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UNCORRECTED PROOF
1
Chapter 11
The Evolution of Culturally-Variable Sex
Differences: Men and Women Are Not Always
Different, but When They Are…It Appears
Not to Result from Patriarchy or Sex Role
Socialization
David P. Schmitt
© Springer International Publishing Switzerland 2014
T. K. Shackelford, R. D. Hansen (eds.), The Evolution of Sexuality, Evolutionary Psych olog y
DOI 10.1007/978-3-319-09384-0_11
D. P. Schmitt ()
Department of Psychology, Bradley University, 75 Bradley Hall, Peoria, IL 61625, USA
e-mail: dps@bradley.edu
Just like all other sexually reproducing species, male and female humans are more
similar than different. Even so, men’s and women’s psychological traits sometimes
differ in important ways, both in terms of typical or average levels (Buss 1989; Del
Giudice 2009; Ellis 2011) and in terms of variability (Archer and Mehdikhani 2003;
Borkenau et al. 2013; Lippa 2009). Sex differences in numerous traits have been
well-established as moderate to large in size1 and as culturally pervasive. For exam-
ple, sex differences in negative emotion-related traits have been documented across
several meta-analyses (Feingold 1994; Miettunen et al. 2007; Whissell 1996), inte-
grative neuroscientific reviews (Hyde et al. 2008; Stevens and Hamann 2012), and
large cross-cultural surveys (Costa et al. 2001; Hopcroft and McLaughlin 2012;
Lippa 2009; McCrae and Terracciano 2005; Schmitt et al. 2008; Van de Velde et al.
2010). Using a multivariate approach, Del Giudice et al. (2012) documented across
16 personality traits—ranging from dominance and liveliness to perfectionism and
tension—that sex differences in personality are astonishingly large, with only 10 %
overlap in men’s and women’s overall distributions.
Beyond sex differences in personality traits, psychologists have uncovered
dozens of ways that men and women differ in affect, behavior, and cognition
across most cultures (Archer 2014; Browne 1998; Mealey 2000). In one com-
prehensive review, Ellis (2011) identified 63 psychological sex differences that
have been replicated across multiple cultures and at least 10 studies, with not a
single replication failure (probably an overly strict exclusionary criterion; see
Schmitt et al. 2014). In another wide-ranging review, Archer (2014) reported cul-
turally-pervasive sex differences are reliably found in the assessment of negative
emotions (e.g., fear, anxiety, depression), anti-social behaviors (e.g., aggression,
violence, criminality), cognitive abilities (e.g., mental rotation, object location,
1 According to Cohen (1988), effect sizes expressed in terms of the d statistic are considered small
if 0.20, medium if 0.50, and large above 0.80.
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verbal fluency), personality traits (e.g., agreeableness, neuroticism, sociability),
motor activities (e.g., strength, throwing ability, activity level), sexual attitudes
and behaviors (e.g., mate preferences, sociosexuality, sexual coercion), and nu-
merous other characteristics such as interest in infants and occupations (see also,
Lippa 2005).
The pervasive nature of so many psychological sex differences necessitates se-
rious questions concerning the origin of men’s and women’s panculturally distinc-
tive psychologies (Brown 1991; Norenzayan and Heine 2005). Among the most
likely forces behind culturally ubiquitous sex differences include the specialized
design of men’s and women’s evolved psychological adaptations (Buss 1995;
Mealey 2000), universal features of human sex role socialization (which may be
generated, in part, by evolved features of gendered sexual psychology; see Mac-
coby 2000; Pirlott and Schmitt 2014; Williams and Best 1990), and a wide range
of other developmental and biocultural factors that produce the profoundly perva-
sive sex differences exhibited by our species (Geary 1998; Low 2000; Miller and
Halpern 2014).
Despite growing evidence that many sex differences are at least partially the
result of specially-designed differences in the evolved psychology of men and
women (Archer 2014; Buss and Schmitt 2011; Ellis 2011), many contemporary so-
cial scientists still assume—in accordance with the Standard Social Science Model
(SSSM; see Tooby and Cosmides 1992)—that men’s and women’s psychologi-
cal differences, if they exist at all (Hyde 2005), are solely the result of extensive
sex role socialization processes and sociopolitical power differentials (Eagly and
Wood 1999). As Wood and Eagly (2002) assert, “it is likely that extensive so-
cialization is required to orient boys and girls to function differently” (p. 705).
Given this blank slate approach to psychological sex differences, it is unsurprising
that social role theorists further assume that sex differences should be conspicu-
ously smaller in cultures with more egalitarian sex role socialization or greater
sociopolitical gender equity (e.g., greater representation of women in parliament;
see Kasser and Sharma 1999; Wood and Eagly 2002; Zentner and Mitura 2012).
Indeed, there can be no more ironclad prediction than the “demise of many sex
differences with increasing gender equality is a prediction of social role theory”
(Eagly et al. 2004, p. 289).
In this chapter, evidence is marshalled across 21 data sources that directly chal-
lenge this foundational assumption of social role theory and, more generally, the
SSSM. In fact, most psychological sex differences—in personality, sexuality, at-
titudes, and cognitive abilities—are conspicuously larger in cultures with more
egalitarian sex role socialization and greater sociopolitical gender equity. Even sex
differences in physical traits such as height, body mass index, obesity, and blood
pressure are larger in cultures with more egalitarian sex role socialization and great-
er sociopolitical gender equity (Schmitt et al. 2014). In order to explain these coun-
ter-intuitive patterns, it is helpful to understand four basic evolutionary perspectives
on the generation of psychological sex differences.
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11 The Evolution of Culturally-Variable Sex Differences…
Obligate Sex Differences: Culturally Insensitive
Sex-Specific Adaptations
There are four basic ways that evolved psychological adaptations generating sex
differences across cultures (see Fig. 11.1). The first is for men and women to be
adaptively designed to manifest relatively uniform sex differences across cultures.
Evolutionary theories such as Sexual Selection Theory (Darwin 1871) and Paren-
tal Investment Theory (Trivers 1972) suggest that, as mammals, men and women
likely pursue somewhat different mating strategies and at least some of the adaptive
design of men’s and women’s evolved mating psychologies will be robustly mani-
fested across cultures (Lippa 2005; Schmitt 2005a). According to Lippa (2009), sex
differences in sex drive demonstrate a particularly persistent and uniform magni-
tude across all cultures and are entirely unrelated to factors such as degree of sex
role socialization and sociopolitical gender equity. Much like human sex differences
in physical strength and stature (Deaner et al. 2012; Gaulin and Boster 1985; Puts
2010; Van Damme et al. 2008), it is not the case that all men must have higher
sex drives than all women for the sex difference to have resulted from evolved
psychological adaptations. Nor must evolved sex differences be present at birth, a
common misconception (Voyer et al. 2007; Wood and Eagly 2012). Instead, sex dif-
ferences in traits such as sex drive and physical strength likely result from obligate
sex-specific adaptations consistently generating, on average and to about the same
degree, observable sex differences across all cultural forms (or at least across all
cultures with similar ecologies; see also Baumeister et al. 2001).
According to the neuroandrogenic theory of psychological sex differences (Ellis
2001), a key mechanism that generates panculturally uniform sex differences is the
organizational effect of prenatal sex hormone exposure on the developing human
brain (see also Baron-Cohen 2004). In a sweeping review of the literature, Ellis
(2011) identified 63 psychological sex differences that are culturally universal and
likely result from human males (but not females) experiencing testosterone-related
brain masculinization between 12 and 22 weeks of gestation (Archer 2014; Baron-
Cohen 2002; Ellis 2011). It is not that all 63 sex differences—ranging from person-
ality traits to work preferences to consuming behavior—are immediately present at
birth. Instead, the prenatal masculinization (or not) of the human brain adaptively
biases the development of future psychological traits, particularly in terms of risk-
taking (Byrnes et al. 1999), sensation-seeking (Cross et al. 2011), and systematiz-
ing-versus-empathizing (Baron-Cohen 2004).
Supportive findings of this perspective on sex differences come from studies
of girls exposed to male-typical levels of testosterone in utero (compared to their
unaffected sisters) developing more male-typical personalities and play behaviors
(Alexander et al. 2009; Auyeung et al. 2009). Indeed, prenatal testosterone exposure
within normal levels also predicts sexually differentiated childhood behavior in girls
and boys (Hines 2006; Udry et al. 1995), including dose-dependent relationships
between degree of testosterone exposure and male-typical behavior (Nordenström
et al. 2002), results that are not explainable from measured degree of parental sex
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role socialization (Pasterski et al. 2005). Further support of neuroandrogenic theory
includes findings that girls with gene variants that make them more sensitive to
testosterone develop more masculine personalities (with especially strong effects
among those girls whose mothers tried the hardest to socialize their daughters to
Varying Levels of
Moderation
Obligate Evolved Sex Differences
Universal
Sex Differences
across
Evolved Sex Differences
in Psychology
(due to organizational,activational,
or direct genetic effects) Cultures
Facultatively-MediatedEvolved SexDifferences
Evolved Sex Differences
in Psychology Mediated
by Sex Differences
in Facultative Sensitivity to
Local Ecology
Emergently-ModeratedEvolved Sex Differences
Evolved Sex Differences
in Psychology Emerge as
Moderated by Other Adaptations
or Sociocultural Factors
(e.g., religion)
No Evolved Sex Differences: Social Role Theory
No Evolved
Sex Differences
in Psychology,
Just a Blank Slate
Varying Sex Role
Socialization
Varying Ecological
Conditions
Larger Sex
Differences
Smaller Sex
Differences
Larger Sex
Differences
Smaller Sex
Differences
Larger Sex
Differences
Smaller Sex
Differences
Fig. 11.1 Four approaches to evolved sex difference variation across cultures
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11 The Evolution of Culturally-Variable Sex Differences…
be highly feminine; Udry 2000) and studies that show gene variants and biomark-
ers linked to brain masculinization influence transsexualism in predictably ways in
adults (Hare et al. 2009; Schneider et al. 2006). In short, the seeds of many psycho-
logical sex differences appear to be sewn before birth, with future developmental
experiences being shaped by the degree of prenatal neuroandrogenic brain mascu-
linization (Alexander and Wilcox 2012).
Some psychological sex differences are not established before birth, of
course, and instead result from activational effects that emerge in early childhood
(Del Giudice and Belsky 2010; Ellis 2004) or at puberty (Galambos et al. 2009;
Hyde et al. 2008; Ruigrok et al. 2013). From a life history perspective (Kaplan
and Gangestad 2005), just as sex differences in body hair, muscle mass, and voice
pitch emerge most strongly at puberty (Puts 2010), many psychological sex differ-
ences may be designed to emerge most strongly with the onset of such factors as
ambulatory exploration (Silverman et al. 2007) or mating effort (Burke et al. 2014).
Other psychological sex differences may result from direct genetic effects in which
specific genes outside the sex chromosomes function differently in the brains of
men and women (Becker et al. 2007; McCarthy and Arnold 2011; Ngun et al. 2011;
Trabzuni et al. 2013).
Regardless, compared to the “ethnographic hyperspace” of all possible sexual
cultures one can imagine (Cronk 1999), it appears some psychological adaptations
in men and women are obligate enough to generate persistent and relatively uni-
form psychological sex differences across all cultures (Brown 1991; Gaulin 1997;
Karremans et al. 2010; Lippa 2010). Of course, even obligate sex differences are
not immutable, as there always exists a continuous interplay of biological and
environmental factors that can alter the degree of human sexual differentiation.
Sometimes the size of psychological sex differences is variable as a direct result
of specially-designed psychological adaptations. That is, sometimes evolution
generates culturally-variable sex differences by design.
Facultatively-Mediated Sex Differences: Differential
Sensitivity to Local Conditions
A second way evolution generating sex differences across cultures is for men and
women to be specially designed with differentially-sensitive facultative adapta-
tions. For instance, men’s and women’s adaptations may be specially designed to
be differentially sensitive to local ecological information. Sometimes men are adap-
tively designed to be more sensitive to ecological conditions, at other times women
are designed to be more sensitive (see Baumeister 2000; Ellis 2004; Schmitt 2011).
Critically, it is the differential sensitivity of men’s and women’s adaptations, com-
bined with varying local ecologies, that facultatively mediates variation in size or
degree of psychological sex differences across cultures (see Fig. 11.1).
The notion that evolved biology may be specially designed to anticipate that
ecological variability is a foundational component of phenotypic plasticity
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(Gomulkiewicz et al. 1995; Pigliucci 2001; Stearns and Koella 1986). Across spe-
cies, phenotypic plasticity has been implicated in strategies of predator avoidance,
physical polymorphisms, the timing of developmental experiences, and alternative
reproductive tactics (Kelly et al. 2012). For example, depending on the type of
plant a certain caterpillar feeds on, its physical structure changes to match its sur-
roundings (Whitman and Agrawal 2009). Similarly, some species of grasshopper
facultatively alter their color depending on local ecology. Grasshoppers in darker
ecologies grow a dark body, whereas grasshoppers in green ecologies grow a green
body (Burtt 1951). Any differences between green and dark grasshoppers are not
genetic differences; they represent the same genome facultatively responding in a
mediated way to ecological variation (Nettle 2009).
In humans, phenotypic plasticity (Hughes et al. 2003), Life History Theory
(Geary 2002; Kaplan and Gangestad 2005), and the related concept of “evoked
culture” (Tooby and Cosmides 1992) have generated a wealth of findings on the
adaptive effects of ecological variability on human psychology (Ellis et al. 2009;
Del et al. 2010; Griskevicius et al. 2011; Nettle 2009). For example, Gangestad
et al. (2006) has shown that both men’s and women’s long-term mate preference
adaptations for health, attractiveness, and intelligence in potential mates are facul-
tatively evoked in cultures with high pathogens. In the realm of mating adaptations,
local pathogen levels appear to facultatively mediating a culture’s level of polyg-
yny (Low 1990), fertility rate (Guégan et al. 2001), sociosexuality levels (Schaller
and Murray 2008), expressed mate preferences (DeBruine et al. 2010; Moore et al.
2013), and degree of parental care (Quinlan 2007).
In this view, human psychological adaptations may be built in a way that gener-
ates predictable patterns of cultural variability, but not in an agnostic blank slate
way. Instead, human psychological adaptations are designed to pay specific atten-
tion to particular sources of ecological information and generate specially designed,
highly functional, sex-specific forms of behavior (Gangestad and Simpson 2000;
Hartung 1985; Hill et al. 2014; Lancaster 1994; Marcinkowska et al. 2014; Schmitt
and Rohde 2013).
Schmitt et al. (2003) found that men are generally higher in dismissing
attachment and this sex difference is nearly universal across cultures, but not always
(Del Giudice 2011). Sex differences in dismissing attachment become negligible in
cultures with high ecological stress (such as having high pathogen levels), in part,
due to women’s psychology being specially-designed to be more sensitive to stress-
ful ecological contexts (see also Belsky 2012; Schmitt 2011). In other words, both
men’s and women’s attachment psychology reacts to stressful ecologies with great-
er dismissing attachment, but it is more adaptive for women’s “dismissing reaction”
psychology to respond more strongly. This greater sensitivity in women’s psychol-
ogy results in women’s dismissing attachment levels becoming nearly as high as
men’s in stressful ecological contexts. From a facultatively-mediated perspective,
human cultures—including the degree of sex differences in human cultures—can
be both evolved and variable.
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11 The Evolution of Culturally-Variable Sex Differences…
Emergently-Moderated Sex Differences:
On the Freedom to Express Sex-Specific Psychology
A third way evolution can generate psychological sex differences across cultures
for men and women to be adaptively designed to manifest psychological sex differ-
ences across cultures (in either obligate or facultative forms), but the full expres-
sion of those sex-specific adaptations is moderated by other factors (Massimini and
Delle Fave 2000). One example of emergently-moderated sex differences comes in
the form of biological suppression. Biological suppression involves the nondevel-
opment of an adaptation that is normally present in the species.
A prime instigator of adaptation suppression in humans may be the potent cul-
tural factor of religion. For example, the eighteenth century religious sect called the
Shakers abolished the practice marriage, insisted upon complete sexual celibacy,
and eradicated nearly all physical contact between men and women (Foster 1981).
As a consequence, the adaptive expression of most, if not all, evolved sex differenc-
es in mating psychology that was greatly suppressed in Shaker culture. Another po-
tent factor in the emergently-moderated suppression of sex differences is ecological
stress. For instance, although sex differences in height are largely obligate across
cultures, they can be emergently suppressed in cultures with especially poor nutri-
tion and extremely stressful ecological conditions (Guégan et al. 2000; Gustafsson
and Lindenfors 2008; Katzmarzyk and Leonard 1998; Nettle 2002). As Gaulin and
Boster (1992) noted in their review of sex differences in stature across 155 human
societies, “substandard nutrition could cause individuals to fall short of their geneti-
cally set growth potential, and, importantly, males seem to be more sensitive to such
developmental perturbations than females” (p. 474). Hence, in high stress ecologies
sex differences in height can be attenuated.
Another instance of emergently-moderated or suppressed sex differences comes
from the “mismatch” perspective in evolutionary psychology (Crawford 1998;
Nesse and Williams 1994). Evolutionary mismatch perspectives explain psycho-
logical variation across cultures by the degree of mismatch between contemporary
environmental conditions and those within which early humans evolved—namely,
hunter-gatherer environments (Brown 1991; Tooby and Cosmides 1990). When
contemporary environments are different from hunter–gatherer environments in
critical ways, the adaptive development of innate psychological sex differences can
be suppressed (Schmitt et al. 2008). It is also possible, though, for contemporary en-
vironments to accentuate evolved sex differences in an emergently-moderated way.
An illustrative example of the emergently-moderated sex differences approach can
be found in cross-cultural studies of human values. Schwartz and Rubel (2005) docu-
mented that most sex differences in expressed personal values emerge more strongly
in nations with egalitarian sex role socialization and greater sociopolitical gender eq-
uity. They note that men and women may have evolved sex differences in certain val-
ues (e.g., men’s mating psychology may have evolved to value power, achievement,
and hedonism more than women; whereas women’s tendency toward child-rearing
may have evolved to value benevolence and universalism more than men). They
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speculate that “Increased independence and equality of women in the labor force may
encourage them to express distinctive values rather than to accommodate their values
to those of their husbands” (p. 1023). In their view, it is possible that in cultures with
egalitarian sex role socialization and greater sociopolitical gender equity, men and
women are freer to express their evolved, sex-specific psychological adaptations. As
they noted in 2009, egalitarian sex role socialization and greater sociopolitical gender
equity could “permit both sexes to pursue more freely the values they inherently care
about more.” (Schwartz and Rubel-Lifshitz 2009, p. 171). It is not that humans are
adapted to anticipate this freedom and have special design features that facultatively
respond to it, instead it is the case that sex differences in values may be obligate (or
perhaps facultative) and the degree of psychological sex difference is an emergently-
moderated response this to freedom (see also, Barber 2014).
Noting differences between mediation and moderation effects has led to con-
ceptual advances in social psychology (Baron and Kenny 1986). A key concep-
tual difference between the facultatively-mediated adaptation approach and the
emergently-moderated approach outlined here is that the facultatively-mediated
approach views cultural variation in psychological sex differences as adaptive and
design-specific—facultative adaptations are designed to interact with only certain
ecological factors and to generate only certain functional outcomes. In contrast,
the emergently-moderated approach views cultural variation in psychological sex
differences as a domain-general byproduct of extraneous factors (Barber 2014).
It is possible these moderating extraneous factors involve evolved psychological
adaptations, such as adaptations for the generation of religion (Kirkpatrick 2011;
Weeden and Kurzban 2013). Moreover, there may be some factors that biologically
intensify, rather than suppress, psychological adaptations, such as religions intensi-
fying adaptions involving violence and sexuality (Keller 1990; Sela et al. 2014) and
bifurcated sex roles intensifying adaptations that normally generate merely small to
moderate psychological sex differences (see Pirlott and Schmitt 2014).
The key conceptual point is that the facultatively-mediated approach, but not the
emergently-moderated approach, views cross-cultural variation in sex differences
as resulting from adaptations specially-designed for properly generating those very
sex difference variabilities. In the emergently-moderated approach, cross-cultural
variation in sex differences is merely a functionally-disruptive side effect of some
other factor. Finally, there can exist combinations of these first three evolutionary
explanations of sex differences, such as obligate sex differences that are emergent-
ly-moderated in certain contexts (e.g., height differences suppressed by poor nutri-
tion), facultatively-mediated adaptations that are emergently-moderated in certain
contexts (e.g., mate preference differences suppressed by religion), and so forth.
For instance, although the variation appearing in local sex ratios is strongly associ-
ated with shifts in men’s and women’s sexuality (Guttentag and Secord 1983), it
remains unclear which sex differences in sexuality are facultatively versus emer-
gently responding to local sex ratios (Hudson and Den Boer 2004; Lazarus 2002;
Marlowe and Berbesque 2012; Pedersen 1991). Only by clearly specifying the pre-
cise mechanisms—obligate, facultative, and emergent—will researchers be able to
fully explain the connections between human sex ratio variation and psychological
sex differences.
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11 The Evolution of Culturally-Variable Sex Differences…
Social Role Theory: Sex Differences
Drawn on a Blank Slate
A fourth way psychological sex differences might be generated across cultures is
through domain-general learning combined with sex role socialization. According
to social role theory, most psychological sex differences result from exposure to sex
role socialization, a process whereby a culture defines and enforces the appropriate
ways of thinking, feeling, and behaving for men and women (Eagly 1987; Ruble
and Martin 1998). For some social role theorists, the motivated origin of these sex
roles primarily involves men’s patriarchal attempts to subjugate and control wom-
en (Dworkin 1987; MacKinnon 1982; Rudman et al. 2013) and the privileging of
men via androcentrism (Bem 1993). For others, evolved physical differences
between the sexes create pancultural divisions of labor which, in turn, generate
emergent sex roles (Alesina et al. 2013; Wood and Eagly 2002). Regardless, it is
assumed by social role theorists that sex roles are the most direct cause amongst all
observed psychological differences between men and women—with the only innate
psychology of men and women presumed, by default, to consist of a single blank-
slated domain-general learning mechanism (Katz 1995; Kitzinger 1994).
As a consequence, assuming that sex roles are the sole cause of sex differences,
social role theorists expect that when men and women occupy more similar roles,
sex differences will erode (Eagly and Wood 1999; Wood and Eagly 2002). With-
out extensive sex role socialization, in this view, there would be no observable
psychological sex differences. Indeed, Wood and Eagly (2002) have specifically
argued that “it is likely that extensive socialization is required to orient boys and
girls to function differently” (p. 705) and Eagly et al. (2004) have asserted the “de-
mise of many sex differences with increasing gender equality is a prediction of
social role theory” (p. 289). Thus, the social role approach unambiguously predicts
that psychological sex differences will be attenuated or even eliminated in cultures
with more egalitarian sex role socialization and greater sociopolitical gender equity
(Bem 1993).
Measuring Psychological Sex Differences, Sex Role
Socialization, and Sociopolitical Gender Equity Across
Cultures
Evaluating these four perspectives—obligate, facultative-mediation, emergent-
moderation, and social role—on how psychological sex differences vary (or not)
across cultures is the focus of this chapter. Utilizing findings on sex differences
across dozens of large cross-cultural studies, 21 sources of evidence are presented
suggesting psychological sex differences that can be simultaneously evolved and
variable across cultures. Moreover in most cases, evidence suggests counter-intui-
tively so that sex differences emerge more strongly in cultures with egalitarian sex
role socialization and greater sociopolitical gender equity.
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National indicators of sex role socialization and sociopolitical gender equity
come in two basic forms. First, there are many international organizations that rate
nations along dimensions related to sex role socialization and sociopolitical gender
equity (see Else-Quest and Grabe 2012; Hyde 2012). Perhaps the most commonly
used metric among this form estimating sociopolitical gender equality is the Gender
Empowerment Measure (GEM) of the United Nations (Wood and Eagly 2002). The
GEM is a composite index measuring gender inequality in three basic dimensions
of empowerment—economic participation and decision-making, political partici-
pation and decision-making, and power over economic resources. Also in this cat-
egory of national gender equity indicators are the Gender Gap Index of the World
Economic Forum, the Gender Gap Index of Social Watch, and the Standardized
Index of Gender Equality (SIGE; Dijkstra 2002).
The second basic type of indicator of sex role socialization and sociopolitical
gender equity comes from cross-cultural studies that provide direct assessments
of individual attitudes toward gender equality, women’s freedom, and women’s
place in family and work. Based on these individual responses, researchers gener-
ate overall national averages along gender equity-related dimensions. Examples of
this form of national gender equity include attitudes toward gender equality from
nationally-representative attitude surveys (Inglehart and Norris 2003), surveys of
hostile and benevolent sexism (Napier et al. 2010), and surveys of sex role ideology
(SRI; Schmitt et al. 2014). Schmitt et al. (2014) reported in a 58-nation study that
there are very high correlations among both type of measures, with the progressive
SRI correlating positively with both the United Nations’ GEM, r(56) = .65, p < .001,
and the nationally-representative indexes of gender equality attitudes (Inglehart and
Norris 2003), r(30) = .76, p < .001. In this chapter, reviewed findings will generally
refer to how national levels of psychological sex differences are related to both
types of indicators.
Evaluating Social Role Theory’s Ability to
Explain the Size of Sex Differences Across Cultures
According to the SSSM and various social role theories of sex differences, men’s
and women’s psychological differences are solely the result of extensive sex role
socialization processes and sociopolitical power differentials (Eagly et al. 2004;
Eagly and Wood 1999). As a result, social role theorists assume that sex differ-
ences should be conspicuously smaller in cultures with more egalitarian sex role so-
cialization or greater sociopolitical gender equity (Kasser and Sharma 1999; Wood
and Eagly 2002; Zentner and Mitura 2012). Several data sources are relevant for
evaluating this empirical claim, including sex differences in self-reported Big Five
personality traits.
Big Five Personality Traits Several studies have found pervasive sex differences in
Big Five personality traits, with women typically scoring higher in agreeableness
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11 The Evolution of Culturally-Variable Sex Differences…
and neuroticism (Feingold 1994). Social role theory predicts that sex differences
in all Big Five personality traits will be smaller in nations with more egalitarian
sex role socialization and greater sociopolitical gender equity. Several studies have
evaluated this prediction. In almost every instance, the observed pattern of sex dif-
ferences across cultures strongly disconfirms social role theory’s predictions.
For instance, in one of the earliest and largest studies of sex differences in per-
sonality across cultures, Costa, Terracciano, and McCrae (2001) found in most
countries women were higher on the extraversion facet of warmth, agreeableness,
neuroticism, and the openness facet of feelings, whereas men scored higher on
scales measuring the extraversion facet of assertiveness and the openness facet of
ideas (see also Lynn and Martin 1997; McCrae 2002; Weisberg et al. 2011). In direct
disconfirmation of social role theory, Costa et al. (2001) reported that sex differ-
ences in most Big Five personality traits were larger in egalitarian cultures where
women have more equal opportunities with men (McCrae 2002). Both in self-report
and other-report data, Asian and African cultures generally showed the smallest sex
differences, whereas European and American cultures—where the egalitarian sex
role socialization and sociopolitical gender equity indexes were generally higher—
showed the largest differences (McCrae and Terracciano 2005).
In 2008, Schmitt and his colleagues reported findings from a cross-cultural study
of sex differences across 55 nations of the International Sexuality Description Proj-
ect ( n = 17,637). Based on responses to the Big Five Inventory (Benet-Martínez and
John 1998), women reported higher levels of extraversion, agreeableness, conscien-
tiousness, and neuroticism than men across most nations. Overall, more egalitarian
sex role socialization and greater sociopolitical gender equity were associated with
larger sex differences in personality. The same pattern of findings also has been
replicated in a large cross-cultural study by Lippa (2009), further disconfirming sex
role theory.
In a study of 58 nations called the International Sexuality Description Project-2
(ISDP-2; Schmitt et al. 2014), data were collected from a more diverse set of cul-
tures than previous studies, including samples from several Northern European na-
tions with relatively high levels of gender egalitarianism (e.g., Denmark, Finland,
Iceland, and Norway) and several new samples from less egalitarian nations (e.g.,
Colombia, Ecuador, Nigeria, and Swaziland). Men’s and women’s nation-level
personality traits were related to Sex Role Ideology (SRI as directly measured in
the ISDP-2), an index of gender equality attitudes from a nationally-representa-
tive study (Inglehart and Norris 2003), the Standardized Index of Gender Equality
(SIGE), the Gender Empowerment Measure (GEM), and other indicators of sex role
socialization and sociopolitical gender equity across this more diverse set of na-
tions. Schmitt et al. (2014) reported across nearly all Big Five traits that egalitarian
sex role socialization and greater sociopolitical gender equity were associated with
larger sex differences in personality.
Overall, women generally score higher than men on measures of extraversion
(Schmitt et al. 2014). As noted in Table 11.1, increasing levels of egalitarian sex role
socialization and greater sociopolitical gender equity are generally associated with
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12 D. P. Schmitt
Trait Effects of increasing sociopolitical
gender equity on sex differences
across cultures
Social role prediction
Traits typically higher in women
Extraversion Gender equity increases extraver-
sion, more so in women—sex differ-
ences widen
Disconfirmed
Agreeableness Gender equity increases agreeable-
ness, more so in women—sex differ-
ences widen
Disconfirmed
Conscientiousness Gender equity increases conscien-
tiousness, more so in women—sex
differences widen
Disconfirmed
Neuroticism Gender equity decreases neuroti-
cism, more so in men—sex differ-
ences widen
Disconfirmed
Love Gender equity increases love, more
so in women—sex differences
widen
Disconfirmed
Resources mate preference Gender equity decreases preferences
for resources, more so in women—
sex differences narrow
Confirmed
Intimate partner violence Gender equity decreases intimate
partner violence, more so in men—
sex differences widen
Disconfirmed
Spatial location ability Gender equity increases spatial loca-
tion ability, more so in women—sex
differences widen
Disconfirmed
Crying Gender equity increases crying,
more so in women—sex differences
widen
Disconfirmed
Depression Gender equity decreases depression,
more so in men—sex differences
widen
Disconfirmed
Benevolence values Gender equity increases benevo-
lence values, more so in women—
sex differences widen
Disconfirmed
Empathetic occupation
preference
Gender equity unrelated to empa-
thetic occupation preference, sex
differences relatively stable
Disconfirmed
Traits typically higher in men
Openness Gender equity unrelated to open-
ness, sex differences relatively
stable
Disconfirmed
Machiavellianism Gender equity decreases Machiavel-
lianism, more so in women—sex
differences widen
Disconfirmed
Narcissism Gender equity decreases Narcissism,
more so in women—sex differences
widen
Disconfirmed
Table 11.1 Social role theory and predictions about the effects of sociopolitical gender equity on
sex differences across cultures
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11 The Evolution of Culturally-Variable Sex Differences…
increases in extraversion among both men and women, but the increase is greater
among women, leading to wider sex differences in nations with higher gender eq-
uity. This is not always the profile of sex difference variation across cultures. How-
ever, in most cases, higher levels of egalitarian sex role socialization and greater
sociopolitical gender equity are linked with larger sex differences in extraversion
across cultures, in direct contradiction to social role theory.
Trait Effects of increasing sociopolitical
gender equity on sex differences
across cultures
Social role prediction
Psychopathy Gender equity decreases psychopa-
thy, more so in women—sex differ-
ences widen
Disconfirmed
Social dominance orientation Gender equity unrelated to social
dominance, sex differences rela-
tively stable
Disconfirmed
Dismissing attachment Gender equity decreases dismissing
attachment, more so in women—sex
differences widen
Disconfirmed
Sociosexuality (SOI) overall Gender equity increases sociosexu-
ality, more so in women—sex differ-
ences narrow
Confirmed
SOI “enjoy casual sex” Gender equity increases sociosexual
“enjoy casual sex,” more so in
men—sex differences widen
Disconfirmed
Attractiveness mate preference Gender equity decreases attrac-
tiveness preference, more so in
women—sex differences widen
Disconfirmed
Self-esteem Gender equity unrelated to self-
esteem, sex differences relatively
stable
Disconfirmed
Subjective well-being Gender equity unrelated to subjec-
tive well-being, sex differences
relatively stable
Disconfirmed
Height Gender equity increases height,
more so in men—sex differences
widen
Disconfirmed
Body mass index/obesity Gender equity increases body mass
index and obesity, more so in men—
sex differences widen
Disconfirmed
Blood pressure Gender equity increases blood pres-
sure, only in men—sex differences
widen
Disconfirmed
Spatial rotation ability Gender equity increases spatial rota-
tion ability, more so in men—sex
differences widen
Disconfirmed
Occupation preference Gender equity unrelated to sys-
tematic occupation preference, sex
differences relatively stable
Disconfirmed
Table 11.1 (continued)
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14 D. P. Schmitt
Women also score higher in agreeableness and conscientiousness than men.
Increasing levels of egalitarian sex role socialization and greater sociopolitical
gender equity are generally associated with increases in agreeableness and consci-
entiousness among both men and women, but increases are greater among women,
leading to wider sex differences in nations with higher gender equity. Neuroticism
is also higher in women than men across cultures. Increasing levels of egalitarian
sex role socialization and greater sociopolitical gender equity are generally asso-
ciated with lower neuroticism among both men and women, but the decrease is
greater among men, leading to wider neuroticism sex differences in nations with
higher gender equity. Men are slightly higher in openness to experience, but this
sex difference is unrelated to gender equity. Nonetheless, because social role theory
predicts sex difference to be smaller in nations with more egalitarian sex role social-
ization and greater sociopolitical gender equity, social role theory is disconfirmed
by this finding, as well (see Table 11.1).
Dark Triad Personality Traits Several studies have found sex differences in Dark
Triad personality traits, with men typically scoring higher in Machiavellianism,
Narcissism, and psychopathy (Foster et al. 2003; Jonason et al. 2009; McHoskey
2001). Social role theory predicts that sex differences in Dark Triad personality
traits will be smaller in nations with more egalitarian sex role socialization and
greater sociopolitical gender equity. The ISDP-2 empirically evaluated these pre-
dictions of social role theory (Schmitt et al. 2014). In almost every instance, the
observed pattern of sex differences across cultures strongly disconfirmed social role
theory’s predictions (see Table 11.1).
For example, Schmitt et al. (2014) found that both men and women are lower in
Machiavellianism in nations with more egalitarian sex role socialization and greater
sociopolitical gender equity. However, the effect on women, r(46) = − 0.48, p < .05,
was much stronger than the effect on men, r(46) = − 0.19. As result, the degree of
sex difference in Machiavellianism was wider or larger in magnitude in nations
with more egalitarian sex role socialization and greater sociopolitical gender eq-
uity (e.g., the effect size of national sex differences in Machiavellianism correlated
positively with national GEM scores, r(46) = 0.57, p < .001. As an illustration, larger
sex differences in Machiavellianism were found in high egalitarian cultures such
as Netherlands ( d = 0.63), Iceland ( d = 0.61), New Zealand ( d = 0.60), and Den-
mark ( d = 0.55). Smaller sex differences in Machiavellianism were found in less
egalitarian cultures such as Ethiopia ( d = − 0.09), Malaysia ( d = − 0.10), Bangladesh
( d = − 0.17), and Swaziland ( d = − 0.19). Very similar cross-cultural results were
observed for sex differences in the Dark Triad traits of Narcissism and psychopa-
thy. As noted in Table 11.1, cross-cultural patterns of sexual differentiation in Dark
Triad traits strongly disconfirmed sex role theory.
Social Dominance Orientation Sex differences in social dominance orientation
have been documented such that men report significantly higher social domi-
nance orientation than women (Sidanius et al. 2000; Sidanius and Pratto 1999).
Generally, these sex differences have been found to be invariant across cultures.
Schmitt et al. (2014) assessed social dominance orientation across 54 nations of
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11 The Evolution of Culturally-Variable Sex Differences…
the ISDP–2 and found neither men’s nor women’s reported social dominance lev-
els were related to egalitarian sex role socialization or greater sociopolitical gen-
der equity. As noted in Table 11.1, cross-cultural patterns of sexual differentiation
in social dominance orientation strongly disconfirmed sex role theory.
Romantic Attachment Styles Sex differences in adult romantic attachment have
been documented such that men report significantly more dismissing attachment
levels than women (Bartholomew and Horowitz 1991; Del Giudice 2011). The find-
ing of sex differences in dismissing romantic attachment seems to fit with social
role theory, in that men are often socialized to be less emotional, less nurturing,
and less willing to connect with others (Bem 1993). However, Schmitt et al. (2003)
found sex differences in dismissing attachment were larger in nations with more
egalitarian sex role socialization and greater sociopolitical gender equity. As noted
in Table 11.1, cross-cultural patterns of sexual differentiation in dismissing attach-
ment strongly disconfirmed sex role theory.
Love Sex differences in love have been documented such that women report sig-
nificantly higher levels of many love styles and emotional investment tendencies
than men (Bailey et al. 1987; Hendrick and Hendrick 1995; Schmitt and Buss
2000). Schmitt et al. (2009) found both men and women report higher levels of
emotional investment in nations with more egalitarian sex role socialization and
greater sociopolitical gender equity. However, the effects on women were more
profound, leading to larger sex differences in emotional investment in nations with
more egalitarian sex role socialization and greater sociopolitical gender equity. As
noted in Table 11.1, cross-cultural patterns of sexual differentiation in emotional
investment strongly disconfirmed sex role theory.
Sociosexuality Sex differences in sociosexuality (i.e., attitudes toward having sex
without commitment) have been documented such that men report significantly
more unrestricted or permissive sociosexuality than women (Lippa 2009; Schmitt
2005b; Simpson and Gangestad 1991; see also Petersen and Hyde 2010). Schmitt
(2005b) found both men and women reported higher sociosexuality in nations with
more egalitarian sex role socialization and greater sociopolitical gender equity.
However, the effects on women were more profound, leading to more moderate sex
differences in sociosexuality in nations with more egalitarian sex role socialization
and greater sociopolitical gender equity. Lippa (2009) replicated these results in a
53-nation study, concluding “although culture moderated the magnitude of sex dif-
ferences, it was never the case that culture eliminated these sex differences, which
remained quite powerful overall, despite the presence of significant cultural main
effects and interactions” (p. 644). Even so, as noted in Table 11.1, cross-cultural pat-
terns of sexual differentiation in sociosexuality strongly confirmed sex role theory.
Sociosexual—Enjoy Casual Sex with Different Partners Sex differences in socio-
sexuality item “I can imagine myself being comfortable and enjoying ‘casual’ sex
with different partners” have been documented such that men report significantly
more enjoyment of casual sex with different partners than women (Schmitt et al.
2014). Schmitt et al. (2014) found both men and women report higher enjoyment of
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16 D. P. Schmitt
casual sex with different partners in nations with more egalitarian sex role social-
ization and greater sociopolitical gender equity. However, the effects on men were
more profound, leading to larger sex differences in enjoyment of casual sex with
different partners in nations with more egalitarian sex role socialization and greater
sociopolitical gender equity. As noted in Table 11.1, cross-cultural patterns of sex-
ual differentiation in enjoyment of casual sex with different partners strongly dis-
confirmed sex role theory.
Why the difference between the cross-cultural patterns of overall sociosexual-
ity and the cross-cultural patterns with the item “enjoy casual sex” with different
partners? According to Sexual Strategies Theory (Buss and Schmitt 1993), among
those men and women who pursue a short-term sexual strategy, it is expected that
men will seek larger numbers of partners than women (Schmitt et al. 2004). When
women engage in short-term mating, they are expected to be more selective than
men, particularly over genetic quality of short-term mates (Thornhill and Gangestad
2008). As a result, when more egalitarian sex role socialization and greater socio-
political gender equity “set free” or release men’s and women’s short-term mating
psychology, it can be expected that the specific item “enjoy casual sex with differ-
ent partners” taps the release of men’s evolved short-term mating psychology more
than women’s evolved short-term mating psychology.
Mate Preferences for Resources Sex differences in long-term mate preferences for
cues to resource provisioning ability have been documented such that women report
significantly more desire for long-term mates with status and resources than men do
(Buss and Schmitt 1993; Ellis 1992; Feingold 1992; Li et al. 2002; Sprecher et al.
1994). Eagly and Wood (1999) found both men and women report less desire for
long-term mates with resources in nations with more egalitarian sex role socialization
and greater sociopolitical gender equity. However, the effects on women were more
profound, leading to smaller sex differences in the desire for long-term mates with
resources in nations with more egalitarian sex role socialization and greater sociopo-
litical gender equity (see also Kasser and Sharma 2000; Zentner and Mitura 2012).
Specifically, Eagly and Wood (1999) found in one of four statistical tests that na-
tions with greater sociopolitical gender equity had smaller sex differences in “Good
Financial Prospects” preferences. In a recent replication, Zentner and Mitura (2012)
found sex differences in “Ambition” shrink from a moderate effect size ( d = − .65)
in lowest gender equity nations to a still moderate effect size ( d = −0.48) in high-
est gender parity nations (see Schmitt 2012). Similar results were found for sex
differences in desires for Social Status ( d = −0.31) and Good Financial Prospects
( d = −0.55). Across only the highest gender equity nations, the average sex differ-
ence ׀d׀ was 0.42 which places sex differences in long-term mate preferences for
resources in the 81st percentile of all meta-analytically documented psychological
sex differences (Hyde 2005). Thus, although these results are consistent with social
role theory, the results do not suggest sex differences in resource preferences elimi-
nated in high equity cultures. Additionally, Gangestad et al. (2006) demonstrated
the ability of social role theory to explain sex differences in resource preferences
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11 The Evolution of Culturally-Variable Sex Differences…
is negated after controlling for ecological factors. Even so, as noted in Table 11.1,
cross-cultural patterns of sexual differentiation in the desire for long-term mates
with resources at least partially confirmed sex role theory.
Mate Preferences for Attractiveness Sex differences in long-term mate preferences
for cues to beauty and youth have been documented such that men report signifi-
cantly more desire for physically attractive long-term mates than women do (Buss
and Schmitt 1993; Buss 1989; Feingold 1990; Li et al. 2002; Lippa 2007; Wheatley
et al. 2014). These sex differentiated mate preferences have been documented in
studies of real-life personal ads, online dating choices, and actual marital choice; in
studies of older adults and nationally representative samples; and in studies of the
outcomes of these preferences on patterns of jealousy, mate retention, and fertility
(for a review, see Schmitt 2014). These sex differences also have been shown to
vary in adaptive ways across cultures (Gangestad et al. 2006).
Zentner and Mitura (2012) found sex differences in preferences for physical at-
tractiveness increase from a small effect size ( d = 0.24) in lowest gender equity
nations to a moderate effect size ( d = 0.51) in highest gender parity nations (see
Schmitt 2012). Schmitt et al. (2014) also found sex differences in long-term mate
preferences for physical attractiveness are largest in nations with more egalitarian
sex role socialization and greater sociopolitical gender equity, particularly because
women, but not men, reduce their desire for physical attractiveness in long-term
mates within egalitarian sex role socialization and greater sociopolitical gender eq-
uity nations. As noted in Table 11.1, cross-cultural patterns of sexual differentia-
tion in long-term mate preferences for attractiveness strongly disconfirmed sex role
theory.
Self-Esteem Sex differences in self-esteem have been documented such that men
report significantly higher self-esteem than women (Kearney-Cooke 1998; Kling
et al. 1999). In the ISDP-2, Schmitt et al. (2014) found both men and women report
higher levels of self-esteem in nations with more egalitarian sex role socialization
and greater sociopolitical gender equity. However, the effects on men were more
profound, leading to larger sex differences in self-esteem in nations with more egal-
itarian sex role socialization and greater sociopolitical gender equity. As noted in
Table 11.1, cross-cultural patterns of sexual differentiation in self-esteem strongly
disconfirmed sex role theory.
Subjective Well-Being Sex differences in subjective well-being have been docu-
mented such that men report somewhat higher subjective well-being than women,
though this is mainly due to women’s heightened negative affect responsivity (Fujita
et al. 1991) and differences are often negligible after controlling for other demo-
graphic factors (Diener et al. 1999; Lucas and Gohm 2000). Even so, in the ISDP-2
Schmitt et al. (2014) found both men and women report higher levels of subjective
well-being in nations with more egalitarian sex role socialization and greater socio-
political gender equity. However, the effects of egalitarian sex role socialization on
men were more profound, leading to larger sex differences in subjective well-being
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18 D. P. Schmitt
in nations with more egalitarian sex role socialization. The effects of greater socio-
political gender equity on men and women were similar, leading to no association
between sociopolitical gender equity and sex differences in subjective. As noted in
Table 11.1, these cross-cultural patterns of sexual differentiation in subjective well-
being strongly disconfirmed sex role theory.
Intimate Partner Violence (IPV) Sex differences in IPV have been documented such
that women report significantly higher perpetration of IPV than men (Archer 2000;
Magdol et al. 1997). For example, Archer (2000, 2006) analyzed reports of IPV
across more than 70 nations, finding that women self-report perpetrating IPV more
than men do. Examining sex differences in the Conflict Tactics Scale (Straus 1979,
2008), Archer found more women than men perpetrated most acts of IPV. In the
ISDP-2, Schmitt et al. (2014) also examined sex differences in perpetration of IPV
using a self-report measure (Dobash et al. 1998), finding both men and women
report lower levels of IPV in nations with more egalitarian sex role socialization
and greater sociopolitical gender equity. However, the effects of egalitarian sex role
socialization on men were more profound, leading to larger sex differences in IPV
in nations with greater sociopolitical gender equity and more egalitarian sex role
socialization. As noted in Table 11.1, these cross-cultural patterns of sexual differ-
entiation in IPV strongly disconfirmed sex role theory.
Height Sex differences in height have been documented such that men are taller
than women across all cultures (Gaulin and Boster 1985; Lippa 2009), a difference
that likely has been consistent since 150,000 years ago or even earlier (Ruff 2002).
In the ISDP-2, Schmitt et al. (2014) found both men and women report taller height
in nations with more egalitarian sex role socialization and greater sociopolitical
gender equity. However, the effects on men were more profound, leading to larger
sex differences in height in nations with more egalitarian sex role socialization and
greater sociopolitical gender equity (see also, Lippa 2009). As noted in Table 11.1,
cross-cultural patterns of sexual differentiation in height strongly disconfirmed sex
role theory (cf. Touraille 2013).
Body Mass Index (BMI) and Obesity Sex differences in body mass index and obe-
sity have been documented such that men are often slightly higher on these charac-
teristics than women (Eveleth and Tanner 1990; Pasco et al. 2012). In the ISDP-2,
Schmitt et al. (2014) found both men and women report larger BMI and obesity
rates in nations with more egalitarian sex role socialization and greater sociopo-
litical gender equity. However, the effects on men were more profound, leading to
larger sex differences in BMI and obesity in nations with more egalitarian sex role
socialization and greater sociopolitical gender equity. As noted in Table 11.1, cross-
cultural patterns of sexual differentiation in BMI and obesity strongly disconfirmed
sex role theory.
Blood Pressure Sex differences in blood pressure have been documented such that
men have higher blood pressures than women (Hottenga et al. 2005). Schmitt et al.
(2014) found men report higher blood pressure in nations with more egalitarian sex
role socialization and greater sociopolitical gender equity, whereas women’s blood
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11 The Evolution of Culturally-Variable Sex Differences…
pressure is unrelated, leading to larger sex differences in blood pressure in nations
with more egalitarian sex role socialization and greater sociopolitical gender equity.
As noted in Table 11.1, cross-cultural patterns of sexual differentiation in blood
pressure disconfirmed sex role theory.
Spatial Rotation Ability Sex differences in spatial rotation ability have been docu-
mented such that men have better spatial rotation ability than women (Silverman
et al. 2007; Silverman et al. 1996; Voyer et al. 1995). In a large cross-cultural study,
Lippa et al. (2010) found both men and women report better spatial rotation abil-
ity in nations with more egalitarian sex role socialization and greater sociopolitical
gender equity. However, the effects on men were more profound, leading to larger
sex differences in spatial rotation ability in nations with more egalitarian sex role
socialization and greater sociopolitical gender equity. As noted in Table 11.1, cross-
cultural patterns of sexual differentiation in spatial rotation ability strongly discon-
firmed sex role theory.
Spatial Location Ability Sex differences in spatial location ability have been docu-
mented such that women have better spatial location ability than men (Silverman
et al. 2007; Silverman et al. 1996; Voyer et al. 2007). In a large cross-cultural study,
Silverman et al. (2007) found men’s and women’s spatial location abilities were
unrelated to egalitarian sex role socialization and sociopolitical gender equity. As
noted in Table 11.1, cross-cultural patterns of sexual differentiation in spatial loca-
tion ability disconfirmed sex role theory.
Crying Sex differences in crying behavior have been documented such that women
cry more than men (Becht et al. 2001; Lombardo et al. 2001; Santiago-Menendez
and Campbell 2013; van Hemert et al. 2011; Vingerhoets and Scheirs 2000). Evalu-
ating national data from van Hemert et al. (2011), Schmitt et al. (2014) found both
men and women report crying more in nations with more egalitarian sex role social-
ization and greater sociopolitical gender equity. However, the effects on women
were more profound, leading to larger sex differences in crying behavior in nations
with more egalitarian sex role socialization and greater sociopolitical gender equity.
As noted in Table 11.1, cross-cultural patterns of sexual differentiation in crying
behavior strongly disconfirmed sex role theory.
Depression Sex differences in depression have been documented such that
women have nearly twice the rate of depression as men (Fischer and Manstead
2000; Hopcroft and McLaughlin 2009; Nolen-Hoeksema 2001). Hopcroft and
McLaughlin (2009) found both men and women report lower rates of depression
in nations with more egalitarian sex role socialization and greater sociopolitical
gender equity. However, the effects on men were more profound, leading to larger
sex differences in depression in nations with more egalitarian sex role socialization
and greater sociopolitical gender equity. As noted in Table 11.1, cross-cultural pat-
terns of sexual differentiation in depression strongly disconfirmed sex role theory.
Values Sex differences in values have been documented such that women report
higher levels of benevolence and universalism values, whereas men report higher
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levels of power, achievement, and hedonism values (Schwartz and Rubel 2005;
Schwartz and Rubel-Lifshitz 2009). Schwartz and Rubel (2005) and Schwartz and
Rubel-Lifshitz (2009) found both men and women report higher benevolence in
nations with more egalitarian sex role socialization and greater sociopolitical gen-
der equity. However, the effects on women were more profound, leading to larger
sex differences in benevolence in nations with more egalitarian sex role socializa-
tion and greater sociopolitical gender equity. Similar findings were observed for
sex differences in universalism, power, achievement, and hedonism. As noted in
Table 11.1, cross-cultural patterns of sexual differentiation in values strongly dis-
confirmed sex role theory.
Occupational Preferences and Interests Sex differences in occupational prefer-
ences and interests have been documented such that men report significantly more
interest in systematic, thing-oriented professions and women report significantly
more interest in empathetic, people-oriented professions (Konrad et al. 2000; see
also Nettle 2007; Su et al. 2009). Lippa (2010) found across 53 nations that men’s
and women’s occupational preferences are entirely unrelated to egalitarian sex role
socialization and greater sociopolitical gender equity. As noted in Table 11.1, cross-
cultural patterns of sexual differentiation in occupational preferences disconfirmed
sex role theory.
Nation-Level Covariates as Alternative Explanations The highly consistent pattern
of sex differences getting larger in nations with more egalitarian sex role social-
ization and greater sociopolitical gender equity could be explained by forces that
statistically overwhelm the power of social role theory to explain sex differences.
For instance, sex role socialization and sociopolitical gender equity are highly cor-
related with wealth, prevalence of education, and overall human development of
nations. Schmitt et al. (2014) noted that after controlling for these and other fac-
tors, virtually all of the above findings that disconfirmed social role theory still
emerge. Indeed, many of the counter-intuitive associations between sex differences
and sociopolitical gender equity increased after controlling for potential covariates.
For instance, the finding that sex differences in neuroticism were larger in nations
with more progressive sex role ideology was intensified after controlling for gross
domestic product of nation. The same was true for links between sex differences
in neuroticism and the gender gap index, the gender equality index, and the SIGE.
Future research should examine multiple control variables in ways that allow for a
more complete evaluation of these alternative explanations (see Nettle 2009).
Reference-Group Effects as Alternative Explanations Guimond et al. (2007, 2008)
have suggested that sex differences in self-reported personality traits are suppressed in
less progressive nations because of reference-group effects. That is, men and women
may compare themselves only to their own gender when completing surveys in less
progressive cultures, but in more progressive nations men and women compare them-
selves to everyone, resulting in more accurate sex differences in nations with egali-
tarian sex role socialization and greater sociopolitical gender equity (Biernat et al.
1991). If true, this has dire implications for gender similarities theory (Hyde 2005).
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11 The Evolution of Culturally-Variable Sex Differences…
It would suggest that the moderate to large sex differences commonly observed in
more progressive Northern European nations are “truer” estimates of psychologi-
cal sex differences (after all, men and women are comparing themselves to every-
one, not just their own gender), whereas in more traditional cultures researchers are
merely observing masked versions of what, according to social role theory, must be
incredibly larger sex differences in personality (Lukaszewski et al. 2013). Finding
that so many sex differences in psychology range from large in egalitarian nations
to extremely large in more traditional cultures would provide strong refutation of
gender similarities theory (Hyde 2005). According to Fischer (2010), Lippa (2009),
and Schmitt et al. (2014), such a perspective is unlikely for several reasons.
First, if reference-group effects were masking sex differences in traditional cul-
tures, researchers should observe smaller standard deviations in men’s and women’s
distributions in traditional cultures compared to more progressive cultures (where
men and women compare themselves to everyone). Empirically, this is typically not
the case (Fischer 2010; Lippa 2009; Schmitt et al. 2014). Second, if reference-group
effects were the driving force behind counter-intuitively larger sex differences in
egalitarian nations, researchers should observe all survey items are equally effected
by reference-group effects. Again, this is not the case empirically (Fischer 2010;
Lippa 2009; Schmitt et al. 2014). Third, if reference-group effects were the driv-
ing force behind counter-intuitively larger sex differences in egalitarian nations,
researchers should observe both men and women are equally biased in their re-
sponses. Again, this is not the case (Fischer 2010; Lippa 2009; Schmitt et al. 2014).
An additional limitation of reference-group effects for discounting the robust
disconfirmation of social role theory in this review is that many of the findings re-
viewed earlier transcend of the reference-group limitations of self-report methods.
Reference-group effects cannot explain the finding that sex differences in height,
BMI, obesity, and blood pressure are larger in cultures with more egalitarian sex
role socialization and greater sociopolitical gender equity. Reference-group effects
cannot explain the finding that sex differences in tested spatial rotation and spatial
location abilities are larger in cultures with more egalitarian sex role socialization
and greater sociopolitical gender equity. Such measures represent fair “common
rule” tests of social role theory (Biernat et al. 1991), and in nearly every case social
role theory was strongly disconfirmed.
Additional Psychological Traits to Consider Not all psychological sex differences
have been measured across large numbers of nations in a way that allows research-
ers to relate the size of nation-level sex differences to indicators of sex role social-
ization and sociopolitical gender equity. It is possible that additional psychological
traits will be discovered, measured, and documented as sexually differentiated
across cultures that either support or further refute social role theory. Given the
reviewed findings here, researchers should probably expect the vast majority of
future research findings that will refute social role theory.
In addition, there are some psychological traits that do not typically show sex
differences, on average, but still relate to sex role socialization and sociopolitical
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22 D. P. Schmitt
gender equity in interesting ways. For instance, although sex differences in the
high-end distribution of math scores can be substantial (Halpern et al. 2007), mean-
level sex differences in math ability have been shown to be minimal (Hyde et al.
1990; Hyde and Mertz 2009). In one of two cross-cultural datasets, Else-Quest et al.
(2010) found no significant links between the size of a nation’s mean-level sex
difference in math and indicators of global sociopolitical gender equity. However,
in another dataset they did find some links. Importantly, the size of a nation’s sex
difference in math was most closely associated with national indicators of women
being given greater access to education and research jobs, with such indicators
having positive associations with women’s (more so than men’s) math scores. The
precision with which Else-Quest et al. (2010) identified this potential sociological
source of psychological sex difference is laudable and informative, but their overall
findings did not provide broad sweeping confirmation of social role theory.
Evaluating Life History Theory as a Facultative Mediator
of Sex Differences Across Cultures
According to evolutionary psychologists who take life history approaches (Ellis
et al. 2009; Geary 2002; Kaplan and Gangestad 2005), many human psychological
adaptations are facultatively designed to attend to particular sources of ecological
information and generate specially-designed, highly functional forms of behavior.
As a result, many aspects of human culture—including the magnitude or degree of
sex differences across human cultures—can be both evolved and variable. In par-
ticular, ecological stress is thought to have a profound effect on men’s and women’s
psychology, and does so in a slightly different way in men and women.
According to Psychosocial Acceleration Theory (Belsky 2012; Belsky et al.
1991), in stressful ecological contexts, both men and women are thought to fac-
ultatively pursue a faster life history strategy composed of psychological traits in-
cluding dismissing attachment, anti-sociality, short-term temporal orientations, and
prolific short-term mating. Many of these traits display a sex difference such that
men are higher in the trait than women. Because the effects of ecological stress are
thought to be more profound among women on many of these traits (Ellis 2004),
researchers often expect smaller sex differences in high stress cultures (Schmitt
2011). As shown in Table 11.2, based on measures of national pathogen stress
(Fincher and Thornhill 2012) and responses to personality scales across multiple
studies, eight psychological traits relevant to Psychosocial Acceleration Theory
followed the predicted pattern of sexual differentiation across cultures, including
sex differences in love, resource mate preferences, Narcissism, psychopathy, social
dominance orientation, dismissing attachment, attractiveness mate preferences, and
self-esteem. Four traits disconfirmed this theory, including sex differences in agree-
ableness, Machiavellianism, sociosexuality, and sociosexual enjoy casual sex (see
also, Schmitt 2005b).
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11 The Evolution of Culturally-Variable Sex Differences…
Evaluating Religiosity as an Emergent Moderator
of Sex Differences Across Cultures
As noted earlier, religion may be an especially potent “emergent moderator” of psy-
chological adaptations in men and women across cultures (e.g., Kirkpatrick 2011;
McCullough et al. 2012; Mealey 1985). Some researchers expect most religions will
suppress psychological adaptations involving short-term mating, and do so more
Table 11.2 Life history theory and predictions about the effects of local ecology on sex differ-
ences across cultures
Trait Effects of ecological stress on sex
differences across cultures
Life history prediction
Traits typically higher in women
Agreeableness Ecological stress increases agree-
ableness in men and women—sex
differences stable
Disconfirmed
Love Ecological stress decreases love,
more so in women—sex differences
narrow
Confirmed
Resources mate preference Ecological stress increases resources
preferences, more so in women—
sex differences widen
Confirmed
Traits typically higher in men
Machiavellianism Ecological stress decreases Machia-
vellianism, more so in men—sex
differences narrow
Disconfirmed
Narcissism Ecological stress increases Narcis-
sism, more so in women—sex
differences narrow
Confirmed
Psychopathy Ecological stress increases psy-
chopathy, only in women—sex
differences narrow
Confirmed
Social dominance orientation Ecological stress increases social
dominance orientation, only in
women—sex differences narrow
Confirmed
Dismissing attachment Ecological stress increases dismiss-
ing attachment, more so in women—
sex differences narrow
Confirmed
Sociosexuality (SOI) overall Ecological stress decreases socio-
sexuality, more so in women—sex
differences widen
Disconfirmed
SOI “enjoy casual sex” Ecological stress decreases “enjoy
casual sex” in men and women—sex
differences stable
Disconfirmed
Attractiveness mate preference Ecological stress increases attrac-
tiveness preferences, more in
women—sex differences narrow
Confirmed
Self-esteem Ecological stress increases self-
esteem, only in women—sex
differences narrow
Confirmed
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24 D. P. Schmitt
to women’s than men’s short-term mating psychology (Baumeister and Twenge
2002). In addition, religion might enhance psychological adaptations having to do
with prosociality and reduce antisociality (Fincher and Thornhill 2012; Weeden and
Kurzban 2013), and do so more in one sex than the other. As shown in Table 11.3,
based on measures of religiosity and personality in the ISDP-2, seven psychological
traits followed this pattern, including sex differences in agreeableness, love, Machi-
avellianism, Narcissism, psychopathy, social dominance orientation, and dismiss-
ing attachment. Two traits disconfirmed these predictions, including sex differences
in sociosexuality and sociosexual enjoy casual sex.
Conclusion
Only a few decades ago, parental socialization of children was thought to be a pri-
mary force in the constructivist shaping of children’s psychological traits (Bruner
1986; Fosnot 1996). Today, psychologists know from genetically-informative
Table 11.3 Religion’s emergently-moderated sex differences across cultures
Trait Effects of religiosity on sex differ-
ences across cultures
Suppression prediction
Traits typically higher in women
Agreeableness Religiosity increases agreeableness,
more so in men—sex differences
narrow
Confirmed
Love Religiosity decreases love, more so
in women—sex differences narrow
Confirmed
Traits typically higher in men
Machiavellianism Religiosity decreases Machiavel-
lianism, only in men—sex differ-
ences narrow
Confirmed
Narcissism Religiosity decreases Narcissism,
only in men—sex differences
narrow
Confirmed
Psychopathy Religiosity decreases psychopa-
thy, only in men—sex differences
narrow
Confirmed
Social dominance orientation Religiosity decreases social domi-
nance orientation, more so in men—
sex differences narrow
Confirmed
Dismissing attachment Religiosity increases dismissing
attachment, more so in women—
sex differences narrow
Confirmed
Sociosexuality (SOI) overall Religiosity decreases sociosexuality,
more so in women—sex differences
widen
Disconfirmed
SOI “enjoy casual sex” Religiosity decreases “enjoy casual
sex” in men and women—sex
differences relatively stable
Disconfirmed
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11 The Evolution of Culturally-Variable Sex Differences…
designs that children’s genes often evoke parental behaviors that only appear to
be socializing factors (Kagan 1999), and shared genes among biological parents
and their children account for much of the ostensible association between paren-
tal behavior and childhood personality (Krueger and Johnson 2008; Plomin 2008).
Psychologists no longer place most of the blame for children’s personality traits and
mental health outcomes on parental socialization (Harris 1998; Maccoby 2000). In
a similar manner, new knowledge from cross-cultural research suggests that sex
role socialization may no longer be to blame for most patterns of psychological sex
differences across cultures (see also, Udry 2000). Instead, evolved combinations
of men’s and women’s obligate, facultatively-mediated, and emergently-moderated
psychological adaptations may better account for sex differences across cultures.
In this chapter, evidence was marshaled across 21 data sources that evaluated
the foundational assumption of social role theory that psychological sex differences
directly result from sex role socialization and that, as consequences, psychological
sex differences will be smaller in cultures with more egalitarian sex role socializa-
tion and greater sociopolitical gender equity. Empirically, sex differences in most
psychological traits—in personality, sexuality, attitudes, and cognitive abilities—
are conspicuously larger in cultures with more egalitarian sex role socialization and
greater sociopolitical gender equity. Even sex differences in many physical traits
such as height, obesity, and blood pressure were shown to be larger in cultures
with more egalitarian sex role socialization and greater sociopolitical gender equity.
Three alternative evolutionary perspectives on sex differences—obligate, faculta-
tive-mediation, and emergent-moderation—appeared to better explain the universal
and culturally-variable sex differences reliably observed across cultures.
From an evolutionary perspective, it would be remarkable if men and women
have not evolved at least some differences in psychological design. Indeed, as Van-
dermassen (2011) has noted, “that human males and females should have evolved
to be psychologically identical, for example, is a theoretical impossibility, and, in-
deed, turns out to be untrue” (p. 733). At this point, it is perhaps unscientific to
assert absolutely no sex-specific psychological adaptations exist in humans (Buss
and Schmitt 2011; Kenrick et al. 2010), yet many social scientists continue to assert
this is so (Winegard et al. 2014). One reason behind the extreme popularity of the
SSSM’s sex difference denialism is that magnitude of many sex differences notice-
ably varies across cultures. Because this variation is in a few cases linked to sex
role variation in ways consistent with social role theory across cultures (e.g., mate
preferences for resources), some researchers have spotlighted these few peculiar
cases and advanced all-encompassing theories about the primary causal force of sex
roles in generating psychological sex differences across cultures (Eagly and Wood
1998; Wood and Eagly 2002). In this chapter, the legitimacy of social role explana-
tions as the sole source of psychological sex differences has been called into seri-
ous question (see also Udry 2000). In most cases, the cross-cultural evidence has
directly refuted patriarchal social role explanations of sex differences. Social role
theory, as a theory that purportedly explains the degree of psychological sex differ-
ences across cultures, should probably be considered a scientific dead end. At the
very least, psychological science needs other perspectives to explain the sweeping
patterns of culturally variable sex differences documented in this chapter.
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Evolutionary perspectives take a different and ultimately more profitable ap-
proach to understanding the relationship between culture and sex differences in psy-
chology (Campbell 2002). First, evolutionary psychology perspectives offer mech-
anisms for why cultural universals and cultural variations exist in sex differences
(see Pirlott and Schmitt 2014). For example, Gangestad et al. (2006) explained that
universal sex differences in mate preferences for physical attractiveness are univer-
sally generated by evolved sex-specific psychological adaptations, but these mecha-
nisms are also facultatively mediated by local ecology—if environments have high
pathogen prevalence, then mate preferences for physical attractiveness are adap-
tively enhanced. If the local environment has low pathogen prevalence, then adap-
tive desires de-emphasize physical attractiveness in potential mates.
Second, evolutionary psychology perspectives offer explanations of cultural
change (Mesoudi et al. 2006). When levels of pathogen prevalence shift within a
culture, the corresponding emphasis on physical attractiveness should shift in that
culture, as well. Moreover, the degree to which pathogens affect the adaptations one
sex more than the other would explain why the size of sex differences varies across
cultures. Thus, evolutionary perspectives on phenotypic plasticity and evoked cul-
ture such as Gangestad et al. (2006) possesses the ability to explain pancultural
universals and facultative variations, something very much missing from SSSM
accounts of culture and sexuality (Maccoby 2000). It is not the case that all aspects
of culture will be subject to evolutionary explanations, at least in terms of genetic
evolution (see Brown et al. 2011). Still, by combining genetic and cultural levels of
evolution in sophisticated ways—utilizing obligate, facultatively-mediated, emer-
gently-moderated, and social role approaches—more complete and scientifically
fruitful understandings of psychological sex differences will prosper.
References
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