Psychology: Unit 4.2 Im. P

Simply said, your body defines your sex. Your mind defines your gender. But your mind's understanding of gender arises from the interplay between your biology and your experiences (Eagly & Wood, 2013).

The meanings of Sex vs gender.

Our genes form us. This is a great truth about human nature.

A great truth about human nature.

Sex differences in the way we interact with others begin to appear at a very young age.

Appearance of sex differences in interactions with others.

RP-3 __________(Men/Women) are more likely to commit relational aggression, and __________ (men/women) are more likely to commit physical aggression.

ANSWER: Women; men

RP-1 Put the following cell structures in order from smallest to largest: nucleus, gene, chromosome.

ANSWER: gene, chromosome, nucleus

RP-4 Prenatal sexual development begins about __________ weeks after conception. Adolescence is marked by the onset of __________.

ANSWER: seven; puberty

Think of examples of aggressive people. Are most of them men? Likely yes. Men generally admit to more aggression, especially extreme physical violence (Bushman & Huesmann, 2010; Wölfer & Hewstone, 2015). In romantic relationships between men and women, minor acts of physical aggression, such as slaps, are roughly equal, but the most violent acts are mostly committed by men (Archer, 2000; Johnson, 2008).

Aggression in men.

Androgyny has benefits. As adults, androgynous people are more adaptable. They are more flexible in their actions and in their career choices (Bem, 1993). They tend to be more resilient and self-accepting, and they experience less depression (Lam & McBride-Chang, 2007; Mosher & Danoff-Burg, 2008; Ward, 2000).

Androgyny in gender explained.

Behavior reflects social norms and roles.

Attributing behavior in Collectivism.

Behavior reflects the individual's personality and attitudes.

Attributing behavior in Individualism.

But in general, people (especially men) in competitive, individualist cultures have more personal freedom, are less geographically bound to their families, enjoy more privacy, and take more pride in personal achievements.

Benefits of individualism.

Common chimpanzees and bonobos resemble each other in many ways. They should—their genomes differ by much less than 1 percent. But they display markedly differing behaviors. Chimpanzees are aggressive and male-dominated. Bonobos are peaceable and female-led.

Chimpanzees and Bonobos compared.

Collectivists are like athletes who take more pleasure in their team's victory than in their own performance. They find satisfaction in advancing their groups' interests, even at the expense of personal needs. They preserve group spirit by avoiding direct confrontation, blunt honesty, and uncomfortable topics. They value humility, not self-importance (Bond et al., 2012). Instead of dominating conversations, collectivists hold back and display shyness when meeting strangers (Cheek & Melchior, 1990). Given the priority on "we," not "me," that individualized North American latte might sound selfishly demanding in Seoul (Kim & Markus, 1999).

Collectivism explained.

The stunning finding from studies of hundreds of adoptive families is that, apart from identical twins, people who grow up together, whether biologically related or not, do not much resemble one another in personality (McGue & Bouchard, 1998; Plomin, 2011; Rowe, 1990). In personality traits such as extraversion and agreeableness, for example, people who have been adopted are more similar to their biological parents than their caregiving adoptive parents.

DIfferences between adopted siblings.

Early humans disposed to eat nourishing rather than poisonous foods survived to contribute their genes to later generations. Those who deemed leopards "nice to pet" often did not.

Development of the shared human genome explained.

And how did we develop this shared human genome? At the dawn of human history, our ancestors faced certain questions: Who is my ally, who is my foe? With whom should I mate? What food should I eat? Some individuals answered those questions more successfully than others.

Development of the shared human genome.

But in some areas, males and females do differ, and differences command attention. Some oft-noted differences (like the difference in self-esteem shown in FIGURE 12.4) are actually quite modest (Zell et al., 2015). Others are more striking. The average girl enters puberty about a year earlier than the average boy, and a woman's life span is 5 years longer. She expresses emotions more freely, smiling and crying more, and, in Facebook updates, more often expresses "love" and being "sooo excited!!!" (Fischer & LaFrance, 2015; Schwartz et al., 2013). She can detect fainter odors, receives offers of help more often, and can become sexually re-aroused sooner after orgasm. She also has twice the risk of developing depression and anxiety and 10 times the risk of developing an eating disorder. Yet the average man is 4 times more likely to die by suicide or to develop an alcohol use disorder. His "more likely" list also includes autism spectrum disorder, color-deficient vision, and attention-deficit/hyperactivity disorder (ADHD). And as an adult, he is more at risk for antisocial personality disorder. Male or female, each has its own share of risks.

Differences between males & females.

Brain maturation provides us with an abundance of neural connections. Experience—sights and smells, touches and tastes, music and movement—activates and strengthens some neural pathways while others weaken from disuse. Similar to paths through a forest, less-traveled neural pathways gradually disappear and popular ones are broadened (Gopnik et al., 2015).

Effect of experience on neural pathways.

The typical genetic difference between two Icelandic villagers or between two Kenyans is much greater than the average difference between the two groups. Thus, if after a worldwide catastrophe only Icelanders or Kenyans survived, the human species would suffer only "a trivial reduction" in its genetic diversity (Lewontin, 1982)

Effect of the shared human genome explained.

Our similarities arise from our shared human genome, our common genetic profile. No more than 5 percent of the genetic differences among humans arise from population group differences. Some 95 percent of genetic variation exists within populations (Rosenberg et al., 2002).

Effect of the shared human genome.

Stimulation by touch or massage also benefits infant rats and premature babies (Field et al., 2007; Sarro et al., 2014). "Handled" infants of both species develop faster neurologically and gain weight more rapidly. Preemies who have had skin-to-skin contact with their mothers sleep better, experience less stress, and show better cognitive development 10 years later (Feldman et al., 2014).

Effect of touch/massage on the development of rats & babies.

The normal range of environments shared by a family's children has little discernible impact on their personalities.

Environmental impact on the personality of siblings.

They use Charles Darwin's principle of natural selection—"arguably the most momentous idea ever to occur to a human mind," said Richard Dawkins (2007)—to understand the roots of behavior and mental processes.

Evolutionary Psychologists explained.

Evolutionary psychologists also agree with their critics that some traits and behaviors, such as suicide, are hard to explain in terms of natural selection (Barash, 2012; Confer et al., 2010). But they ask us to remember evolutionary psychology's scientific goal: to explain behaviors and mental traits by offering testable predictions using principles of natural selection. We may, for example, predict that people are more likely to perform favors for those who share their genes or can later return those favors. Is this true? (The answer is Yes.) And evolutionary psychologists remind us that studying how we came to be, need not dictate how we ought to be. Understanding our tendencies can help us overcome them.

Evolutionary Psychology's compromise.

Environmental factors such as diet, drugs, and stress can affect the epigenetic molecules that regulate gene expression.

Factors that can affect Epigenetics.

Freudian psychiatry and psychology encouraged such ideas by blaming problems from asthma to schizophrenia on "bad mothering." Believing that parents shape their offspring as a potter molds clay, many people praise parents for their children's virtues and blame them for their children's vices, and for the psychological harm that toxic parents presumably inflict on their fragile children. No wonder having and raising children can seem so risky.

Freudian view of good and bad parenting.

But no matter how much parents encourage or discourage traditional gender behavior, children may drift toward what feels right to them. Some organize themselves into "boy worlds" and "girl worlds," each guided by their understanding of the rules. Others conform to these rules more flexibly. Still others seem to prefer androgyny: A blend of male and female roles feels right to them.

Gender differences in children.

Regardless of personality differences between adoptive family members, most adopted children benefit from adoption.

Growing up adopted.

Girls' slightly earlier entry into puberty can at first propel them to greater height than boys of the same age (FIGURE 12.5). But boys catch up when they begin puberty, and by age 14, they are usually taller than girls. During these growth spurts, the primary sex characteristics—the reproductive organs and external genitalia—develop dramatically. So do the nonreproductive secondary sex characteristics. Girls develop breasts and larger hips. Boys' facial hair begins growing and their voices deepen. Pubic and underarm hair emerges in both girls and boys (FIGURE 12.6).

Growth Spurts in Puberty.

Moreover, it now appears that some epigenetic changes are passed down to future generations.

Hereditary Epigenetic traits.

For many personality traits, heritability is about 40 percent; for general intelligence, heritability has been estimated at about 66 percent (Haworth et al., 2010; Turkheimer et al., 2014). This does not mean that your intelligence is 66 percent genetic. Rather, it means that genetic influence explains about 66 percent of the observed variation among people.

Heritability of personality traits.

If genetic influences help explain variations in traits among individuals in a group, can the same be said of trait differences between groups? Not necessarily. Height is 90 percent heritable, yet nutrition (an environmental factor) rather than genes explains why, as a group, today's adults have grown (Floud et al., 2011).

Heritability vs Environment explained.

Genes matter, but so does environment.

Heritability vs Environment in a nutshell.

As environments become more similar, heredity becomes the primary source of differences. If all schools were of uniform quality, all families equally loving, and all neighborhoods equally healthy, then heritability would increase (because differences due to environment would decrease). But consider the other extreme: If all people had similar heredities but were raised in drastically different environments (some in barrels, some in luxury homes), heritability would be much lower.

Heritability vs Environment.

Thanks to our culture's mastery of language, we humans enjoy the preservation of innovation. Within the span of this day, we have used Google, smartphones, digital hearing technology [DM], and a GPS running watch [ND]. On a grander scale, we have culture's accumulated knowledge to thank for the last century's 30-year extension of the average human life expectancy (in most countries where this book is being read).

Human Culture today.

As with height and weight, so with personality and intelligence scores: Heritable individual differences need not imply heritable group differences. And, if some individuals are genetically disposed to be more aggressive than others, that needn't explain why some groups are more aggressive than others. Putting people in a new social context can change their aggressiveness. Today's peaceful Scandinavians carry many genes inherited from their Viking warrior ancestors.

Individual vs group heritable differences.

Discover and express one's uniqueness.

Individualism & Life task.

Many, often temporary or casual; confrontation acceptable.

Individualism & Relationships.

Individualists do share the human need to belong. They join groups. But they are less focused on group harmony and doing their duty to the group (Brewer & Chen, 2007). Being more self-contained, individualists move in and out of social groups more easily. They feel relatively free to switch places of worship, change jobs, or even leave their extended families and migrate to a new place. Marriage is often for as long as they both shall love.

Individualism explained.

Do such findings mean that women are just more talkative? No. In another study, researchers counted the number of words 396 college students spoke in an average day (Mehl et al., 2007). Not surprisingly, the participants' talkativeness varied enormously—by 45,000 words between the most and least talkative. (How many words would you guess you speak a day?) Contrary to stereotypes of wordy women, both men and women averaged about 16,000 words daily.

Loquaciousness in men & women.

For boys, puberty's landmark is the first ejaculation, which often occurs first during sleep (as a "wet dream"). This event, called spermarche, usually happens by about age 14.

Male puberty landmark.

Across our cultural differences, we even share a "universal moral grammar" (Mikhail, 2007). Men and women, young and old, liberal and conservative, living in Sydney or Seoul, all respond negatively when asked, "If a lethal gas is leaking into a vent and is headed toward a room with seven people, is it okay to push someone into the vent—saving the seven but killing the one?" And they all respond more approvingly when asked if it's okay to allow someone to fall into the vent, again sacrificing one life but saving seven.

Morality in the shared human genome.

Certain biological and behavioral variations increase organisms' reproductive and survival chances in their particular environment.

Natural Selection simplified.

Offspring that survive are more likely to pass their genes to ensuing generations.

Natural Selection simplified.

Organisms' varied offspring compete for survival.

Natural Selection simplified.

Over time, population characteristics may change.

Natural Selection simplified.

Our genes, when expressed in specific environments, influence our developmental differences. We are like coloring books, with certain lines predisposed and experience filling in the full picture.

Our developmental differences.

The plans for your own book of life run to 46 chapters—23 donated by your mother's egg and 23 by your father's sperm. Each of these 46 chapters, called a chromosome, is composed of a coiled chain of the molecule DNA (deoxyribonucleic acid). Genes, small segments of the giant DNA molecules, form the words of those chapters.

Our genetic makeup described.

As children mature, what other experiences do the work of nurturing? At all ages, but especially during childhood and adolescence, we seek to fit in with our groups (Harris, 1998, 2000):

Peer influence in development.

Feelings matter, but so does how we think. Early in life, we all form schemas, or concepts that help us make sense of our world. Our gender schemas organize our experiences of male-female characteristics and help us think about our gender identity, about who we are (Bem, 1987, 1993; Martin et al., 2002).

Personal development of gender.

In this two-year period of rapid sexual maturation, pronounced male-female differences emerge. A variety of changes begin at about age 11 in girls and at about age 12 in boys, though the subtle beginnings of puberty, such as enlarging testes, appear earlier (Herman-Giddens et al., 2012). A year or two before the physical changes are visible, girls and boys often feel the first stirrings of sexual attraction (McClintock & Herdt, 1996).

Puberty explained.

In girls, the landmark is the first menstrual period, menarche, usually within a year of age 12½ (Anderson et al., 2003). Genes play a major role in predicting when girls experience menarche (Perry et al., 2014). But environment matters, too. Early menarche is more likely following stresses related to father absence, sexual abuse, insecure attachments, or a history of a mother's smoking during pregnancy (Rickard et al., 2014; Shrestha et al., 2011; Sung et al., 2016). In various countries, girls are developing breasts earlier (sometimes before age 10) and reaching puberty earlier than in the past. Suspected triggers include increased body fat, diets filled with hormone-mimicking chemicals, and, possibly, greater stress due to family disruption (Biro et al., 2010, 2012; Ellis et al., 2012; Herman-Giddens, 2013).

Puberty landmarks in females.

ANSWER: Over multiple generations, Belyaev and Trut selected and bred foxes that exhibited a trait they desired: tameness. This process is similar to naturally occurring selection, but it differs in that natural selection is much slower, and normally favors traits (including those arising from mutations) that contribute to reproduction and survival.

RP-1 How are Belyaev and Trut's breeding practices similar to, and how do they differ from, the way natural selection normally occurs?

ANSWER: Evolutionary psychologists theorize that females have inherited their ancestors' tendencies to be more cautious sexually because of the challenges associated with incubating and nurturing offspring. Males have inherited a tendency to be more casual about sex, because their act of fathering requires a smaller investment.

RP-2 How do evolutionary psychologists explain male-female differences in sexuality?

ANSWER: Individualists give priority to personal goals over group goals and tend to define their identity in terms of their own personal attributes. Collectivists give priority to group goals over individual goals and tend to define their identity in terms of group identifications.

RP-2 How do people in individualist and collectivist cultures differ?

Here's another question: Think of examples of people harming others by passing along hurtful gossip, or by shutting someone out of a social group or situation. Were most of those people men? Perhaps not. Those behaviors are acts of relational aggression, and women are slightly more likely than men to commit them (Archer, 2004, 2007, 2009).

Relational aggression in women.

Cultures shape our behaviors by defining how we ought to behave in a particular social position, or role. We can see this shaping power in gender roles—the social expectations that guide our behavior as men or as women.

Roles assigned by culture.

Human nature, noted Roy Baumeister (2005), seems designed for culture. We are social animals, but more. Wolves are social animals; they live and hunt in packs. Ants are incessantly social, never alone. But "culture is a better way of being social," observed Baumeister. Wolves function pretty much as they did 10,000 years ago. We enjoy countless things that were unknown to our century-ago ancestors. Culture works.

Roy Baumeister (2005) on Human Nature & Culture.

Although identical twins have the same genes, they don't always have the same number of copies of those genes repeated within their genome. That variation helps explain why one twin may have a greater risk for certain illnesses and disorders, including schizophrenia (Maiti et al., 2011). Most identical twins share a placenta during prenatal development, but one of every three sets has separate placentas. One twin's placenta may provide slightly better nourishment, which may contribute to a few identical twin differences (Marceau et al., 2016; van Beijsterveldt et al., 2016).

Small differences in identical twins.

Brain scans do, however, suggest that a woman's brain, more than a man's, is wired in a way that enables social relationships (Ingalhalikar et al., 2013). This helps explain why females tend to be more interdependent. In childhood, girls usually play in small groups, often with one friend. They compete less and imitate social relationships more (Maccoby, 1990; Roberts, 1991). Teen girls spend more time with friends and less time alone (Wong & Csikszentmihalyi, 1991). In late adolescence, they spend more time on social networking sites, and average twice as many text messages per day as boys (Lenhart, 2015a; Pryor et al., 2007, 2011). Girls' and women's friendships are more intimate, with more conversation that explores relationships (Maccoby, 2002)

Social connectedness in females.

Defined by the individual (self-based).

The Morality of Individualism.

Temperament differences typically persist. The most emotionally reactive newborns tend also to be the most reactive 9-month-olds (Wilson & Matheny, 1986; Worobey & Blajda, 1989). Emotionally intense preschoolers tend to become relatively intense young adults (Larsen & Diener, 1987). In one study of more than 900 New Zealanders, emotionally reactive and impulsive 3-year-olds developed into somewhat more impulsive, aggressive, and conflict-prone 21-year-olds (Caspi, 2000).

Temperament and development.

Identical twins, more than fraternal twins, often have similar temperaments (Fraley & Tancredy, 2012; Kandler et al., 2013).

Temperament in twins.

Defined by social networks (duty-based).

The Morality of Collectivism.

Many people of faith find the scientific idea of human origins congenial with their spirituality. In the fifth century, St. Augustine (quoted by Wilford, 1999) wrote, "The universe was brought into being in a less than fully formed state, but was gifted with the capacity to transform itself from unformed matter into a truly marvelous array of structures and life forms." Some 1600 years later, Pope Francis in 2014 welcomed a science-religion dialogue, saying, "Evolution in nature is not inconsistent with the notion of creation, because evolution requires the creation of beings that evolve."

The agreement of Faith and science on human origins.

Seven in eight adopted children have reported feeling strongly attached to one or both adoptive parents. As children of self-giving parents, they have grown up to be more self-giving and altruistic than average (Sharma et al., 1998). Many scored higher than their biological parents and raised-apart biological siblings on intelligence tests, and most grew into happier and more stable adults (Kendler et al., 2015b; van IJzendoorn et al., 2005).

The apparent advantages of growing up adopted.

Those who are troubled by an apparent conflict between scientific and religious accounts of human origins may find it helpful to consider that different perspectives of life can be complementary. For example, the scientific account attempts to tell us when and how; religious creation stories usually aim to tell about an ultimate who and why. As Galileo explained to the Grand Duchess Christina, "The Bible teaches how to go to heaven, not how the heavens go."

The conflict between Science & Religion.

Although normal stimulation during the early years is critical, the brain's development does not end with childhood. Thanks to the brain's amazing plasticity, our neural tissue is ever changing and reorganizing in response to new experiences. New neurons are also born.

The continuous development of the brain.

In many modern cultures, gender roles are merging. Brute strength has become less important for power and status (think "philanthrocapitalists" Priscilla Chan and Mark Zuckerberg). From 1965 to 2016, women soared from 9 percent to 47 percent of U.S. medical students (AAMC, 2014, 2016). In 1965, U.S. married women devoted eight times as many hours to housework as did their husbands; by 2012, this gap had shrunk to less than twice as many (Parker & Wang, 2013; Sayer, 2016). Such swift changes signal that biology does not fix gender roles.

The continuous evolution of gender roles.

Research reveals that nature and nurture together shape our development—every step of the way.

The correlation of Nature & Nurture.

Same fertilized egg, same genes; different eggs, different genes Identical twins develop from a single fertilized egg, fraternal twins from two.

The difference between identical and fraternal twins.

Yet in personality measures, shared environmental influences from the womb onward typically account for less than 10 percent of children's differences. In the words of behavior geneticists Robert Plomin and Denise Daniels (1987; Plomin, 2011), "Two children in the same family are [apart from their shared genes] as different from one another as are pairs of children selected randomly from the population." To developmental psychologist Sandra Scarr (1993), this implied that "parents should be given less credit for kids who turn out great and blamed less for kids who don't." So, knowing that children's personalities are not easily sculpted by parental nurture, perhaps parents can relax and love their children for who they are.

The effects of parenting on personality.

Laboratory experiments confirm a gender difference in aggression. Men have been more willing to blast people with what they believed was intense and prolonged noise (Bushman et al., 2007). And outside the laboratory, men—worldwide—commit more violent crime (Antonaccio et al., 2011; Caddick & Porter, 2012; Frisell et al., 2012). They also take the lead in hunting, fighting, warring, and supporting war (Liddle et al., 2012; Wood & Eagly, 2002, 2007).

The gender difference in aggression.

Today, experts generally recommend postponing surgery until a child's naturally developing physical appearance and gender identity become clear. The bottom line: "Sex matters," concluded the National Academy of Sciences (2001). Sex-related genes and physiology "result in behavioral and cognitive differences between males and females."

The importance of sexual development.

National stereotypes exaggerate differences that, although real, are modest: Australians see themselves as outgoing. German-speaking Swiss see themselves as conscientious. And Canadians see themselves as agreeable. Actually, compared with the person-to-person differences within groups, between-group differences are small.

The minute nature of differences across cultures.

Among our similarities, the most important—the behavioral hallmark of our species—is our enormous adaptive capacity.

The most important human similarity.

Identical twins not only share the same genetic predispositions, they also seek and create similar experiences that express their shared genes (Kandler et al., 2012). This helps explain why identical twins raised in different families have recalled their parents' warmth as remarkably similar—almost as similar as if they had been raised by the same parents (Plomin et al., 1988, 1991, 1994). Fraternal twins have more differing recollections of their early family life—even if raised in the same family! "Children experience us as different parents, depending on their own qualities," noted Sandra Scarr (1990)

The parental experiences of children.

As we develop, we play, mate, and partner with peers. No wonder children and youths are so sensitive and responsive to peer influences.

The power of peer influence.

Nature selects behaviors that increase genetic success.

The principal of Sexual preferences.- Evolutionary Psychology

So great are the effects that, shown brief video clips of rats, you could tell from their activity and curiosity whether their environment had been impoverished or enriched (Renner & Renner, 1993). After 60 days in the enriched environment, the rats' brain weights increased 7 to 10 percent, and the number of synapses mushroomed by about 20 percent (Kolb & Whishaw, 1998). The enriched environment literally increased brainpower.

The result of an enriched environment on the brain.

Nature and nurture interact to sculpt our synapses.

The result of the interaction between nature & nurture.

We are the product of nature and nurture, but we are also an open system (FIGURE 12.7). Genes are all-pervasive but not all-powerful. People may reject their evolutionary role as transmitters of genes and choose not to reproduce. Culture, too, is all-pervasive but not all-powerful. People may defy peer pressures and resist social expectations.

The rigidity of nature & nurture.

Biology does not dictate gender. But in two ways, biology influences gender: Genetically—males and females have differing sex chromosomes. Physiologically—males and females have differing concentrations of sex hormones, which trigger other anatomical differences.

The ways in which biology influence gender.

Meanwhile, many people of science are awestruck at the emerging understanding of the universe and the human creature. It boggles the mind—the entire universe popping out of a point some 14 billion years ago, and instantly inflating to cosmological size. Had the energy of this Big Bang been the tiniest bit less, the universe would have collapsed back on itself. Had it been the tiniest bit more, the result would have been a soup too thin to support life. Astronomer Sir Martin Rees has described Just Six Numbers (1999), any one of which, if changed ever so slightly, would produce a cosmos in which life could not exist. Had gravity been a tad stronger or weaker, or had the weight of a carbon proton been a wee bit different, our universe just wouldn't have worked.

The wonder of the universe.

Like biological creatures, cultures vary and compete for resources, and thus evolve over time (Mesoudi, 2009).

Time's effect on culture.

Even as 5- to 12-year-olds, transgender children typically view themselves in terms of their expressed gender rather than their birth-designated sex (Olson et al., 2015b). From childhood onward, a person may feel like a male in a female body, or a female in a male body. Biologist Robert Sapolsky (2015) explains: "It's not that [these] individuals think they are a different gender than they actually are. It's that they [are] stuck with bodies that are a different gender from who they actually are."

Transgenders explained.

Riding along with a unified culture is like biking with the wind: As it carries us along, we hardly notice it is there. When we try biking against the wind we feel its force. Face-to-face with a different culture, we become aware of the cultural winds.

Variations in culture described.

In the United States there is a wide gulf between scientific and lay thinking about evolution.) "The idea that human minds are the product of evolution is . . . unassailable fact," declared a 2007 editorial in Nature, a leading science journal. In The Language of God, Human Genome Project director Francis Collins (2006, pp. 141, 146), a self-described evangelical Christian, compiled the "utterly compelling" evidence that led him to conclude that Darwin's big idea is "unquestionably correct." Yet Gallup pollsters have reported that 42 percent of U.S. adults believe that humans were created "pretty much in their present form" within the last 10,000 years (Newport, 2014). Many people who dispute the scientific story worry that a science of behavior (and evolutionary science in particular) will destroy our sense of the beauty, mystery, and spiritual significance of the human creature. For those concerned, we offer some reassuring thoughts.

The fear of contemporary science's destruction of the mysterious.

Neither heredity nor experience acts alone. Environments trigger gene activity. And our genetically influenced traits evoke significant responses in others. Thus, a child's impulsivity and aggression may evoke an angry response from a parent or teacher, who reacts warmly to well-behaved children in the family or classroom. In such cases, the child's nature and the parents' nurture interact. Gene and scene dance together.

Nature via nurture & nurture via nature explained.

Six weeks after you were conceived, you and someone of the other sex looked much the same. Then, as your genes kicked in, your biological sex—determined by your twenty-third pair of chromosomes (the two sex chromosomes)—became more apparent. Whether you are male or female, your mother's contribution to that chromosome pair was an X chromosome. From your father, you received the 1 chromosome out of 46 that is not unisex—either another X chromosome, making you female, or a Y chromosome, making you male. About seven weeks after conception, a single gene on the Y chromosome throws a master switch, which triggers the testes to develop and to produce testosterone, the main androgen (male hormone) that promotes male sex organ development. (Females also have testosterone, but less of it.)

Prenatal sexual development.

So as members of different ethnic and cultural groups, we may differ in surface ways. But as members of one species we are subject to the same psychological forces. Our outward reactions vary, yet our basic emotions are universal. Our tastes vary, yet they reflect common principles of hunger. Our social behaviors vary, yet they reflect pervasive principles of human influence. Cross-cultural research helps us appreciate both our cultural diversity and our human similarity.

Proportion of cultural similarities to differences.

ANSWER: Researchers use twin and adoption studies to understand how much variation among individuals is due to genetic makeup and how much is due to environmental factors. Some studies compare the traits and behaviors of identical twins (same genes) and fraternal twins (different genes, as in any two siblings). They also compare adopted children with their adoptive and biological parents. Some studies compare traits and behaviors of twins raised together or separately.

RP-2 How do researchers use twin and adoption studies to learn about psychological principles?

ANSWER: (1) It starts with an effect and works backward to propose an explanation. (2) This explanation may overlook the effects of cultural expectations and socialization. (3) Men could use such explanations to rationalize irresponsible behavior toward women.

RP-3 What are the three main criticisms of the evolutionary explanation of human sexuality?

ANSWER: Gender roles are social rules or norms for accepted and expected female and male behaviors. The norms associated with various roles, including gender roles, vary widely in different cultural contexts, which is proof that we are able to learn and adapt to the social demands of different environments.

RP-5 What are gender roles, and what do their variations tell us about our human capacity for learning and adaptation?

ANSWER: The biopsychosocial approach considers all the factors that influence our individual development: biological factors (including evolution and our genes, hormones, and brain), psychological factors (including our experiences, beliefs, feelings, and expectations), and social-cultural factors (including parental and peer influences, cultural individualism or collectivism, and gender norms).

RP-6 How does the biopsychosocial approach explain our individual development?

Girls prepared for menarche usually view it as a positive life transition (Chang et al., 2009). Males report mostly positive emotional reactions to spermarche (Fuller & Downs, 1990).

Reactions to the Puberty landmarks.

For many people, biological sex and gender coexist in harmony. Biology draws the outline, and culture paints the details. The physical traits that define a newborn as male or female are the same worldwide. But the gender traits that define how men (or boys) and women (or girls) should act, interact, or feel about themselves differ across time and place (Zentner & Eagly, 2015).

Sex & gender across cultures.

Scans of more than 1400 brains show no striking sex differences: "Human brains cannot be categorized into two distinct classes—male brain/female brain" (Joel et al., 2015).

Sex differences in the human brain.

Transgender people may be sexually attracted to people of the other gender, the same gender, both genders, or to no one at all.

Sexual orientation of transgenders.

Men pair widely; women pair wisely.

Sexual preferences in a nutshell.- - Evolutionary Psychology

And what traits do straight men find desirable? Some, such as a woman's smooth skin and youthful shape, cross place and time, and they convey health and fertility (Buss, 1994). Mating with such women might increase a man's chances of sending his genes into the future. And sure enough, men feel most attracted to women whose waist is roughly a third narrower than their hips—a sign of future fertility (Lewis et al., 2015; Perilloux et al., 2010). Even blind men show this preference for women with a low waist-to-hip ratio (Karremans et al., 2010). Men are most attracted to women whose ages in the ancestral past (when ovulation began later than today) would be associated with peak fertility (Kenrick et al., 2009). Thus, teen boys are most excited by a woman several years older than themselves, mid-twenties men prefer women around their own age, and older men prefer younger women.

Sexual preferences of heterosexual men.- Evolutionary Psychology

But humans in varied cultures nevertheless share some basic moral ideas. Even before they can walk, babies prefer helpful people over naughty ones (Hamlin et al., 2011). Worldwide, people prize honesty, fairness, and kindness (McGrath, 2015).

Shared moral ides across culture.

Whether male or female, each of us receives 23 chromosomes from our mother and 23 from our father. Of those 46 chromosomes, 45 are unisex—the same for males and females. Our similar biology helped our evolutionary ancestors face similar adaptive challenges. Both men and women needed to survive, reproduce, and avoid predators, and so today we are in most ways alike. Survival for both men and women involved traveling long distances, and in today's ultramarathons men and women are similarly competitive. Identify yourself as male or female and you give no clues to your vocabulary, happiness, or ability to see, learn, and remember. Males and females, on average, have comparable creativity and intelligence and feel the same emotions and longings (Hyde, 2014). Our "opposite" sex is, in reality, our very similar sex.

Similarities between males and females.

Are genetically identical twins also behaviorally more similar than fraternal twins? Studies of thousands of twin pairs in Germany, Australia, and the United States have found that identical twins are much more alike in extraversion (outgoingness) and neuroticism (emotional instability) than are fraternal twins (Kandler, 2011; Laceulle et al., 2011; Loehlin, 2012).

Similarities in identical twins compared to fraternal twins.

Regardless of our culture, we humans are more alike than different. We share the same life cycle. We speak to our infants in similar ways and respond similarly to their coos and cries (Bornstein et al., 1992a,b).

Similarities in varying cultures.

Twin researchers have replied that separated fraternal twins do not exhibit similarities comparable to those of separated identical twins.

Similarities of separated Fraternal twins compared to separated identical twins.

Males tend to be independent. Even as children, males typically form large play groups that brim with activity and competition, with little intimate discussion (Rose & Rudolph, 2006). As adults, men enjoy side-by-side activities, and their conversations often focus on problem solving (Tannen, 1990; Wright, 1989).

Social connectedness in males.

When searching for understanding from someone who will share their worries and hurts, people usually turn to women. Both men and women have reported that their friendships with women are more intimate, enjoyable, and nurturing (Kuttler et al., 1999; Rubin, 1985; Sapadin, 1988). Bonds and feelings of support are stronger among women than among men (Rossi & Rossi, 1993). Women's ties—as mothers, daughters, sisters, aunts, and grandmothers—bind families together. As friends, women talk more often and more openly (Berndt, 1992; Dindia & Allen, 1992). "Perhaps because of [women's] greater desire for intimacy," reported Joyce Benenson and colleagues (2009), first-year college and university women are twice as likely as men to change roommates. And how do they cope with stress? Compared with men, women are more likely to turn to others for support. They are said to tend and befriend (Tamres et al., 2002; Taylor, 2002)

Social connectedness of women vs men.

The formative nurture that conspires with nature begins at conception, with the prenatal environment in the womb, where embryos receive differing nutrition and varying levels of exposure to toxic agents. Nurture then continues outside the womb, where our early experiences foster brain development.

The beginning of nurture.

Transgender people may attempt to align their outward appearance and everyday lives with their internal gender identity. Brain scans reveal that those who seek medical sex-reassignment have some neural tracts that differ from those whose gender identity matches their birth-designated sex (Kranz et al., 2014; Van Kesteren et al., 1997).

The brain of some transgender individuals.

Genetically speaking, every other human is nearly your identical twin. Human genome researchers have discovered a common sequence within human DNA. This shared genetic profile is what makes us humans, rather than tulips, bananas, or chimpanzees.

The close genetic relation of humans.

Indeed, one of the big take-home findings of today's behavior genetics is that there is no single smart gene, gay (or straight) gene, or schizophrenia gene. Rather, our differing traits are influenced by "many genes of small effect" (Okbay et al., 2016; Plomin et al., 2016). Most of our traits have complex genetic roots.

The complexity of traits.

Other animals exhibit smaller kernels of culture. Chimpanzees sometimes invent customs—using leaves to clean their bodies, slapping branches to get attention, and doing a "rain dance" by slowly displaying themselves at the start of rain—and pass them on to their peers and offspring (Whiten et al., 1999). Culture supports survival and reproduction by transmitting learned behaviors that give a group an edge. But human culture does more.

The culture of Chimpanzees.

What caused this almost-too-good-to-be-true, finely tuned universe? Why is there something rather than nothing? How did it come to be, in the words of Harvard-Smithsonian astrophysicist Owen Gingerich (1999), "so extraordinarily right, that it seemed the universe had been expressly designed to produce intelligent, sentient beings"? On such matters, a humble, awed, scientific silence is appropriate, suggested philosopher Ludwig Wittgenstein: "Whereof one cannot speak, thereof one must be silent" (1922, p. 189).

The design of the universe.

In most countries, it's not easy being transgender. In a national survey of lesbian, gay, bisexual, and transgender Americans, 71 percent saw "some" or "a lot" of social acceptance for gay men, and 85 percent said the same for lesbians. But only 18 percent saw similar acceptance for transgender people (Sandstrom, 2015), who number about 1.4 million in the United States (Flores et al., 2016). And that is the experience of transgender people—46 percent of whom, in a survey of 27,175 transgender Americans, reported being verbally harassed in the last year (James et al., 2016). The psychiatric profession no longer considers gender nonconformity as a mental disorder, and thus no longer labels transgender people as having a "gender identity disorder." But some transgender people (not surprisingly, given the social disapproval) may experience profound distress and be diagnosed with gender dysphoria.

The difficulty of being transgender.

Child-raising practices reflect not only individual values, but also cultural values that vary across time and place. Should children be independent or obedient? If you live in a Westernized culture, you likely prefer independence. "You are responsible for yourself," families and schools tell their children. "Follow your conscience. Be true to yourself. Discover your gifts." Some Western parents go further, telling their children, "You are more special than other children" (Brummelman et al., 2015). (Not surprisingly, these children tend to have inflated self-views years later.) In the past, Western cultural values placed greater priority on obedience, respect, and sensitivity to others (Alwin, 1990; Remley, 1988). "Be true to your traditions," parents then taught their children. "Be loyal to your heritage and country. Show respect toward your parents and other superiors." Cultures change.

The effects of culture on child raising.

As empowered people generally do, men value freedom and self-reliance, which may help explain why men of all ages, worldwide, are less religious and pray less (Benson, 1992; Stark, 2002). Men also dominate the ranks of professional skeptics. All 10 winners and 14 runners-up on the Skeptical Inquirer list of outstanding twentieth-century rationalist skeptics were men. The Science and the Paranormal section of the 2010 Prometheus Books catalog (from the leading publisher of skepticism) included 98 male and 4 female authors. Women are far more likely to author books on spirituality.

The male mentality.

As cultures evolve, some trends weaken and others grow stronger. Individualism and independence have been fostered by voluntary emigration, a capitalist economy, and a sparsely populated, challenging environment (Kitayama et al., 2009, 2010; Varnum et al., 2010). In Western cultures, individualism has increased strikingly over the last century, following closely on the heels of increasing affluence (Grossmann & Varnum, 2015). This trend reached a new high in 2013 and 2014, when U.S. high school and college students reported increased tolerance, but also the greatest-ever interest in obtaining benefits for themselves and the lowest-ever willingness to donate to charity (Twenge, 2016; Twenge et al., 2012).

The perpetuation of individualism.

Parents do matter. But parenting wields its largest effects at the extremes: the abused children who become abusive, the deeply loved but firmly handled who become self-confident and socially competent.

The extremes of Parenting.

The power of the family environment also appears in the remarkable academic and vocational successes of many children of people who leave their home countries, such as those of refugees who fled war-torn Vietnam and Cambodia—successes attributed to close knit, supportive, even demanding families (Caplan et al., 1992).

The familial environment's effect on upbringing.

Why do women tend to be choosier than men when selecting sexual partners? Women have more at stake. To send her genes into the future, a woman must—at a minimum—conceive and protect a fetus growing inside her body for up to nine months. No surprise then, that heterosexual women prefer partners who will offer their joint offspring support and protection: stick-around dads over likely cads. Heterosexual women are attracted to tall men with slim waists and broad shoulders—all signs of reproductive success (Mautz et al., 2013). And they prefer men who seem mature, dominant, bold, and affluent (Conroy-Beam et al., 2015; Fales et al., 2016; Lukaszewski et al., 2016).

The sexual preferences of heterosexual women. - Evolutionary Psychology

Across cultures, we differ. But beneath differences is our great similarity—our capacity for culture. Culture transmits the customs and beliefs that enable us to communicate, to exchange money for things, to play, to eat, and to drive with agreed-upon rules and without crashing into one another.

The similarity of differing cultures.

By puberty, this pruning process results in a massive loss of unemployed connections. Here at the juncture of nurture and nature is the biological reality of early childhood learning. During early childhood—while excess connections are still on call—youngsters can most easily master such skills as the grammar and accent of another language. Lacking any exposure to language before adolescence, a person will never master any language. Likewise, lacking visual experience during the early years, a person whose vision is later restored by cataract removal will never achieve normal perceptions (Gregory, 1978; Wiesel, 1982). Without that early visual stimulation, the brain cells normally assigned to vision will die or be diverted to other uses. The maturing brain's rule: Use it or lose it.

Brain maturation.

Moreover, we cannot excuse our failings by blaming them solely on bad genes or bad influences. In reality, we are both creatures and creators of our worlds. So many things about us—including our gender roles—are the products of our genes and environments. Yet the stream that runs into the future flows through our present choices. Our decisions today design our environments tomorrow. The human environment is not like the weather—something that just happens. We are its architects. Our hopes, goals, and expectations influence our destiny. And that is what enables cultures to vary and to change. Mind matters.

Creators & creatures of our own worlds.

We see our adaptability in cultural variations among our beliefs and our values, in how we nurture our children and bury our dead, and in what we wear (or whether we wear anything at all). We are ever mindful that the worldwide readers of this book are culturally diverse. You and your ancestors reach from Australia to Africa and from Singapore to Sweden.

Culturally variation.

Cultures vary. Cultures change. And cultures shape our lives.

Culture in a nutshell.

Although Latino, Asian, Black, White, and Native Americans differ in school achievement and delinquency, the differences are "no more than skin deep." To the extent that family structure and economics, peer influences, and parental education predict behavior in one of these ethnic groups, they do so for the others as well.

Cultures are more similar than they are different.

Asian-Americans and European-Americans often differ in their parenting expectations. An Asian-American mother may push her children to do well, but usually not in a way that strains their relationship (Fu & Markus, 2014). Having a supportive "Tiger Mother"—one who pushes her children and works alongside them—tends to motivate children to work harder. European-Americans, however, might see this as pushy parenting that undermines children's motivation (Deal, 2011).

Differing parenting styles.

But our experiences also shape us. Our families and peer relationships teach us how to think and act. Differences initiated by our nature may be amplified by our nurture. If their genes and hormones predispose males to be more physically aggressive than females, culture can amplify this gender difference through norms that reward macho men and gentle women. If men are encouraged toward roles that demand physical power, and women toward more nurturing roles, each may act accordingly. Roles remake their players. Presidents in time become more presidential, servants more servile. Gender roles similarly shape us.

Experience and roles and the shaping of an individual.

Developing neural connections prepare our brain for thought, language, and other later experiences. So how do early experiences leave their fingerprints in the brain? Mark Rosenzweig, David Krech, and their colleagues (1962) opened a window on that process when they raised some young rats in solitary confinement and others in a communal playground. When they later analyzed the rats' brains, those who died with the most toys had won. The rats living in the enriched environment, which simulated a natural environment, usually developed a heavier and thicker brain cortex.

Experiences & brain development.

Gender differences in both social connectedness and power are greatest in late adolescence and early adulthood—the prime years for dating and mating. By their teen years, girls become less assertive and more flirtatious, and boys appear more dominant and less expressive (Chaplin, 2015). In adulthood, after the birth of a first child, attitude and behavior differences often peak. Mothers especially may become more traditional (Ferriman et al., 2009; Katz-Wise et al., 2010). By age 50, most parenting-related gender differences subside. Men become less domineering and more empathic, and women—especially those with paid employment—become more assertive and self-confident (Kasen et al., 2006; Maccoby, 1998). Worldwide, fewer women than men work full-time for an employer (19 percent versus 33 percent), but are similarly more satisfied with their lives when employed rather than unemployed (Ryan, 2016).

Gender differences throughout young life.

Take a minute to check your own gender expectations. Would you agree that "When jobs are scarce, men should have more rights to a job"? In the United States, Britain, and Spain, barely over 12 percent of adults agree. In Nigeria, Pakistan, and India, about 80 percent of adults agree (Pew, 2010). We're all human, but my, how our views differ. Northern European countries offer the greatest gender equity, Middle Eastern and North African countries the least (UN, 2015a).

Gender equity.

Your sexual orientation, as some say, is who you fantasize going to bed with; your gender identity is who you go to bed as.

Gender identity vs sexual orientation.

A gender role describes how others expect us to think, feel, and act. Our gender identity is our personal sense of being male, female, or, occasionally, some combination of the two.

Gender role vs gender identity.

Nomadic societies of food-gathering people have had little division of labor by sex. Boys and girls receive much the same upbringing. In agricultural societies, where women typically work in the nearby fields and men roam while herding livestock, cultures have shaped children to assume more distinct gender roles (Segall et al., 1990; Van Leeuwen, 1978).

Gender roles in Nomadic societies.

Once children grasp that two sorts of people exist—and that they are of one of these two sorts—they search for clues about gender. In every culture, people communicate their gender in many ways. Their gender expression drops hints not only in their language but also in their clothing, interests, and possessions. Having picked up such clues, 3-year-olds may divide the human world in half. They will then like their own kind better and seek them out for play. "Girls," they may decide, are the ones who watch My Little Pony and have long hair. "Boys" watch Transformers and don't wear dresses. Armed with their newly collected "proof," they then adjust their behaviors to fit their concept of gender. These stereotypes are most rigid at about age 5 or 6. If the new neighbor is a girl, a 6-year-old boy may assume he cannot share her interests. For young children, gender looms large.

Gender views of young children.

A question: What do you think of people who willingly change their behavior to suit different people and situations? People in individualist countries (the United States and Brazil), typically describe them as "dishonest," "untrustworthy," and "insincere" (Levine, 2016). In traditionally collectivist countries (China, India, and Nepal), people more often describe them as "mature," "honest," "trustworthy," and "sincere."

Individualism vs collectivism.

Even differences within a culture, such as those sometimes attributed to race, are often easily explained by an interaction between our biology and our culture.

Intercultural differences.

Accommodate to reality.

Coping method of Collectivism.

Change reality.

Coping method of Individualism.

RP-4 Match the following terms to the correct explanation. 1. Epigenetics 2. Molecular behavior genetics 3. Behavior genetics . a. Study of the relative effects of our genes and our environment on our behavior. b. Study of how the structure and function of specific genes interact with our environment to influence behavior. c. Study of environmental factors that affect how our genes are expressed.

ANSWER: 1. c, 2. b, 3. a

RP-3 Those studying the heritability of a trait try to determine how much of the person-to-person variation in that trait among members of a specific group is due to their differing __________.

ANSWER: genes

Altogether, you have some 20,000 genes, which are either active (expressed) or inactive.

Approximate number of genes.

Moreover, child neglect and abuse and even parental divorce are rare in adoptive homes. (Adoptive parents are carefully screened; biological parents are not.) So it is not surprising that, despite a somewhat greater risk of psychological disorder, most adopted children thrive, especially when adopted as infants (Loehlin et al., 2007; van IJzendoorn & Juffer, 2006; Wierzbicki, 1993).

Biological vs Adoptive parents on abuse and neglect.

A Russian scientist wondered how our human ancestors had domesticated dogs from their equally wild wolf forebears. Might he, within a comparatively short stretch of time, accomplish a similar feat by transforming the fearful fox into a friendly fox? To find out, Belyaev set to work with 30 male and 100 female foxes. From their offspring, he selected and mated the tamest 5 percent of males and 20 percent of females. (He measured tameness by the foxes' responses to attempts to feed, handle, and stroke them.) Over more than 30 generations of foxes, he and his successor repeated that simple procedure. Forty years and 45,000 foxes later, they had a new breed of foxes that, in the words of the successor (1999), were "docile, eager to please, and unmistakably domesticated. . . . Before our eyes, 'the Beast' has turned into 'beauty,' as the aggressive behavior of our herd's wild [ancestors] entirely disappeared."

Breeding Explanation and experiment. Dmitry Belyaev & successor Lyudmila Trut- Adaptation

. Animal-breeding experiments manipulate genetic selection.

Breeding simplified.- Adaptation.

Maintain connections, fit in, perform role.

Collectivism & Life task.

Few, close, and enduring; harmony is valued.

Collectivism & Relationships.

Us—group goals and solidarity; social responsibilities and relationships; family duty.

Collectivism & What matters.

Interdependent (identity from belonging to groups).

Collectivism & self.

A third criticism focuses on the social consequences of accepting an evolutionary explanation. Are heterosexual men truly hardwired to have sex with any woman who approaches them? If so, does it mean that men have no moral responsibility to remain faithful to their partners? Does this explanation excuse men's sexual aggression—"boys will be boys"—because of our evolutionary history?

Critiquing of Evolutionary Psychology.

Critics note that evolutionary psychologists start with an effect—in this case, the survey result showing that men were more likely to accept casual sex offers—and work backward to explain what happened. What if research showed the opposite effect? If men refused an offer for casual sex, might we not reason that men who partner with one woman for life make better fathers, whose children more often survive?

Critiquing of Evolutionary Psychology.

Evolutionary psychologists agree that much of who we are is not hardwired. "Evolution forcefully rejects a genetic determinism," insisted one research team (Confer et al., 2010). Genes are not destiny. And evolutionary psychologists remind us that men and women, having faced similar adaptive problems, are far more alike than different. Natural selection has prepared us to be flexible. We, humans, have a great capacity for learning and social progress. We adjust and respond to varied environments. We adapt and survive, whether we live in the Arctic or the desert.

Critiquing of Evolutionary Psychology.

Other critics ask why we should try to explain today's behavior based on decisions our distant ancestors made thousands of years ago. Don't cultural expectations also bend the genders? Alice Eagly and Wendy Wood (1999; Eagly, 2009) point to the smaller behavioral differences between men and women in cultures with greater gender equality. Such critics believe that social learning theory offers a better, more immediate explanation for these results. We all learn social scripts—our culture's guide to how people should act in certain situations. By watching and imitating others in their culture, women may learn that sexual encounters with strangers can be dangerous, and that casual sex may not offer much sexual pleasure (Conley, 2011). This alternative explanation of the study's effects proposes that women react to sexual encounters in ways that their modern culture teaches them. And men's reactions may reflect their learned social scripts: "Real men" take advantage of every opportunity to have sex.

Critiquing of Evolutionary Psychology.

As this exhibit at San Diego's Museum of Man illustrates, children learn their culture. A baby's foot can step into any culture.

Culture is learned.

The nucleus of every human cell contains chromosomes, each of which is made up of two strands of DNA connected in a double helix.

DNA in cells.

Parents do help to transmit their culture's views on gender. In one analysis of 43 studies, parents with traditional gender views were more likely to have gender-typed children who shared their culture's expectations about how males and females should act (Tenenbaum & Leaper, 2002). When fathers share equally in housework, their daughters develop higher aspirations for work outside the home (Croft et al., 2014).

Effects of parenting on gender.

Many gender similarities and differences transcend sexual orientation. Compared with lesbians, gay men (like straight men) report more responsiveness to visual sexual stimuli, and more concern with their partner's physical attractiveness (Bailey et al., 1994; Doyle, 2005; Schmitt, 2007; Sprecher et al., 2013). Gay male couples also report having sex more often than do lesbian couples (Peplau & Fingerhut, 2007). And (also like straight men) gay men report more interest in uncommitted sex.

Gender similarities & sexual orientation.

If a mark instructs the cell to ignore any gene present in that DNA segment, those genes will be "turned off"—they will prevent the DNA from producing the proteins normally coded by that gene.

Epigenetic marks explained.

Genes are self-regulating. Rather than acting as blueprints that lead to the same result no matter the context, genes react.

Epigenetics explained.

"Things written in pen you can't change. That's DNA. Things written in pencil you can. That's epigenetics" (Reed, 2012).

Epigenetics vs DNA.

Having faced many similar challenges throughout history, males and females have adapted in similar ways: We eat the same foods, avoid the same dangers, and perceive, learn, and remember similarly. It is only in those domains where we have faced differing adaptive challenges—most obviously in behaviors related to reproduction—that we differ, say evolutionary psychologists.

Evolutionary differences & similarities between males & females- Evolutionary Psychology

In this experiment, someone posing as a stranger approached people of the other sex and remarked, "I have been noticing you around campus. I find you to be very attractive." The "stranger" then asked a question, which was sometimes "Would you go to bed with me tonight?" What percentage of men and women do you think agreed? An evolutionary explanation of sexuality would predict that women would be choosier than men in selecting their sexual partners. In fact, not a single woman agreed—but 70 percent of the men did.

Experiment used to critique Evolutionary Psychology.

Note that gender identity is distinct from sexual orientation (the direction of one's sexual attraction).

Gender identity and sexual orientation.

Environmental events "turn on" genes, rather like hot water enabling a teabag to express its flavor. When turned on, genes provide the code for creating protein molecules, our body's building blocks.

Gene Activation.

Genes are DNA segments that, when expressed (turned on) direct the development of proteins that influence a person's individual development.

Genes described.

The genetic effect appears in physiological differences. Anxious, inhibited infants have high and variable heart rates and a reactive nervous system. When facing new or strange situations, they become more physiologically aroused (Kagan & Snidman, 2004; Roque et al., 2012).

Genetics in temperament.

Me—personal achievement and fulfillment; rights and liberties; self-esteem.

Individualism & What matters.

Independent (identity from individual traits).

Individualism & self.

Indeed, "with few exceptions anywhere in the world," reported cross-cultural psychologist Marshall Segall and his colleagues (1990, p. 244), "males are more likely than females to initiate sexual activity."

Largest sexuality difference bewteen males & females.

Natural selection is nature selecting traits and appetites that contribute to survival and reproduction. Evolutionary psychologists use this principle to explain how men and women differ more in the bedroom than in the boardroom. Our natural yearnings, they say, are our genes' way of reproducing themselves. "Humans are living fossils—collections of mechanisms produced by prior selection pressures" (Buss, 1995).

Natural selection and sex.- Evolutionary Psychology

Does the same process work with naturally occurring selection? Does natural selection explain our human tendencies? Nature has indeed selected advantageous variations from the new gene combinations produced at each human conception plus the mutations (random errors in gene replication) that sometimes result. But the tight genetic leash that predisposes a dog's retrieving, a cat's pouncing, or a bird's nesting is looser on humans. The genes selected during our ancestral history provide more than a long leash; they give us a great capacity to learn and therefore to adapt to life in varied environments, from the tundra to the jungle. Genes and experience together wire the brain. Our adaptive flexibility in responding to different environments contributes to our fitness—our ability to survive and reproduce.

Natural selection vs Adaptation in humans.

As an adoptive parent, I [ND] especially find it heartening to know that parents do influence their children's attitudes, values, manners, politics, and faith (Kandler & Riemann, 2013). Parenting—and the cultural environments in which parents place children—matters!

Parental influences on adopted children.

Similarly successful were those whose mating helped them produce and nurture offspring. Over generations, the genes of individuals not disposed to mate or nurture tended to be lost from the human gene pool. As success-enhancing genes continued to be selected, behavioral tendencies and learning capacities emerged that prepared our Stone Age ancestors to survive, reproduce, and send their genes into the future, and into you.

Perpetuating the shared human genome.

Identical twins, more than fraternal twins, look alike. So, do people's responses to their looks account for their similarities? No. In a clever approach, this researcher (and twin) compared personality similarity between identical twins and unrelated look-alike pairs. Only the identical twins reported similar personalities.

Personality similarities in twins. Nancy Segal (2013; Segal et al., 2013)

This evolutionary psychologist (2002, p. 73) noted that thanks to human evolution, our shared human traits—our emotions, drives, and reasoning—"have a common logic across cultures."

Steven Pinker (2002) on the Commonality of human Traits.

As inheritors of this prehistoric legacy, we are genetically predisposed to behave in ways that promoted our ancestors' surviving and reproducing. But in some ways, we are biologically prepared for a world that no longer exists. We love the taste of sweets and fats, nutrients that prepared our physically active ancestors to survive food shortages. But few of us now hunt and gather our food; instead, we find sweets and fats in fast-food outlets and vending machines. Our natural dispositions, rooted deep in history, are mismatched with today's junk-food and often inactive lifestyle.

The Prehistoric shared human genome today.

Later, during the fourth and fifth prenatal months, sex hormones bathe the fetal brain and influence its wiring. Different patterns for males and females develop under the influence of the male's greater testosterone and the female's ovarian hormones (Hines, 2004; Udry, 2000). If, however, females are prenatally exposed to unusually high levels of male hormones, they tend to grow up with more male-typical activity interests (Endendijk et al., 2016). Prenatal hormones help sculpt what we love to do.

The effects of prenatal hormones on later life.

In just a thin slice of history, gender roles worldwide have undergone an extreme makeover. At the beginning of the twentieth century, only one country in the world—New Zealand—granted women the right to vote (Briscoe, 1997). By 2015, all countries granted that right. A century ago, American women could not vote in national elections, serve in the military, or divorce a husband without cause. And if a woman worked for pay, she would more likely have been a midwife or a seamstress than a surgeon or a college professor. Now, more U.S. women than men graduate from college, and nearly half the workforce is female (DOL, 2015). In the STEM fields (Science, Technology, Engineering, and Mathematics), men currently hold most faculty positions (Ceci et al., 2014; Sheltzer & Smith, 2014). But when researchers invited U.S. professors to recommend candidates for STEM positions, most said they preferred hiring the highly qualified women over the equally qualified men (Williams & Ceci, 2015). The modern economy has produced jobs that rely not on brute strength but on social intelligence, open communication, and the ability to sit still and focus (Rosin, 2010).

The evolution of gender roles.

Aided by media publicity, this researcher and his colleagues located and studied 74 pairs of identical twins raised apart. They continued to find similarities not only of tastes and physical attributes but also of personality, abilities, attitudes, interests and even fears.

The similarities of separated identical twins.- Bouchard (2009)

At a genetic level, humans and chimpanzees are 96 percent identical (Mikkelsen et al., 2005). At "functionally important" DNA sites, this number reaches 99.4 percent (Wildman et al., 2003)! Yet that wee 0.6 percent difference matters. It took a human, Shakespeare, to do what a chimpanzee cannot—intricately weave 17,677 words into literary masterpieces.

The small difference between Humans and chimpanzees.

As young children, we were "gender detectives" (Martin & Ruble, 2004). Before our first birthday, we knew the difference between a male and female voice or face (Martin et al., 2002). After we turned 2, language forced us to label the world in terms of gender. English classifies people as he and she. Other languages classify objects as masculine ("le train") or feminine ("la table").

Young gender detectives.