The Scientific Objectivity of Gender Difference
- Post by: Glenn T. Stanton
- January 24, 2016
New Mother: What is it?
Obstetrician: I think it’s a bit early to be imposing roles on it now, don’t you think?
Monty Python, “The Meaning of Life”
Even the most aloof spectator of current culture cannot miss that the nature of gender and sex difference are white-hot issues today. They have been for quite some while actually, starting with the super hip and nouveau 1970s parental conviction that so-called “gender neutral” toys would create more sensitive, compassionate, non-judgmental children.
How did that work out? These parents were aghast to see Suzy feed her dump truck its bottle, wrap it up nice and cozy, and put it down for its nap. Johnny turned his kitchen set’s broom and mop into swords and rifles with which to vanquish the bad guys. Such actions baffled these free-thinking parents, because they knew they did not teach these things to their kids, and also knew they did not learn them at the homes of their friends or at their Montessori schools. Totally confounded, these parents saw such stereotypes emerge from their sweet children’s own nature as boys or girls. This tempered some of their ideological conviction that gender difference is taught, merely a cultural construct: Remove the stereotypes, and you free your children from the gendered behavior. These parents came to realize that some stereotypes are stereotypes for a reason, but that realization has not kept new generations of parents from trying the same thing with their kids.
As the revolution against the acceptance of an inherent and intrinsic human male and female nature continues to this day, it ironically does so against the tide not only of basic human experience, but an impressive and growing body of sophisticated emerging science as well. These facts reveal that the prevailing “cultural construct” theory of gender is more rooted in ideology than actuality.
We will ask and seek to answer two questions in this examination: First, is there an objective and humanly/culturally universal male and female nature? And second, how do we know?
The answer to the first question: There most certainly is. We know this because of the breakthroughs in two very interesting fields of scientific inquiry: one is the hard science of neurobiology and the other is the softer science of cultural anthropology and evolutionary psychology. Let us first examine the findings of neurobiology from the last two decades or so.
The Case from Neurobiology
Two of the earliest experts to write on this issue were the British team of geneticist Anne Moir and science journalist David Jessel in their groundbreaking book Brain Sex, which looks at how sex difference is not just seen in clothing fashion choices or sex organs, but in the very brain and neural wiring of the human person. Based on their own work and that of others, Moir and Jessel explain with equal parts boldness, clarity, and sureness:
. . . The truth is that virtually every professional scientist and researcher into the subject has concluded that the brains of men and women are different. . . . [T]he nature and cause of brain differences are now known beyond speculation, beyond prejudice, and beyond reasonable doubt.
As a result, “There has seldom been a greater divide between what intelligent, enlightened opinion presumes—that men and women have the same brain—and what sciences knows—that they do not.” Therefore, they proclaim in frankness, “It is time to cease the vain contention that men and women are created the same. They were not and no amount of idealism or Utopian fantasy can alter that fact.”
Professor Alice Eagly from Northwestern University, a major contributor to the field of the social psychology of gender difference, also distinguishes between elite assumption and scientific findings.
. . . [T]he majority of [studies] have conformed in a general way to people’s ideas about the sexes. . . this evidence suggests that lay people, once maligned in much feminist writing as misguided holders of gender stereotypes, may be fairly sophisticated observers of female and male behaviour.
To be clear, Eagly is referring supportively to our grandmothers who never went in for the new-fangled ideas of today.
Of course, the nature of male and female brain differences have wide-ranging differences for the whole person. Leading neuropsychiatrist Louanne Brizendine, working from the University of California San Francisco, explains that while male and female, as human beings, are certainly more similar than they are alike—we share a common and equal humanity of course—our seemingly small neurological and genetic differences create substantial and significant differences in the two sexes:
More than 99 percent of male and female genetic coding is exactly the same. Out of the thirty thousand genes in the human genome, the less than one percent variation between the sexes is small. But that percentage difference influences every single cell in our bodies—from the nerves that register pleasure and pain to neurons that transmit perception, thoughts, feelings and emotions. (emphasis added)
Simon Baron-Cohen, professor of Developmental Psychopathology at the University of Cambridge, outlines a great many important and primary contrasts between the female and male mind in his deeply researched book The Essential Difference. From his first lines, Baron-Cohen is frank with his reader:
The subject of essential sex differences in the mind is clearly very delicate. I could tiptoe around it, but my guess is that you would like the theory of the book stated plainly. So here it is: The female brain is predominantly hard-wired for empathy. The male brain is predominantly hard-wired for understanding and building systems.
The Anthropological and Evolutionary Psychological Record
It is not only the physiological, neural, and hormonal aspects of the human being that demonstrate clear and indisputable gender differences. Being rooted in the minutest parts of our physical make-up, of course these things work themselves out in the ways males and females act, carry and conduct themselves in daily life, their general personalities as well as their preferences in mate selection and sexual mores. This has become well and very interestingly documented in a growing body of multi-cultural anthropological investigations, largely by evolutionary psychologists. Let us examine a fair sampling of their most illuminating findings derived from examinations of developed, developing, and under-developed countries throughout the world on every continent as well as a robust sampling of individual and far-ranging island cultures.
First, scientists find that the tasks and activities performed interchangeably by male and female across all distinct human cultures range generally from 0 to 35 percent of general human activity. The rest of the general daily tasks in the family and community or village are gender distinct. While some of this division of labor is indeed different from culture to culture, there are also significant and consistent universal similarities as well. Two leading scholars on this topic explain:
The cross-cultural literature provides strong evidence of the universality of a sex-typed division of labour . . . Although few activities [such as trapping, hunting, metal, stone and wood working, fowling, care for the exterior of the home, etc. and primary child-care, care for the inside of the home, gathering vegetal foods, dairy production, spinning and clothes care, cooking and water supply, etc.] are assigned exclusively to one sex or the other when considered across cultures, the division of labor is evident in that, within societies, most activities were performed primarily by one sex [or the other].
In only one percent of societies are the tasks of gathering the necessary resources of subsistence performed more by the woman than the man. These scholars favor the evolutionary biosocial theory in understanding these distinctions, explaining “that biology, social structure, and the environment interact reciprocally to produce the sex-typed roles” of men and women in the home and community.
Social structure certainly plays a role in shaping sex- and gender-distinct differences between male and female according to these scholars, but only a part. It does not, by itself, shape social roles nor create additional genders.
Another universal feature of sex-specific social organization across cultures is found in the ways parents and extended family guide both boys and girls in “sex-appropriate” play and behavior as they grow in their personal and social development. The universal commonalities we find here are what allow even an unobservant or uneducated member of one culture to go anywhere in the world and easily discern which members of that community are the women and girls and which are the men and the boys, apart from body shape. To be sure, across cultures, girls generally resemble the women in hundreds of different ways as the boys resemble the men. No male or females (young or adult) possess or demonstrate all the same types and mix of masculine or feminine characteristics and qualities, but there is a universal essence that is undeniable.
In a very interesting course of study, evolutionary psychologists have observed sex differences in sexual interests, mate selection, and romantic desires in more than 60 different cultures. The answers to the following questions should be fairly obviously: Which gender is more likely to report feelings of guilt and being used following casual sex with different partners, even when reporting they weren’t mistreated or lied to in the experience? Who shows more approval of, and interest in, casual sex? Regarding early sexual fantasies, who is far more likely to say their fantasies were initiated “in response to visual stimulus”? Who is far more likely to report their fantasies developed or occurred in the context of “a real or imagined romantic relationship”? Forty-five percent of which gender (compared to six percent of the other) reported they had sexual fantasies “many times a day”? Thirty-five percent of which gender said they had such fantasies “only once a week” (compared to only eight percent of the other)? Which gender’s fantasies were more sexually explicit, focused on body parts and numerous partners? Which gender’s fantasies were more focused on “commitment and romance”? Who finds infidelity more hurtful and gets more jealous of perceived outside romantic interests? Who has a sex-drive that is more consistent from week to week? Who is more interested in mating with someone older? Who is more interested in mating with someone younger? These are some of the questions scholars stuied across cultures.
If men and women are essentially the same, this little quiz might be tricky for you. But it wasn’t, was it? The correct answer to each question, according to the research, is precisely what you most likely guessed. In fact, there is only one question where male and female are essentially the same across cultures and that has to do with jealousy and hurt feelings related to the infidelity of their partner. Men and women are the same in this regard, but markedly different in all the others.
Is There a Male or Female Personality?
Do male and female demonstrate different personalities in how they live, view their lives, and interact with others? If so, how distinct are these differences? And how reliable is the research? The answers to these questions, in order, are “absolutely,” “considerable,” and “quite.”
A handful of teams for various universities have studied what they call the “Big Five Personality Traits” across more than fifty different cultures and determined gender-distinct qualities and characteristics that are largely universal from culture to culture. One group of scholars explain: “gender differences are modest in magnitude” but “consistent with gender stereotypes, and replicable across cultures.” Some examples are:
- Universally, men rank substantially higher in assertiveness and women much higher in nurturance.
- Women are more likely to exhibit fearful emotions and anxious concern as well as desires to improve family situations and conditions.
- Men are typically more adventurous, excited, and willing to take risks and move out into new areas. They are also more overtly influential in terms of leadership.
- Women are consistently more affectionate and sentimental.
- Women are most interested and concerned about life events and situations in closer proximity to them.
- Men are more likely to be interested and concerned with events and situations beyond the village.
- Where women see danger and concern, men see challenges.
In addition, the personality inventories revealed that men work more in the mental arena of ideas and women more in the emotional arena of feelings and intuition. Both are essential.
Professor Alan Feingold, working from Yale and one of the early scholars to survey and summarize the growing body of research on gender-distinct personality differences across diverse cultures, explains that these differences have remained largely consistent both through generations and across nations. His findings indicate “a strong biological basis” for these gender-distinct personality traits.While social influences are certainly active in creating gender differences, science finds there is a natural and universal male and female nature that drives such differences as well.
In addition, there are strong and consistent findings pertaining to vocational interests: men are more likely engaged in investigative, explorative, and building interests, while women rank higher in a variety of artistic, care-giving, and relational interests. Men tend to like to build things. Women tend to like to make things. The seemingly subtle differences between these are generally understood by men and women. While the customer populations at Home Depot and Hobby Lobby are certainly not gender segregated, they certainly are heavily gender weighted. One way of being is no more important than the other. Human culture requires both.
Another study in this body of literature took an interesting turn. In collecting data throughout fifty cultures on six continents, some researchers decided to go beyond what the data-collectors found in their fieldwork. They wanted to examine how these scientific and methodical maleandfemale data-collectors themselves differed in their judgments and interpretations of findings from their subjects.
Even though there was an objectiveness and form to the data being collected, these investigators found that their female data-collectors were, more so than men, less critical of their subjects and more likely to describe them in positive ways. The women focused and reported more on positive personality qualities like gregariousness, warmth, trustworthiness, and altruism. These, according to theory, reflect a greater relational interest among women. The men were more focused on the facts of things—the task at hand—with very little intuitive perception about the people being interviewed.
Following is a quick run-down of many curious, more esoteric, and lesser known male/female differences documented across cultures in this research literature:
- Women tend to smile more often than men.
- Both men and women prefer to look at female bodies rather than male bodies.
- Women tend to be more positive in their assessments of other people than are men.
- Females make up more than 90 percent of all anorexia and bulimia sufferers.
- Men have stronger self-confidence about their appearance regardless of what others think of the way they look.
- Men’s ideal female body shape is heavier than what women assume it is.
- Females attempt suicide more often than males.
- Males succeed at suicide far more often than females, and their suicides are more violent.
- Boys tend to have higher athletic confidence and self-esteem than girls.
- Generally, girls tend to perform better academically and receive better grades than boys, but their academic self-esteem is similar.
- Men are generally more assertive, more inclined to take chances, and more open to ideas.
- Women are more tender-minded, agreeable, warm, and open to feelings.
- Women tend to show higher levels of life-satisfaction compared to men.
Some of these measures were double for one gender than for the other.
When Genders Are Free to Be
Similar research is also uncovering fascinating information that is counterintuitive to the twenty-first-century mind.
Given that cultures are different and that male and female differences are demonstrated to varying degrees in different cultures, where would you imagine gender differences between male and female to be most pronounced?
In traditional, developing cultures, where men and women have to depend on each other for daily survival, where today’s food is collected, prepared, cooked, and consumed today?
Or . . .
In modern cultures that are more technologically, economically and politically advanced, where men and women have the resources and cultural freedoms to become and do what they desire?
It appears that when they enjoy greater freedom—financially, politically, and culturally—men become more stereotypically masculine and women more stereotypically feminine. This is, however, most true for women.
The New York Times summarized the findings of personality tests in more than 60 different countries and cultures: “It looks as if personality differences between men and women are smaller in traditional cultures like India’s or Zimbabwe’s than in the Netherlands or the United States.” The New York Times concludes: “The more Venus and Mars have equal rights and similar jobs, the more their personalities seem to diverge.”
This research was led by David P. Schmitt, director of the International Sexuality Description Project. He observes that as wealthy modern nations remove the old barriers between men and women, “some ancient internal differences are being revived.” According to these findings, when men and women have the opportunity—provided by greater education, financial recourses, and political and cultural freedom—to move beyond traditional gender expectations and roles to become whatever they want to be, they actually become even more distinctly masculine or feminine if even in some seemingly non-traditional ways.
As well, The New York Times reported that gender differences in personalities were greater across the more gender-equitable North America and Europe than across the less gender-equitable Asia and Africa. This led these scholars generally to favor a biological basis for gender difference over cultural construction, because when culture allowed for more freedom and opportunities, the gender distinctions became more pronounced. Earlier research in 2001 and as early as 1990 arrived at essentially the same conclusion: In more developed, individualistic, progressive, and egalitarian countries, gender differences don’t shrink, but instead become conspicuously magnified.
Professor Schmitt concludes: “An accumulating body of evidence, including the current data, provides reason to question social role explanations of gender and personality development.”
Social Construction and Nature/Biology
So many findings from cutting-edge research reveal “social construction” as the primary reason for gender difference to have little substance. It exists primarily in the minds of the gender-theory folks and those who take their beliefs as truth.
It is interesting to note how robustly science disproves the overly ambitious and confident claims of social-construction gender theory. In the mid-1970s, psychology professor Lois Hoffman boldly proclaimed, “Adult sex roles are converging, and therefore sex differences among children and future generations of adults can be expected to diminish.”
Contrast her statement with a 2001 finding from a major literature survey on sex-typing (the way that gender difference is understood and exhibited), which found:
Taken overall, a substantial body of research reveals a very clear picture: in spite of widespread expectations and desires, the various aspects of gender differentiation are not disappearing, if anything there is an increase in sex-typing, especially with the pattern most expected to decline, the femininity of females. (emphasis added)
This increasing perception of femininity among women was strongest among women themselves, with both sexes recognizing this increase. The researchers conclude, “There is no evidence of change toward a more androgynous personality for either sex.” (emphasis original)
The consistency of differences—and the kinds of differences—in males and females as evidenced in cross-cultural studies provides strong support for the idea that these “stereotypes” of male and female are more deeply rooted in biology than in culture. As the study just cited found, “the findings of this and other research . . . are not consistent with the sociocultural explanation of gender difference. They are consistent with the evolutionary model.”
More recent writings report the same: “The weight of the empirical evidence, including cross-cultural findings by researchers who have no vested interest in any particular theoretical stance, robustly confirms these evolutionary-based predictions.” As well, “These findings are difficult to reconcile with the gender similarities hypothesis . . . ”
One of the primary reasons that males have become more masculine and females more feminine is in their sheer psychic and emotional comfort in being so. People in more prosperous countries are voting with their resources and freedoms and becoming more “stereotypically” gender distinct. Mate attraction also plays an important role. As finding a good man or woman as a mate gets more difficult because of rising expectations and busy schedules, both men and women are becoming more gender-distinct in their mate-attracting efforts. Their advertising gets more vivid, if you will, not because they are forced to, but because they want to. They know what is more likely to get the desired results.
One of the primary reasons that the idea of any differences between male and female are so strongly resisted today is that many equate difference with inferiority and superiority. Women are different from men, therefore they must be weaker. This is a remarkably wild and unfortunate leap in reasoning. We do not come to such a conclusion in other parts of life where things are different. Italian food is different from sushi. A vacation in the mountains is different from one at the seashore. But we do not assume that one of these is better than the other because they are different. Both have their own distinct qualities that simultaneously make each better than the other in different ways at different times in different situations.
Alice Eagly shows that the political and social consequences of marking the differences between male and female do not fall harder on the females. In a journal article entitled “The Science and Politics of Comparing Women and Men,” Eagly explains that in dealing in male and female stereotypes, “the stereotypes of women [are] more positive overall than the stereotype of men, at least in contemporary samples of U.S. and Canadian college students.” She adds that when examined, the literature on gender difference indeed “do not tell a simple tale of female inferiority.” It is not a small point to note that she is writing here in the early to mid-nineties, examining earlier records in a time when we were less mindful of avoiding gender stereotypes in academic work.
The Importance of Gender-Distinct Parents
If one is going to hold to a gender-construction theory of gender difference, or that male and female are only different in the bedroom or bathroom, it must be done either in ignorance or denial of a mountain of impressive anthropological, psychological, and neurological scientific research that reveals the opposite.
It is actually personal and social androgyny that is a social construct, for it only exists within the rickety ideological scaffolding of gender studies theory. It must be built and sustained with great intention, ideological force, and political power.
This belief can lead us to some very dangerous results. Male and female matter for society, first and foremost because they are essential to the family. Just as male and female are different kinds of human beings, mothers and fathers are different kinds of parents, bringing different things to the irreplaceable task of parenting that both boys and girls need. The family as a universal, pan-historical fundamental is inherently gendered for many reasons.
The literature on the importance of fathers for healthy child development explores this well, and is so convincing that it compelled the Clinton, Bush, and Obama administrations to each develop robust father involvement programs. And few dare doubt the importance of mothers for healthy and happy child development. What are some of the ways that mothers and fathers as gender-distinct parents contribute different but necessary things to healthy child development? Let us look at just a few examples by developmental life stage.
Notice young parents and notice how fathers and mothers interact differently with their infant. Who is more likely to get the child giggling wildly and physically excited and active? Fathers have been shown to be more physically stimulating, unpredictable, and rousing with their babies than are mothers. Mothers tend to be more soothing, comforting, and quieting. One study shows us that 70 percent of father/infant play is very physical and active, while only 4 percent of mother/infant play tends to be this way. In fact, one study showed that when given the choice, two-and-a-half year olds were more likely to gravitate toward father as a play partner compared to mom because of his manner of play. Children need both mom’s and dad’s way of play.
As our children start exploring the world, they need at least two things: safety from dangerous situations and encouragement to explore in safe ways. Mothers are masters at keeping children safe. Fathers, while they do not care for the well-being of their children any less, are more inclined to teach their children to have new experiences and to do so confidently. Father’s way is more likely to experience scrapes and bruises. It is the rare father who warns, “I don’t think he’s ready for that yet!”
Consider something each of sees quite often, regardless of where in the world we come from: tossing babies in the air. This is actually an important development experience. When the children go up, they unmistakably have a look of great terror on their face. The toss literally takes their breath away. But as physics does its thing, as sure as they go up, they come down. As they reconnect with the strong arms and hands that tossed them, nearly to a child, what happens? If the child is verbal, he or she says “Again!” with great excitement. They love it, and there is a whole industry built on this thrilling experience: amusement parks. In the up and down of this throw, the child learns the world can be a scary place. When they come back down into safe hands, they learn they can depend on others to be there for them. This builds confidence and the stimulation to take reasonable risks, to be willing to swim away from the dock a bit in life. But we must ask, who do we see tossing babies the most? It’s not mom or grandma. It’s daddy, grandpa, or Uncle Bob. Men throw babies.
As the kids grow older, close your eyes at the playground and listen to the parents there. Who is more likely to say, “Climb up to the next branch!” “You can do it!” “Run a bit faster!” or “Try jumping off from there—I’ll catch you!”? From whom are you more likely to hear “Be careful!” “Slow down!” “Not so high!” or “Don’t go so far!”? Both moms and dads will say any of these things to be sure, but one is far more likely to say them. They are not gender neutral!
Also consider language development. Scholars studying such things tell us that mothers and fathers communicate differently with their children. Mother’s way of communicating with her children creates a quicker, easier connection. She knows how to connect with the child on his or her level. Fathers are less likely to moderate their vocabulary for their children. They use bigger words, not because they are smarter than mom, but because they are just not as mindful of what their children do or do not understand. Mom’s way facilitates immediate communication and understanding. Dad’s way often facilitates a vocabulary lesson. Both are necessary and beneficial.
This is also true of non-verbal communication. Fathers are more likely to communicate through sounds, grunts, and facial expression. Children are more likely to experience a disapproving “ehh!” or an I’m-thinking-about-it “ummm” from dad than mom. Children, particularly girls, who will experience these things in the adult world from male coaches and bosses, will be more comfortable and confident in interacting with and responding to such communication and not be hurt, confused, or intimidated by it.
Consider as well the development of motor skills. As fathers tend to be more physical and exerting, they are more likely to help their boys and girls develop their large motor skills: throwing, catching, balancing, climbing, hammering, jumping. Mothers are more likely to help develop fine motor skills: drawing, cutting, coloring, sewing, painting, gluing, braiding. Again, certainly these differences are not gender absolute, but we do find that mothers are more likely to teach their children one set of things and fathers others.
Fathers and mothers make important contributions in adolescence as well, when children are learning to navigate the world more independently. Fathers are more likely to work at preparing their children for the challenges and dangers of the world, while mothers are more interested in and better at protecting them from the dangers of the world. Both have the child’s best interest in mind, but they go about it in different ways. Consider a lightning storm or vicious dog in the neighborhood. Mom’s direction is short and sweet: stay away. Period. Dad does not encourage his children to seek out such things, but he realizes such challenges are out there and wants to make sure his child knows the safest thing to do when these dangerous situations might present themselves.
Consider our children’s developing sexuality as well, a key part of healthy human development. Girls who are well loved and cared for by a good, safe father are not as likely to fall for the lame advances of immature boys. Girls who do not have this in a father are indeed much more likely to fall for such a boy because they so desperately want to know what it feels like to be important to a male. Hence, it is no surprise that girls growing up in fatherless homes are dramatically more likely to become pregnant before marriage.
A boy who grows up with a good dad also learns how to demonstrate and display his masculinity in healthier, pro-social ways. He is not as likely to be physically violent or dominating. He does not have as much of a need to prove himself, because his father has already given him this confirmation and acceptance. He is not as likely to be a “player” sexually because he has learned from his father how properly to treat and respect a lady. His sister also witnesses this healthy male behavior and learns that she will not settle for less.
Moms and dads are not just necessary for the creation of new life. They are just as essential for the development of that life into full, healthy masculinity and femininity. There are obviously single parents who have done remarkable work in raising their children to be respected and desirable community leaders. But these parents, nearly to a person, will tell us that if they could have had it any other way, they would have preferred to have their child’s other parent alongside in a healthy, loving manner. Few think “alone” is inherently better or even equal. As we observe parenting around the world, throughout history, we see the necessity of mothers and fathers as a human universal. It is only in the present age, in the last few nano-seconds of human history, that we have assumed that mothers and fathers are only needed if the adults in the family desire them.
Such a belief is contrary to a very diverse body of honest, empirical science as well as basic daily human experience. This will become more evident to us, and contribute to a larger and more convincing body of research literature, after we try to raise a generation of children in the current and untested experiment of the gender theorists.
Glenn T. Stanton is the director of Global Family Formation Studies at Focus on the Family and a research fellow at the Institute of Marriage and Family in Ottawa, Ontario. He has written many books on the subjects of marriage and family. This essay is adapted from a presentation originally given at World Congress of Families IX, October 27-30, in Salt Lake City, Utah.
 The author realizes that many gender theorists make a distinction between what sex and gender are. He rejects the notion that this distinction is based in any objective discovery or reality, but is rather theory recently developed out of ideology.
 Anne Moir and David Jessel, Brain Sex: The Real Difference Between Male and Female (New York: Dell Publishing, 1991), 8, 9, 11.
 Alice Eagly, “On Comparing Men and Women,” Feminism and Psychology 4 (1994): 513-22.
 Louanne Brizendine, The Female Brain (New York: Broadway Books, 2006), 1.
 Simon Baron-Cohen, The Essential Difference (New York: Basic Books, 2003), 1.
 Wendy Wood and Alice H. Eagly, “A Cross-Cultural Analysis of the Behavior of Women and Men: Implications for the Origins of Sex Difference,” Psychological Bulletin 128 (2002): 699–727, at 705.
 Ibid., 705.
 Ibid., 718.
 Todd Shackelford, David P. Schmitt, and David M. Buss, “Universal Dimensions of Human Mate Preference,” Personality and Individual Differences 39 (2005): 447–58; Paul Okami and Todd K. Shackelford, “Human Differences in Sexual Psychology and Behavior,” Annual Review of Sex Research 12 (2001): 186–241; David P. Schmitt, “Sociosexuality from Argentina to Zimbabwe: A 48-Nation Study of Sex, Culture, and Strategies of Human Mating,” Behavioral and Brain Sciences 28 (2005): 247–311; David P. Schmitt (and 118 members of the International Sexuality Description Project), “Universal Sex Differences in the Desire for Sexual Variety: Tests From 52 Nations, 6 Continents, and 13 Islands,” Journal of Personality and Social Psychology 85 (2003):85–104; Emily Stone, et al., “Sex Differences and Similarities in Preferred Mating Arrangements,” Sexualities, Evolution and Gender 7 (2005): 269–276.
 Both men and women show the same levels of jealousy in response to a partner’s infidelity, but exhibit this in different ways and for different situations. Women’s anger and jealousy increases if the relationship is emotionally strong, rather than merely physical. For men, there is no difference between emotional and non-emotional infidelity.
 Paul Costa, Antonio Terracciano, and Robert R. McCrae, “Gender Differences in Personality Traits Across Cultures: Robust and Surprising Findings,” Journal of Personality and Social Psychology 81 (2001): 322–31, at 328.
 Alan Feingold, “Gender Differences in Personality: A Meta-Analysis,” Psychological Bulletin 116 (1994): 429–46, at 449, 430.
 Robert McCrae, Antonio Terracciano and 78 Members of the Personality Profiles in Culture Project, “Universal Features of Personality Traits from the Observer’s Perspective: Data from 50 Cultures,” Journal of Personality and Social Psychology 88 (2005): 547–61.
 David P. Schmitt et al., “Why Can’t a Man Be More Like a Woman? Sex Differences in Big Five Personality Traits Across 55 Cultures,” Journal of Personality and Social Psychology 94 (2008): 168-82; Brittany Gentile et al., “Gender Differences in Domain-Specific Self-Esteem: A Meta-Analysis,” Review of General Psychology 13 (2009): 34–45.
 Gentile, et al., “Gender Differences in Domain-Specific Self-Esteem.”
 John Tierney, “As Barriers Disappear, Some Gender Gaps Widen,” New York Times, September 9, 2008.
 Robert R. McCrae, “Universal Features of Personality Traits From the Observer’s Perspective: Data From 50 Cultures,” Journal of Personality and Social Psychology 88 (2005), 547-61.
 John E. Williams and Deborah L. Best, Sex and Psyche: Gender and Self Viewed Cross-Culturally (Newbury Park: Sage, 1990); Costa et al., “Gender Differences in Personality Traits Across Cultures,” 329.
 Schmitt et al., “Why Can’t a Man Be More Like a Woman?” 178.
 Lois W. Hoffman, “Changes in Family Roles, Socialization and Sex Differences,” American Psychologist 32 (1977): 644–57, at 646.
 Lloyd B. Lueptow et al., “Social Change and The Persistence of Sex Typing: 1974–1997,” Social Forces 80 (2001): 1–35, at 16.
 Lueptow et al., “Social Change and The Persistence of Sex Typing: 1974–1997,” 19, 22.
 Ibid., 24.
 David M. Buss and David P. Schmidtt, “Evolutionary Psychology and Feminism,” Sex Roles 64 (2011) 768-87, at 783.
 Alice H. Eagly, “The Science and Politics of Comparing Women and Men,” American Psychologist 50(1995): 155.
 For example, see the research presented in David Popenoe, Life Without Father: Compelling Evidence that Fatherhood and Marriage are Indispensable for the Good of Children and Society (New York: Free Press, 1996); David Blankenhorn, Fatherless America: Confronting Our Nation’s Most Urgent Social Problem (New York: Basic Books, 1995); Kyle Pruett, Fatherneed: Why Father Care is as Essential as Mother Care for Your Child (New York: Free Press, 2000); Marcia J. Carlson, “Family Structure, Father Involvement and Adolescent Behavioral Outcomes,” Journal of Marriage and Family 68 (2006): 137-154; Ronald P. Rohner and Robert A. Veneziano, “The Importance of Father Love: History and Contemporary Evidence,” Review of General Psychology 5 (2001) 382-405; K. Allison Clarke-Stewart, “And Daddy Makes Three: The Father’s Impact on Mother and Young Child,” Child Development 49 (1978) 466-78; Michael E. Lamb, “Fathers: Forgotten Contributors to Child Development,” Human Development 18 (1975) 245-66.
 I address this question in book-length detail in Glenn T. Stanton, Secure Daughters Confident Sons: How Parents Guide Their Children into Authentic Masculinity and Femininity (Colorado Springs: Multnomah, 2011).
 Eleanor E. Maccoby, The Two Sexes: Growing Up Apart, Coming Together (Cambridge: Harvard University Press, 1999), 266.
 K. Allison Clarke-Stewart, “The Father’s Contribution to Children’s Cognitive and Social Development in Early Childhood,” in F.A. Pedersen, ed., The Father-Infant Relationship: Observational Studies in Family Setting (Santa Barbara: Praeger, 1980).
 Cf. Stanton, 171-3.
 David Popenoe, Life Without Father: Compelling Evidence that Fatherhood and Marriage are Indispensable for the Good of Children and Society (New York: The Free Press, 1996), 145.
 Maccoby, 267.
 Cf. Popenoe, 140; Stanton, 201-7.