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Sex Differences

The biological process of sexual differentiation, The social process of sexual differentiation

Physical and mental differences between men and women.

The most basic question of sex differences is whether the differences between the sexes are a result of our sex chromosomes, and genetic in nature, or did humans learn them from our social and cultural environments? This argument, usually referred to as the nature-nurture controversy, is one that is common in psychological work. Most psychologists attribute our differences to a combination of nature and nurture factors. However, psychologists must be careful in their study of sex differences. After all, men and women are much more similar to each other than they are different. In the past, too, many more apparent differences—either mental or physical—between the sexes were assumed to be inherent before they were proven untrue.

There are many issues to consider when considering general differences between the men and women. The modern study of sex differences can fuel stereo-types and lead to greater misunderstanding between the sexes. Also, research is discussed in terms of statistics, which does not speak of specific people. For instance, some men may be very nurturing even though, as a group, statistics show that men tend to be less nurturing than women. Another issue is that animals, such as mice and rats and even primates, are often used to study biological sex differences, and this information does not always translate to human beings. And lastly, throughout history, psychological exploration, like many of the sciences, has focused on male subjects and male theorizing. While this work is important, there is a great deal of work yet to be accomplished in studying the psychology of women.

In the time of ancient Greece and Rome, many philosophers theorized that women were incomplete men. These theories seem to have influenced the early psychologists as well. The functional psychologists of the late 19th century, who put forth very academic studies of the sexes, made sweeping generalizations, such as women are more nurturing because they have babies. In part this information may have been true, but generalizations lead to stereotypes and stereotypes can be wrong and mistaken as truth, which can aid in developing self-fulfilling prophesies. For example, if it is widely believed, or stereotyped, that girls are not as good in math as boys, then some girls might not even try to be good at math, or teachers may not make the same effort to teach math to girls.

In the beginning of the twentieth century, psychoanalytic psychology was studying psychosexual differences and making connections between sexual organs and behaviors. By the mid-20th century, Abraham Maslow espoused a humanistic theory of personality which pointed to more similarity between the sexes than differences. By the late 20th century, psychologists and medical scientists made even greater progress in the study of the sexes through the work of sexology, endocrinology, neurophysiology, psychology, genetics, evolutionary theory, and sociobiology. Today, sex differences and similarities can be examined from many different aspects.

The biological process of sexual differentiation

There is a genetic sex differentiation at conception. Every human being starts out as 46 chromosomes arranged in 23 pairs. Twenty-two of the pairs determine hereditary characteristics, like eye color and disease potential, the 23rd pair are the sex chromosomes. This chromosome alone is completely different in males and females. If the chromosome pair is an "XX", then the embryo will be female, but if it is an "XY", it will be male. If there is a "Y" chromosome present, then the embryonic gonadal (sex glands) become a penis. If there is no "Y" chromosome present, the human embryo is automatically female. In extremely rare cases, there are embryos that have different combinations of chromosomes, which are called hermaphrodites because they are technically both sexes.

After the embryonic development of the sex glands, hormones, which are powerful chemical substances, are secreted into the blood stream and reach every cell of the embryo. These hormones form a defined reproductive tract in females and tell a male's reproductive tract not to form. The hormones also force the development of external genitalia (sex organs on the outside of the body). Finally, the hormones travel to the brain and cause differences between males and females to occur there. For example, in a female brain there are lifelong cycles or patterns of hormone release.

The social process of sexual differentiation

Biological organisms are modified once they are born. Every individual is born into an existing social context, so if it is time on the planet when females are, according to the social structure, supposed to be nurturing, then girls will be taught to be that way from a very early age. Behavior that fits that structure will be rewarded and reinforced, and behavior that goes against that norm will be discouraged. Throughout human history opposing principles have been ascribed male/female labels. The sun, for instance, has been thought of as male energy, while the more passive moon is seen as female. Mythology has reinforced human behavior, because people make up mythology. Likewise, if most literature is written by males and those males portray women in a certain way, such as being content with less political power, then the literature is reinforcing that stereotype.

Most sex differences are a combination of biological and social processes. Differences in ability, for instance, do seem to exist according to research. Men tend to be physically larger and more muscular than women, while women have proven to be constitutionally stronger, that is, less prone to certain diseases and having longer life spans. Men perform better on some cognitive tests, like visualizing 3D objects. Women tend to have greater verbal abilities. These differences are biological, but are accentuated by cultural environmental influences. Differences in achievement studies show that there is not a great difference in motivation, but motivation is activated under different conditions for males and females. These differences are socially reinforced. In looking at differences in aggression (nonaccidental behavior that causes harm), studies repeatedly show that men are more aggressive than women. This may be due to evolutionary processes. If women were busy having babies and nursing babies, then men had to go and hunt and ward off enemies, forcing men into a more aggressive role. It is possible that this information has come down genetically to modern men. Yet, studies also show that learning by example is one way that behavior evolves. If a father is physically aggressive with his family, sons tend to be that way also. In addition to evolutional and learned behaviors, there are physiological reasons, such as hormones and brain design, which can account for greater levels of aggression found in men.

There are many factors that account for our differences, and there are many similarities among us, too. In exploring sex differences, it is important to look at the questions from many angles.

Lara Lynn Lane

Further Reading

Solheim, Bruce Olav. On top of the world. Westport, CT: Greenwood Press, 2000.

Classen, Constance. The color of angels. London: Routledge, 1998.

Lips, Hilary M., and Nina Lee Colwill. The psychology of sex differences. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1978.

Christen, Yves. Trans. by Nicholas Davidson. Sex differences: modern biology and the unisex fallacy. New Brunswick, USA. and London: Transaction Publishers, 1991.

Sayers, Janet. Sexual contradictions: psychology, psychoanalysis, and feminism. London and New York: Tavistock Publications, 1986.

Wright, Elizabeth, ed. Feminism and psychoanalysis: a critical dictionary. Oxford, England and Cambridge, MA: Basil Blackwell, Ltd., 1992.

Additional topics

Psychology EncyclopediaPsychological Dictionary: Perception: early Greek theories to Zombie