Wednesday, January 12, 2011

Does male/female hormonal differences influence behaviors and attitudes?

It's time to root out the imposition of gendered behavior stereotypes from all aspects of our lives. Ending gender oppression means encouraging our children to experiment with alternative gender expressions...
- Nancy Nangeroni, a transsexual activist quoted in Transgender Warriors

It is fundamental that individuals have the right to define, and to redefine as their lives unfold, their own gender identity, without regard to chromosomal sex, genitalia, assigned birth sex, or initial gender role.
- From The International Bill of Gender Rights, approved by the International Conference on Transgender Law and Employment Policy, 1993


Are men and women different? They're different anatomically, of course, but are they different in any other ways? Do their hormonal differences influence their behaviors and attitudes? Do they process information differently?

Feminists and gay theorists often say "no" to these questions. They maintain that the differences between men and women are mostly the result of socialization in male-dominated societies, and that it is patriarchal oppression that has relegated women to feminine gender roles. Biology is said to have little to do with abilities or sex roles in our society. Some feminist writers actually believe that the idea of "two sexes" (male and female) is a myth. Dr. Anne Fausto- Sterling, writing in "The Five Sexes: Why Male and Female Are Not Enough," says that western culture is defying nature by maintaining a "two-party sexual system," for "biologically speaking, there are many gradations running from female to male; and depending on how one calls the shots, one can argue that along the spectrum lie at least five sexes--and perhaps even more."

Professor Steven Goldberg, Chairman of the Department of Sociology at City College of New York, has written a book with the provocative title, Why Men Rule--A Theory of Male Dominance. In the book, he debunks much of the feminist mythology surrounding the issue of differences between males and females.  Goldberg maintains that although males and females are different in their genetic and hormonally-driven behavior, this does not mean that one sex is superior or inferior to another. Each gender has different strengths and weaknesses. However, he believes the neuro-endocrinological evidence is clear: The high level of testosterone in males drives them toward dominance in the world, while the lack of high levels of this hormone in women creates a natural, biological push in the direction of less dominant and more nurturing roles in society.

 It is true, that when investigations about male/female brain differences began, many scientists were also skeptical about the role of genes and of biological differences, because cultural learning is very powerful and influential among humans. Are girls more prone to play with dolls and cooperate among themselves than boys, because they are taught to be so by parents, teachers and social peers, or is it the reverse order?

But now, after many careful controlled studies where environment and social learning were ruled out, scientists learned that there may exist a great deal of neurophysiologic and anatomical differences between the brains of males and females.

Role of evolution

According to the Society for Neuroscience, the largest professional organization in this area, evolution is what gives sense to these gender differences. "In ancient times, each sex had a very defined role that helped ensure the survival of the species. Cave men hunted. Cave women gathered food near the home and cared for the children. Brain areas may have been sharpened to enable each sex to carry out their jobs".

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The advantage of women regarding verbal skills also makes evolutionary sense. While men have the bodily strength to compete with other men, women use language to gain social advantage, such as by argumentation and persuasion.

Interestingly, when we deliberately change sex-role behavior -- say, men become more nurturing or women more aggressive -- our hormones and even our brains respond by changing, too.

What are hormones?

The definition of a hormone is a chemical substance produced by an endocrine gland that has a specific effect on the activities of other organs in the body. The major female and male hormones can be classified as estrogens or androgens. Both classes of male and female hormones are present in both males and females alike, but in vastly different amounts. Most men produce 6-8 mg of the male hormone testosterone (an androgen) per day, compared to most women who produce 0.5 mg daily. Female hormones, estrogens, are also present in both sexes, but in larger amounts for women. Estrogens are the sex hormones produced primarily by a female's ovaries that stimulate the growth of a girl's sex organs, as well as her breasts and pubic hair, known as secondary sex characteristics. Estrogens also regulate the functioning of the menstrual cycle.

Role of hormones

Sex hormones play a significant role in developing a male or female differentiated brain. This lies in the mother’s hormone levels during pregnancy. Studies in lab animals have proved that altering hormone levels during pregnancy can produce brains with male or female traits depending on the type of hormone added to the pregnant female.

For instance, if testes of newborn male rats are removed, they tend to develop thicker left hemispheres than rats whose testes are still intact. This is a female trait. If a pregnant female monkey is injected with testosterone, the offspring will show one or more male traits. These traits are known as the five characteristics of the male-differentiated brain: aggression, competition, self-assertion, self-confidence, and self-reliance.

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These characteristics are related to levels of testosterone whether in males or females. Men who act as if they have female differentiated brains, in fact have lower levels of testosterone, and women who behave with male differentiated brains possess higher levels of testosterone than normal. The male differentiated brain tends to be one that is aggressive, spatial, and math proficient. The female differentiated brain is one in which is nurturing, and verbose.

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There can be a relationship between body asymmetry and gender behavior. The amount of androgens and estrogens in the body can affect both gender behavior and body asymmetry. These hormones are passed from mother to newborn during the embryonic stage of life.

For example: if a female embryo receives an excess of androgen during pregnancy, she is likely to have a male appearance, behavior and male differentiated brain. On the other hand, if a male embryo receives an excess of estrogen. Male appearance, and behavior is prevalent, but with a female differentiated brain. When a female embryo is subjected to a large amount of estrogen, she has an excessive female appearance and behavior. The same is true for males when they receive large amounts of androgen during pregnancy. They tend to be a super male with lots of hair and very aggressive.

Various events can cause this to happen during pregnancy. The unborn child can be subjected to various hormones during crucial periods during pregnancy. Mutations in the chromosomal matter may cause one of the events to occur. Major or sustained stress levels will suppress testosterone levels; renal dysfunction will produce too much testosterone. Injections for diabetes will cause an increase in estrogen, barbiturates, and exercise. Spurt exercise will cause an increase in testosterone, while sustained exercise like a long run or jogging will lower the amount. While the brain is immersed in hormones during pregnancy, the true affect does not appear until puberty begins and the brain becomes activated due to the full immersion of the hormones in the body.

Scientific Evidence

(1)     Girls who were exposed to high levels of testosterone because their pregnant mothers had congenital adrenal hyperplasia seem to have better spatial awareness than other girls and are more likely to show turbulent and aggressive behavior as kids, very similar to boys'.
(2)      There was a time when women were prescribed a synthetic female hormone (diethylstilbestrol), in an attempt to prevent repeated spontaneous miscarriages. Boys born to such women are likely to show more female-typical, empathizing behaviors, such as caring for dolls.
(3)      Male babies born with IHH (idiopathic hypogonadotrophic hypogonadism) have very small testes (and therefore low levels of testosterone) and they are worse at spatial aspects of systemizing, relative to normal males.
(4)      Other male babies born with androgen insensitivity (AI) syndrome (testosterone is an androgen) are also worse at systemizing.

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Review the empathizing – systemizing (E-S) theory in more details on our previous post: http://menopause-aid.blogspot.com/2011/01/behavioral-differences-between-men-and.html

Interestingly, the brain areas that were found to differ between men and women are ones that in animals contain the highest number of sex hormone receptors during development.

After all, males and females differ only by one Y chromosome, but this makes a real impact upon the way we think, feel, behave and react to so many things.


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