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4.1: Sexual Function and Behavior

Difficulty Level: At Grade Created by: CK-12
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How does the body respond to sexual arousal and what are some normal sexual behaviors among humans?

Why are people interested in sex? Unlike food, sex is not essential to keep us alive as individuals (it is necessary to keep us alive as a species). So why do some people act as if they are sexually hungry?

“Sexuality is a taboo subject.”

-7th grader

In the past, scientists described sexual hunger as a sexual instinct. It was thought that this was a natural urge that somehow pushed people into sexual activity. But no one could tell where this instinct came from or how it worked. Currently, the term sexual drive is used to mean something similar, but less mysterious. A drive motivates or directs an individual toward a specific goal-it increases the chances that a person will behave a certain way. Thus, the sexual drive pushes or pulls us to become sexually interested and seek sexual fulfillment.

The ability to become sexually aroused is already present in childhood. But the intensity, or the strength, of the sexual drive increases at puberty, which is why we talk about the awakening of sexual interest during adolescence. Moreover, sex can now result in pregnancy because of the maturation of the reproductive system.

Why does the sexual drive increase in puberty? Some scientists believe that an increase in the level of sex hormones, especially testosterone, in both boys and girls, causes stronger sexual urges.

Much of what we know about the effects of hormones on sexual behavior is based on studies with animals. If you have observed animals on a farm or pets at home, you already may know that sexual activity happens only at certain times with those animals-when the female animal is in heat. During this time, the male animal is attracted to the female and she will respond to him. This period of sexual attractiveness and responsiveness in the female animal is called estrus. It coincides with ovulation, or the release of an egg from the ovary (gland producing female eggs and hormones), and is caused by the increased levels of female sex hormones. This is not just coincidence. The basic purpose of sex among animals is to produce young, which is called reproduction. Timing the increase in sexual drive with ovulation increases the chances of pregnancy.

Did You Know?

Some organisms reproduce sexually and others asexually. Sexual reproduction involves the fertilization of female eggs by male sperm. This fertilization can occur internally (as with humans) or externally (as with fishes). Sexual reproduction allows for genetic diversity-combining the characteristics of the male and female into a new individual. Asexual reproduction requires only one of the species-it makes many identical copies of itself (as with bacteria). Although this form of reproduction is simpler and faster, it does not allow for any genetic differences or ways to adapt to changing environments.

Some of you may have pets whose gonads-ovaries or testes-have been removed by a veterinarian to prevent reproduction (referred to as being fixed, neutered, or spayed). Removing the gonads of an animal not only makes pregnancy impossible, but it also turns off the sexual drive by removing the sources of sex hormones.

What do we know about humans? Is our sexual drive and behavior similarly controlled by hormones? Hormones influence our sexual drive, but human sexual behavior is much more complex. For one thing, human sexual behavior is not a function of the female being in estrus. Though she goes through the ovarian cycle, the human female is not limited to a period of increased sexual interest during ovulation. Sexually mature girls and women may be sexually aroused at any time of the month. The sexual interest of the human male is not in response to any particular phase of the female cycle but also may occur at any time.

Causation Think of 3 events in your life, or historically, that show direct causation (cause and effect). Then think of 3 events that show correlation, but not causation.

You will note in Figure 3.1 that the sharp increase in the level of testosterone during puberty is accompanied by the onset of sexual activities, as well as of falling in love and dating. Based on this evidence, it would be correct to say that in boys, rising testosterone levels are correlated with the onset of sexual and romantic interest. Correlation means that two events tend to occur together. This is not the same as causation, or saying that one event is the cause of another event. Furthermore, the relationship between the events shown in Figure 3.1 and hormones may vary. For example, the onset of nocturnal emissions (discussed later in this unit) is a direct result of puberty, which in turn is brought about by hormones. Masturbation may occur before puberty, but it is more common during and following puberty. Therefore masturbation may be linked to hormones.

Figure 3.1 Testosterone levels and sexual and romantic experiences at puberty in boys.

Human sexual behavior is greatly influenced by our intimate relationships and our feelings for one another. How we behave sexually is determined not only by hormones but also by how we feel and think about sex. Our upbringing and our community largely shape our feelings and thoughts about sex. Therefore, a boy or girl may start dating at a particularly young age because others are doing it, no matter what their level of biological development or level of hormones. Moreover, human beings are concerned not only about how they want to behave, but also about how they should behave sexually, which may mean sometimes not doing what they want to do. We will discuss these moral considerations concerning sex later in this unit.

“Sometimes it's scary to have strong feelings and not know what to do with them.”

-7th grader

Some parents freely discuss sexual topics with their children. Others do not. Parents may sometimes see their child touching his or her genitals and say, “That's not nice” or “Don't do that,” without explaining why. Or if a child asks, “How did Mommy get pregnant,” he or she may be told, “Mommy and Daddy were in love.” The child is left no wiser about reproduction. In other cases, a child is given a wrong reason such as, “If you don't stop playing with your penis, you will get germs.” Such attitudes leave children confused or may make them feel like there must be something wrong about sex.

Even when parents are willing to talk about sex, children may clam up and wait restlessly to get out of the room. So both parents and children may feel awkward talking about sex. Why is this so?

Activity 3-1: Help! I'm Falling In Love


When hormones take over, reasoning seems to go out the window. Before you find yourself head over heels in love is the time to think about what qualities you want in a mate and how you should be treated. In this activity you create an Emergency Card to carry in your pocket. Then next time you find yourself falling in love, pull out the card and check to make sure that your emotions aren't making you forget what is important to you.


  • One copy of Activity Report per student
  • Colored pencils or thin markers
  • Heavy white paper or construction paper
  • Scissors


Step 1 Your teacher will give you an Activity Report.

Step 2 Before you write, spend some time thinking about what you would like your life to be like in the future and how you would like to be treated by a partner. If you are already involved with someone, try very hard to make sure you write down what you really want, not just what you see already exists in the other person.

Step 3 As you think, jot down your ideas on the Activity Report under the section headed What I Want in a Mate. Some examples might include-I should be treated with respect-I should not be subjected to put-downs-My partner should listen to my point of view-I would like occasional surprises. If you agree with any of these examples, you may use them, but come up with as many more as you can. Try to list at least 15. You may talk about ideas with a friend, but make sure what ever you write down is something that YOU truly believe.

Step 4 When you are satisfied with your list, think about what you consider to be the warning signs that someone is falling in love. On your Activity Report, under the heading Warning Signs of Falling in Love, write down your ideas. For example-staring into space-always thinking about the other person-wanting to always be with a particular someone. Try to come up with 15 examples or as many as you can. Think about the behavior you've observed in others.

Step 5 Next, look at the section of your Activity Report titled Caution! In this section you are to write down those things that you think might be confused with love, or might persuade you to overlook some of your requirements in a mate when you really shouldn't. Examples might include-money-gorgeous eyes-a super car-lust (strong sexual attraction only).

Step 6 When you have finished your lists, show the Activity Report to your teacher. You will be given supplies for creating a pocket Emergency Card.

Step 7 Review what you have written. Add to your list, combine things that are alike, cross out things you've changed your mind about, and edit your lists until you have about 10 items you feel strongly about in each of the first two sections, and 5 items in the Caution section.

Step 8 Decide what size you would like your card to be and if you would like it to be a single sheet like a credit card or folded like a greeting card. Cut it out.

Step 9 Decide what the layout will be. You might want to put the list What I Want in a Mate on one side, and Warning Signs of Falling in Love on the other, but remember to save some space for the Caution! section. When you're done carefully putting your lists on the card, you may go back and draw boxes or borders or decorations on the card.

Step 10 Carry your card with you, and remember to check it when you find yourself falling in love!

What Do You Think?

Why is sex so awkward to talk about?

Sexual Stimulation

Sexual experience has two basic parts-sexual stimulation and sexual response. Each part has both a physical (body) and psychological (mental) component. Both typically act together.

What Do You Think?

What are some of the most common erotic cues in our culture? Do we react to such cues naturally or do we learn to do so?

Physical stimulation occurs through the senses. People may see, hear, touch, or smell something that arouses them sexually. Such sources of stimulation act as erotic cues, or sexual triggers, that “turn us on.” Visual cues may include seeing bodies, photographs, movies, or the like. Auditory cues involve sounds, such as speech or music. Olfactory cues might be the smell of scents like perfume. Tactile stimulation consists of touching or being touched in the sensitive parts of the body.

What Do You Think?

Should advertisers exploit the attention getting power of erotic cues to sell their products? Give some examples of how advertisers exploit erotic cues to sell products.

Psychological stimulation takes two forms. It may be purely mental, such as thinking about sexual topics or making up erotic fantasies that lead to sexual arousal. But in addition, psychological factors strongly influence which physical cues from the outside world will be perceived as sexually arousing. This is why a specific sight or sound may be perceived as erotic by one person, but not by another.

Figure 3.2 Sexual stimulation and response both have physical and psychological components.

Sexual Response

Sexual response is the reaction to sexual stimulation. Like sexual stimulation, response can be physical and/or psychological.

The physical signs of sexual response depend on two types of changes in the body. The first sign of sexual response is increased blood flow into the genital organs. The most obvious sign of increased blood flow in the male is an erection of the penis. The increased blood makes it larger and harder. Think of a garden hose. When the faucet is opened, water flows into the hose and the hose gets stiff. The same mechanism works for the penis. Erection is a function of more blood going into the penis than going out of it. The stiffness of the erect penis has nothing to do with muscles or bones.

The female genital organs go through exactly the same changes. However, because of differences in their anatomy, there is no obvious sign in the female such as a male's erection. Instead, the female genital organs become slightly swollen, and the inside of the vagina becomes wet. This is called vaginal lubrication. As with erection in men, it is the first sign that a woman is sexually aroused.

The second sign of sexual response is increased muscular tension. This is not like when you consciously move your muscles to lift an object. These are very small muscles in your genital area that tense without you thinking about it. When the tension gets high, these muscles contract rhythmically, resulting in orgasm. In males, this sensation is accompanied by ejaculation during which semen, made up of sperm and fluid, is forced out of the penis. The biological purpose of ejaculation is to release semen into the vagina. But most of the time, people reach orgasm not to reproduce but to experience sexual pleasure. Women have orgasms like men do, but they do not ejaculate the same way and they do not need to reach orgasm in order to get pregnant.

What Do You Think?

If sexual arousal is a natural reaction, why does it cause some people to feel embarrassment or guilt?

Sexual excitement and orgasm are accompanied by other changes in other parts of the body as well. Blood pressure, the pulse, and the rate of breathing all increase. After orgasm, the body returns to its normal state.

The psychological reactions of sexual excitement and orgasm are harder to describe. During arousal, sexual tension builds up and is released during orgasm. This experience is intensely pleasurable, which is why sex is considered to be one of the strongest desires. It is in response to this drive that people behave sexually. However, how they behave sexually and whether or not they engage in sex depend on many other psychological and social considerations.

The main biological purpose of sex is reproduction through sexual intercourse. But there are also important psychological, emotional, and moral considerations in sexual behavior. Although sexual intercourse is the only way couples can naturally have children, the wish to become parents is only one of the reasons why men and women have sex. And as important as sexual intercourse may be for many people, it is only one form of sexual behavior and not everyone engages in it. In this section, you will learn about some of the different forms that sexual behavior takes.

In the traditional Western cultural and moral ideal, sexual intercourse between adult males and females, who are not too closely related and are married to each other, is considered the norm or the only healthy, moral, and legal sexual behavior. But this view may be inconsistent with what many people actually do.

Considerations of health, morality, and legality in sexual behaviors are important and will be discussed later in this unit. At this point, we need to have a clear understanding of what people actually do in their sexual lives, rather than what they should or should not do. And more specifically, we need to consider how young people behave sexually.

Sexual behaviors can be divided into two main groups-behaviors one engages in by oneself and behaviors one engages in with another person.

Solitary behaviors

The most common solitary sexual activity is sexual fantasy. Fantasies can be quick sexual thoughts that cross your mind or long, drawn-out erotic daydreams.

Even fairy tales talk about love, only their focus is more romantic than sexual. What romantic fantasy is typical in fairy tales like Sleeping Beauty or Cinderella? How do these compare with modem love stories? How do they compare with reality? Write a modern-day, romantic fairy tale.

Most everyone has sexual fantasies at one time or another. But some people fantasize more than others do and in different ways. Fantasies can involve thoughts about any sort of sexual activity. Since you make up your own fantasies, they usually express your sexual needs and interests. Sometimes these needs or interests may be forbidden wishes, or interests you did not know you had. Therefore, although fantasies are usually fun, they can also be scary or make you feel guilty. Remember that fantasies are just thoughts. Most of them will not come true. This is because either you cannot make them come true or you do not want them to actually happen.

Sexual fantasies serve important functions. They give some expression to sexual wishes that cannot be satisfied. Since you are in charge of your fantasies, you can remain in control.

Fantasies also help as rehearsals for what you hope may happen. For instance, when thinking about a date, or a honeymoon, the person can practice in his or her imagination to prepare for the event.

Sexual fantasies can become a problem if they absorb too much of a person's time and attention. By withdrawing into fantasy, you are less likely to interact with others and make friends. Fantasies are healthy as long as they do not interfere with social development or healthy interaction.

Fantasies that are fearful or make you feel guilty may need to be talked over with a counselor or a trusted adult. This is especially true if you think a fantasy may lead you to behave in a way that is harmful to yourself or others.

“I woke up suddenly. It was morning. I felt wet and my pajamas were sticky. Oh, God! There was something wrong with me . . . Wait a minute. Wait just a minute. Maybe I had a wet dream. Yeah. . . . I'll bet that's it. How about that?”

-Then Again, Maybe I Won't

Judy Blume

Sexual dreams are a form of fantasy that occurs during sleep. Like other dreams, they tend to be difficult to understand. Sometimes the person is sexually aroused even if the action in the dream does not seem sexual. The sexual excitement during dreams sometimes leads to orgasm. These are called nocturnal orgasm (nocturnal means nighttime). Both boys and girls experience nocturnal orgasms. They are more likely to be remembered by boys because ejaculation wets the bedding or underwear (hence wet dreams). Girls also may have orgasms in their sleep, but they do not ejaculate. These are perfectly normal ways of the body releasing its sexual tension.

Did You Know?

In 1994, the U.S. surgeon general was fired from her job after talking in public about masturbation as an alternative to sexual intercourse. The public acknowledgment or acceptance of masturbation as a normal human behavior has always been, and remains today, a controversial issue.

Sexual fantasies can also occur through self-stimulation of the genitals, called masturbation. Many people masturbate, sometimes because they have no sexual partner, but also as another way of reaching orgasm. Masturbation is like fantasy in many ways. It is usually a solitary activity. Along with sexual fantasies, masturbation makes it possible for a person to get sexual satisfaction without having to rely on someone else and without engaging in risky behavior. Although many people masturbate, no one has to do it. It is a matter of choice.

In the past, masturbation was thought to be physically harmful. Doctors claimed that the practice weakened the body, especially when one is growing up. All sorts of fanciful dangers were attributed to it; the brain would go soft, the person would become crazy, the heart would fail, the breath would smell bad, and so on. None of this is true. Masturbation causes no physical ill effects.

What Do You Think?

Do you think masturbation should be promoted to adolescents as an alternative to sexual intercourse? Why or why not?

Masturbation is the safest way of experiencing orgasm. It does not cause pregnancy or sexually transmitted diseases. In this period of the AIDS epidemic, it is one of the safest forms of sex. Nonetheless, some people continue to object to masturbation on psychological or moral grounds.

For most people, masturbation alone cannot satisfy all of their sexual needs. It does not have the rich emotional satisfactions of having sexual intercourse with someone who is loved. A person cannot impregnate or become pregnant by masturbating. But even for many married people, masturbation may be an occasional source of sexual satisfaction.

Sociosexual Behaviors

The most important human activities involve other people. Sex is no exception. Sociosexual behaviors are those sexual acts done with other people. The most common form of sociosexual sex is sexual intercourse. It is also called having sex or sleeping together. There are also many slang terms used to describe the act of sexual intercourse.

Sexual intercourse is the one activity approved of by all societies. Yet it is also always subject to rules and restrictions about whom one can and cannot have sex with. These rules can be based on how old someone is or the partner is; how closely the partners are related; whether they are married to each other or not; and so on.

In physical terms, sexual intercourse involves the penis moving in and out of the vagina. However, sexual intercourse is not just a physical act. For many couples, it is a means of expressing intimacy and love as well as experiencing sexual pleasure. But sexual intercourse can be used in a harmful or negative way by deceiving or coercing others into it against their will. Also, unprotected intercourse carries serious risk of unwanted pregnancy and sexually transmitted diseases.

Sexual intercourse is usually initiated by activities like kissing, caressing, and similar forms of sexual stimulation, which are called foreplay. However, couples also engage in such behavior without going on to have sexual intercourse. In these cases, these behaviors are called petting, necking, sex play, and similar terms.

Did You Know?

Same sex crushes during adolescence are very common and normal. Boys may feel curious about boys, and girls may be curious about girls. They may even touch each other's bodies or dream about one another. These usually do not imply homosexuality-typically, these feelings only reflect an emerging sense of sexuality.

Those who are romantically or sexually attracted to members of the opposite sex have a heterosexual orientation. Those who are similarly attracted to members of the same sex have a homosexual orientation. The majority of men and women are heterosexual, but we do not have an accurate count of what proportion of the population is homosexual. The most reliable figures show that 2-3% of men and 1% of women are exclusively homosexual, although twice as many have actually engaged in homosexual acts or felt sexually attracted to someone of the same sex sometime during their lifetime.

Some scientists explain the development of sexual orientation by genetic and hormonal causes. Others point to psychological or social factors having to do with how one is brought up. Probably both types of factors play a role.

You have just found out that someone you know and respect is a homosexual. You have always seen this person as being very heterosexual. You are very surprised and need to sort through your feelings before you see this person again. Write a diary entry to yourself or a letter to your friend exploring your thoughts and attitudes.

In our culture, homosexual behavior has long been considered abnormal and condemned on moral and legal grounds. Currently, homosexuality is no longer considered to be a psychological abnormality by most psychiatrists or psychologists, and it is no longer against the law in the United States. However, there are still people who find it objectionable for moral or other reasons. Also, the law still does not permit homosexual marriages. Social attitudes in this respect have changed greatly during the recent past and continue to do so.

There are some sexual behaviors that are socially unacceptable. These include forcing someone to have sex or having sex with persons who are not adults. These topics will be discussed later in this unit in connection with other sexual problems.

Review Questions

  1. Is the sexual drive correlated with or caused by hormones? Explain.
  2. How does human sexual behavior differ from animal sexual behavior?
  3. Draw a diagram showing the relationship of sexual arousal, sexual response, and the physical and psychological components. Explain what sexual response to arousal includes.
  4. What are some examples of erotic cues?
  5. Describe three solitary sexual behaviors and the role they play in a person's life.
  6. How is sexual orientation determined?

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