of the same sex. Non-heterosexual men are mostly homosexual, while non-heterosexuality in women is divided close to evenly between homosexual and bisexual.

Gay and bisexual people have existed across time periods and cultures. Studies in large cities in non-Western countries such as the Philippines and Guatemala have shown that gay men exist in around the same numbers as those that live in large Western capitals. Ancient Greek writings suggest that the sexual attraction of some men and women for those of their gender was well-known and tolerated. This evidence suggests that homosexuality has a biological rather than social origin.

See also:

Gay, Straight, and the Reason Why Series: