Thinking & Sex: It's Not Just Guys

For a female Proboscis Monkey, a male with a big nose is a male with a big sex appeal. A male cockroach will only mate with a female if she smells just right. And only a male Hanging Fly could make an insect corpse look appetizing to a female. Humans, like their less-developed animal counterparts, have criteria for a good mate as well. There are many areas of psychology that explain why sex is very important to both men and women, such as Freud's psychoanalytical theories of personality, evolutionary approaches to mate selection, and areas of biological health psychology.

Freud had many theories regarding development of personality, and many of his theories revolved around sex and sexual development. He believed people have three parts of their consciousness: the Id, Ego and Superego. The Id is present at birth and is responsible for desires. The Ego satisfies the Id by keeping reality in mind and the Superego is a person's moral compass. Freud theorized that we are driven by two forces, the Death instinct and the Life instinct, known commonly today as the Libido. The combination of the Libido and Id is what creates sexual desires.

In addition to the Id and Libido, Freud believed people go through stages during which the Id's energy focuses on different parts of the body. These bodily regions are called erogenous zones, which are oral, anal, phallic and genital. If a person has an unresolved conflict while in one of the stages, it will manifest into a fixation later in life. To feel resolution, people indulge these fixations. For instance, if a teenage girl's mother constantly yells at her because of her boyfriends, she will develop a genital fixation. To resolve her genital fixation, she may choose to participate in casual sex with many partners, just to satisfy her Id's fixated demands.

According to evolutionary and biological psychology, other areas make sexual demands. When it comes to choosing a mate, men and women have different criteria. Women look for men who are symmetrical with big, square jaws. There are more than just physical characteristics that women look for in a man. Females tend to prefer older men with a secure financial status and high social standing. Robert Trivers's theory of Parental Investment. Women must invest at least nine months in order to create a child. Once the child is born, mothers spend years raising the child. Thus, a woman's reproductive success is maximized by finding a partner who will invest his time and resources in raising her offspring. Men, however, are required to do nothing after the act of copulation. Young men with few resources cannot contribute the long-term financial stability that an older, more established man can.

There is another side to Trivers's Parental Investment Theory. A man looks for women who can easily bear his children. His reproductive success is maximized by having sex with many young, healthy women. Signs of health that men look for are a high forehead, full lips, short jaws, small chins and a favorable waist-hip ratio. A small waist and large hips are favorable for childbearing and suggest reproductive health. Men's criteria for a favorable reproductive partner tend to be more physical than women's.

While evolutionary psychology gives answers for the question who, biological health psychology gives answers for the what, why and how of sex. What happens during sex? Even though men and women vary in many ways, the physiology of sexual intercourse is very similar. Males and females experience the same phases: excitement, plateau, orgasm, and resolution. During the excitement phase, vasocongestion, the enlarging of blood vessels, occurs. Vasocongestion is accompanied by substantial increases in blood pressure, heart rate, muscle tension and respiration rate. The plateau phase is characterized by continuing arousal, but at a slower rate. Ideally, orgasm follows the plateau phase. Orgasm is the pinnacle of sexual arousal, which produces muscle contractions throughout the pelvic region, increased heart and respiration rate and blood pressure. Resolution quickly follows orgasm. During resolution, there is a decrease in blood pressure, heart rate, muscle tension and respiration rate.

Why do people have sex? Physiologically, sex is much like a good aerobic work-out, providing much of the same benefits. Endorphins are released, attitude is improved, stress is reduced, and self-concept is heighten. Of course, there is the obvious reason: to procreate.

How can biology and psychology explain sexual dysfunction? For a long time, sexual dysfunction was thought to be purely biological. Today, research is finding that there are increasing psychological factors. Some factors include, but are not limited to, psychosocial pressures, such as religious guilt, pressure to perform and obedience (or disobedience) of what are frequently culture-specific sexual taboos.

Female crocodiles find a mate attractive if he blows bubbles in the water under her belly. Male and female humans have different criteria for mate selection. The criteria is not only different from the rest of the animal kingdom, it is different from gender to gender. The reasons for sex are also different from many animals in the world. Humans are one of only a few species that engage in sexual intercourse for the fun of it. Psychology, a science unique to humans, can explain the differences. Many areas of psychology give reasons to explain the importance of sex to both men and women. Some of these areas include Freud's psychoanalytical personality theories, evolutionary ideas about mate selection sexual motivation, and parts of biological health psychology.