10.1 Sex and Sexuality

sexuality and gender

Let’s Talk About Sex

I’ll Be Your Nurse Today Stephen Patten has been a nurse for over three decades. He has worked in the trenches, treating gunshot and stab wounds in trauma centers, and he has held important leadership positions, serving as director of a hospital tissue bank and president of the National Association of Clinical Nurse Specialists (2012–2013).

D. Michael Moody Medical Photographer, Medical Media Production Service

When people talk about sex, they often are referring to a sexual act such as intercourse. But sex can also refer to the classification of people as male or female, a distinction based on genetic composition and the structure and/or function of reproductive organs (Pryzgoda & Chrisler, 2000). Gender, on the other hand, refers to the dimension of masculinity and femininity based on social, cultural, and psychological characteristics. The American Psychological Association (APA, 2010c, 2011a) recommends using the term “sex” when referring to biological status and “gender” for the cultural roles and expectations that distinguish males and females. According to the American Psychiatric Association (APA, 2013), “gender” also indicates the public and often legally recognized role a person has as a man or woman, boy or girl.

From your reading of other chapters in this book, you know that psychologists often view behaviors as resulting from an interaction of biological, psychological, and social forces. We will use this biopsychosocial perspective to emphasize the role these factors play in our sexuality. In other words, how they influence our sexual activities, attitudes, and behaviors.

Sex: It’s In Your Biology

What are the topics of sex and gender doing in a psychology textbook, and are they important enough to merit their own chapter? Sex and gender play a role in the scientific study of behavior and mental processes, serving as important variables to be studied. And you know intuitively that relationships and emotions related to sexuality are a part of what makes us human.

Note: Quotations attributed to Stephen Patten and Dr. Stephanie Buehler are personal communications.

Sexual Healing Dr. Stephanie Buehler is a certified sex therapist. She helps couples and individuals resolve sexual problems, including low desire, erectile dysfunction, pain during intercourse, and confusion about sexual orientation. Sex therapy is a rapidly advancing field, as researchers continue to develop and test new approaches to treatment (Althof, 2010).

Mark Buehler

In this chapter, you will learn about the biology of sexual determination and differences of sex development, and explore how sex influences human behavior. Sex is one of the most intimate—and fascinating—dimensions of human behavior. It is also one of the most difficult to study.

A very personal topic for most people, sex is not openly discussed in many homes, schools, doctors’ offices, or even bedrooms in North America (Byers, 2011). This is ironic, given that North American culture supplies a steady stream of sexual imagery, words, and media. Many parents feel embarrassed discussing sex with their children. Medical and mental health professionals find it difficult to communicate with patients about sexual issues. Some of us cannot even talk honestly about sex with our sexual partners.

Researchers use a variety of approaches to study human sexuality, including surveys, interviews, case studies, and the experimental method. There are also many technologies to observe and measure physiological responses (Chivers, Seto, Lalumiere, Laan, & Grimbos, 2010). For example, MRI and fMRI can be used to study sexual arousal during intercourse and other sexual activities (Schultz, van Andel, Sabelis, & Mooyaart, 1999).

But as you can imagine, studying sexual behavior has its difficulties. People are often uncomfortable discussing sex, especially their own sex lives, so getting participants to open up can be tricky. The extreme intimacy many people feel about their sexuality can also make research that includes the observation of sexual behavior especially challenging. As a result, our knowledge of sexual behavior is often limited to self-reporting. Yet there are problems with relying on self-reported data, including the tendency for some people to be dishonest or portray themselves in the best possible light. There are ways to sidestep these issues, however. For example, Rieger and Savin-Williams (2012) had participants view short video clips of images that were neutral (landscape) or sexually explicit (male or female models masturbating). Given that our pupils dilate when we are sexually aroused, the researchers were able to use this variable as an index of sexual arousal. They measured the degree to which participants’ pupils dilated when they looked at neutral versus sexually explicit images, gauging the participants’ sexual arousal without being too intrusive.

Not everyone is shy about personal sexual behavior, of course, and that is good news for researchers. Participants in human sexuality studies engage in a variety of sexual activities, including sexual intercourse and masturbation, with approval from Institutional Review Boards (IRBs) to ensure ethical treatment.

Now it’s time to delve into the heart of the chapter. Get ready to explore the many facets of sexuality and gender.

The Biology of Sexual Determination

A person’s sex (male or female) depends on both genes and hormones. Sex determination refers to the designation of genetic sex, which guides the activity of hormones that direct the development of reproductive organs and structures (Ngun, Ghahramani, Sánchez, Bocklandt, & Vilain, 2011). Let’s take a closer look at how all this works.

Your genetic sex was determined by your father’s sperm. In the moment of conception, dad’s sperm united with mom’s egg to form a zygote. A zygote contains genetic material from both parents in the form of 46 chromosomes—23 from mom, 23 from dad. These chromosomes provide the blueprint for biological development, including that of the physiological structures associated with sex. The 23rd pair of chromosomes, also referred to as the sex chromosomes, includes specific instructions for the zygote to develop into a female or a male. It’s as simple as X and Y.

The egg from the mother carries an X chromosome, and the sperm from the father carries either an X chromosome or a Y chromosome. When the sperm contributes an X chromosome to the 23rd pair, the genetic sex is XX, and the zygote generally develops into a female. If the sperm carries a Y chromosome, the genetic sex is XY, and the zygote typically develops into a male. About 50% of sperm carry the X chromosome, and 50% carry the Y chromosome. This is the reason the population is approximately half male and half female.

23 Pairs A typical person has 23 pairs of chromosomes (46 total) in almost every cell. The 23rd pair, also referred to as the sex chromosomes, contains genes that determine the sex of the developing person. If the 23rd pair is XY, then the zygote will develop into a male; if XX, it will become a female. Can you tell what genetic sex is represented here? (See bottom of column for answer.)

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From the moment a zygote is formed, genetic sex is constant. In other words, the composition of the 23rd pair of chromosomes remains female (XX) or male (XY). We should note, however, that the structure and function of the reproductive organs do not always match the original genetic sex (XX or XY). The development of reproductive anatomy is influenced by a variety of factors, including interactions among genes and the activity of hormones produced by the sex glands (also known as gonads) of the fetus (Blecher & Erickson, 2007; Dennis, 2004). For the sake of the discussion here, we’ll assume that the genetic sex matches the developing physical characteristics.

In a genetic male, the presence of the Y chromosome causes the gonads to become testes. If the Y chromosome is not present, as in the case of a genetic female, then the gonads develop into ovaries (Hines, 2011a). Both the testes and ovaries secrete hormones that influence the development of reproductive organs: androgens in the case of the testes and estrogen in the case of the ovaries. (These sex hormones are also secreted by the adrenal glands in both males and females.) Testosterone, for example, is an androgen that influences whether the fetus develops male or female genitals.

Even though the genetic sex of the fetus is determined at conception, it is not possible to ascertain the sex until 7 weeks after conception through blood tests (Devaney, Palomaki, Scott, & Bianchi, 2011). Fetal genital anatomy can be determined by ultrasound by the end of the first trimester (Scheffer et al., 2010). But it is usually not until adolescence that the sex structures kick into reproductive action. Puberty begins, and the cycle of life is poised to continue.

Puberty is a period when notable changes occur in physical development, ultimately leading to sexual maturity and the ability to reproduce. During this time, the primary and secondary sex characteristics develop (Figure 10.1). In addition, one of the most significant changes for males is spermarche, or first ejaculation (often occurring during sleep). The equivalent for females is menarche, or first menstruation (Ladouceur, 2012; Mendle, Harden, Brooks-Gunn, & Graber, 2010).

FIGURE 10.1Physical Changes at PubertyDuring puberty, the body changes and becomes sexually mature and able to reproduce. The primary sex characteristics mature, and the secondary sex characteristics become more distinct. Primary sex characteristics are related to reproductive organs. The reproductive organs, present at birth, begin to function differently at puberty. For instance, the testes and ovaries are involved in stimulating more visible changes, such as breast development and growth of the penis.

Vive la Différence

Apart from the obvious physical differences between the sexes, what else distinguishes males and females? Adult male brains, on average, are approximately 10% larger than adult female brains (Feis, Brodersen, von Cramon, Luders, & Tittgemeyer, 2013). There are also structural disparities in the brain; for example, the cerebral hemispheres are not completely symmetric, and males and females differ somewhat in these asymmetries (Tian, Wang, Yan, & He, 2011). MRI analyses point to sex differences in the brain networks involved in social cognition and visual-spatial abilities (Feis et al., 2013). Some distinctions between male and female brains are believed to be influenced by hormones secreted prenatally, suggesting they have a biological basis (Sanders, Sjodin, & de Chastelaine, 2002).

Despite these contrasts in brain size and structure, males and females do not differ significantly in terms of general intelligence (Burgaleta et al., 2012; Halpern et al., 2007), a pairing many researchers find remarkable: “Apparently, males and females can achieve similar levels of overall intellectual performance by using differently structured brains in different ways” (Deary, Penke, & Johnson, 2010, p. 209). Researchers do find different patterns of neurological activity in males and females, but remember that brains can change in response to experience, a phenomenon called neuroplasticity. Sex differences may be due to changes in synaptic connections and neural networks that result from the different experiences of being male or female (Hyde, 2007).

What are some of the functional differences between male and female brains? One important area of difference is mental rotation; studies suggest that men are better than women at mentally rotating objects (Collins & Kimura, 1997). With practice, women may be able to catch up, however. In one study, women who practiced mentally rotating objects while playing computer games showed greater improvement on measures of mental rotation than did the men (Cherney, 2008). Another area of difference is verbal competence. In childhood, girls tend to perform better on tests of verbal ability, but the discrepancies are so small that they don’t provide useful information for making educational decisions (Hyde & Linn, 1988; Wallentin, 2009). Differences in cognitive development between boys and girls are “minimal,” and these disparities are only responsible for a small proportion of the variability in children’s scores on cognitive tasks (Ardila, Rosselli, Matute, & Inozemtseva, 2011).

Research suggests that some cognitive gender disparities carry over into adulthood, with women outperforming men in verbal tasks and men showing greater spatial and mathematical abilities. These differences between men and women have declined over the past several decades, suggesting changes in sociocultural factors, such as greater availability of advanced math courses and more support for both men and women to pursue careers that interest them (Deary et al., 2010; Wai, Cacchio, Putallaz, & Makel, 2010). When it comes to mathematics performance in children, gender is not the best predictor; environmental factors such as mother’s education, the learning environment of the home, and effectiveness of the elementary school are “far stronger predictors” (Lindberg, Hyde, Petersen, & Linn, 2010).

We’ve discussed gender disparities in brain anatomy and cognitive abilities, but how do males and females differ in terms of behavior? Men tend to demonstrate more physical aggression (such as hitting) than females (Ainsworth & Maner, 2012; see Chapter 15), but that doesn’t mean females aren’t aggressive in their own way. Some researchers report that females exhibit more relational aggression, or aggressive behaviors that are indirect and aimed at relationships, such as spreading rumors or excluding certain group members (Archer, 2004; Archer & Coyne, 2005; Crick & Grotpeter, 1995). These gender differences typically appear early in life (Card, Stucky, Sawalani, & Little, 2008; Hanish, Sallquist, DiDonato, Fabes, & Martin, 2012).

What causes these differences in males and females? One hormonal candidate is testosterone, which has been associated with aggression (Montoya, Terburg, Bos, & van Honk, 2012) and, as discussed earlier, exists at higher levels in males. Studies of identical twins suggest that approximately 50% of aggressive behavior can be explained by genetic factors (DiLalla, 2002; Tackett, Waldman, & Lahey, 2009). This implies that a significant proportion of gender differences in aggressive behavior results from an interaction between environmental factors and genetics (Brendgen et al., 2005; Rowe, Maughan, Worthman, Costello, & Angold, 2004). In addition, researchers have noted that boys tend to be more aggressive when raised in nonindustrial societies; patriarchal societies, in which women have less power and are considered inferior to men; and polygamous societies, in which men can have more than one wife. Why are these males more aggressive? Evolutionary psychology would suggest that competition for resources (including females) increases the likelihood of aggression (Wood & Eagly, 2002).

Tragic Outcome Viewing Amanda Todd’s famous YouTube video is heartrending. Todd was just 15 years old when she took her own life, a tragedy many people believe resulted from years of being bullied and harassed online and at school (Shaw, 2013, March 13). Most of the abuse Todd suffered took the form of relational aggression, a type of aggression that is not physical but extremely hurtful (Archer & Coyne, 2005). The ongoing threats, rumors, and gossip drove her to become anxious, depressed, and eventually suicidal (Shaw, 2013, March 13).

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One thing to keep in mind is that, overall, the variation within a gender is much greater than the variation between genders: “Males and females are similar on most, but not all, psychological variables” (Hyde, 2007, p. 260). This gender similarities hypothesis proposed by Hyde (2005) states that males and females exhibit large differences in only a few areas, including some motor behaviors (throwing distance), some characteristics of sexuality (frequency of masturbation), and to a moderate degree, aggression. These physical and behavioral differences between males and females are interesting, but keep in mind that sex development does not always occur along a strictly “male” or “female” path.

Differences of Sexual Development

In some cases, hormonal imbalances and genetic abnormalities lead to differences of sex development (Topp, 2013; Infographic 10.1). Such disparities result from “congenital conditions in which development of chromosomal, gonadal, or anatomic sex is atypical” (Lee, Houk, Ahmed, & Hughes, 2006, p. e488). According to the American Psychiatric Association (2013, p. 451), intersexual refers to having “conflicting or ambiguous biological indicators” of male or female in sexual structures and organs (TABLE 10.1). For example, intersexual development would be apparent in a genetic female (XX) or male (XY) who has sexual structures and organs that are ambiguous or inconsistent with genetic sex. Around 1% of infants are found to have differences of sex development at birth. Such an individual might once have been called a “hermaphrodite,” but this term is outdated, derogatory, and misleading because it refers to the impossible condition of being both fully male and fully female (Vilain, 2008).

The roots of intersexuality lie early in development, when fetal sensitivity to hormones determines the path of sexual differentiation, with timing and the amount of hormones as important factors. If a male fetus is insensitive to androgens, for example, he may develop more femalelike sex organs (known as androgen insensitivity syndrome; Mazur, 2005). A fetally androgenized female develops more malelike sex organs as a result of being exposed to excess androgens (Dessens, Slijper, & Drop, 2005).

Differences of sexual development can also be traced to irregularities in the sex chromosomes, as the creation of the 23rd pair does not always follow the expected pattern of XX or XY (Juul, Main, & Skakkebaek, 2011; Wodrich & Tarbox, 2008). On some occasions, there are too many chromosomes or one missing. In the case of Klinefelter’s syndrome, a male is born with at least one extra X chromosome in the 23rd pair (for example, XXY). A boy with Klinefelter’s syndrome typically develops normally until puberty, but then has a greater chance of developing female sex characteristics such as breasts. He is infertile or may have underdeveloped sexual organs and secondary sex characteristics (Mandoki, Sumner, Hoffman, & Riconda, 1991; Manning, Kilduff, & Trivers, 2013). In Turner’s syndrome, a female is born with only one X chromosome (as opposed to two X chromosomes), anatomically normal genitals, ovaries that are not fully developed, and infertility. Girls with this syndrome who go undiagnosed or untreated are at increased risk for estrogen deficiency, hypothyroidism, cardiovascular issues, and short stature (Hjerrild, Mortensen, & Gravholt, 2008). Despite the possibility of developmental delays in cognitive, social, and emotional functioning, women with Turner’s syndrome who receive treatment can lead independent, stable, and productive lives (McCauley & Sybert, 2006).

INFOGRAPHIC 10.1: Different Layers of Sexual Determination

When thinking about the biological factors that determine sex, most people envision the primary sex characteristics that indicate our assignment at birth. But one’s sex is made up of many layers with different influences. Though they often all combine in a predictable way, there can be exceptions at any point. Looking at variations at each layer demonstrates the complex reality of sex that goes far beyond what is declared on our birth certificates.