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Ideological Bias in the Psychology of Sex and Gender

November 2020

In book: Political bias in psychology: Nature, scope, and solutions
Publisher: Springer

Authors:

Marco Del Giudice

University of New Mexico

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Ideological Bias in the Psychology of Sex and Gender

Marco Del Giudice

University of New Mexico

In press (2021):

Chapter in C. L. Frisby, W. T. O’Donohue, R. E. Redding, & S. O. Lilienfeld (Eds.)

Political bias in psychology: Nature, scope, and solutions. Springer.

[Preprint date: November 29, 2020]

Marco Del Giudice, Department of Psychology, University of New Mexico. Logan Hall, 2001

Redondo Dr. NE, Albuquerque, NM 87131, USA; email: marcodg@unm.edu

In this chapter I discuss the influence of ideological bias in the psychological study of sex

and gender. This kaleidoscopic issue would demand an entire book; attempting to be systematic

and exhaustive would be an impossible task. Instead, I take a somewhat informal approach as I

try to highlight key points of tension, clarify some conceptual muddles, offer interesting

examples, and put everything in historical perspective. The last bit is especially important,

because the received history of this topic is also ideologically slanted and full of distortions, half-

truths, and sometimes sheer fabrications. To delimit the field and remain close to the topic of this

volume, I focus mainly on academic psychology, leaving aside the applied psychological

disciplines (e.g., psychotherapy) and the neurosciences.

The Problem in a Nutshell

As pointed out by Winegard and Winegard (2018), bias in the social sciences is more

often ideological than narrowly political (in the sense of left- vs. right-wing partisanship); the

reason why sex and gender are hot topics is that they play a central role in egalitarian ideologies,

of which feminism is a prime example. Most present-day feminists embrace what Winegard and

Winegard labeled cosmic egalitarianism, or the belief that all ethnic and cultural groups, social

classes, and sexes are relatively equal on all socially desired traits; note that “equal” should be

read as biologically equal, because measurable differences may also arise because of differential

socialization, prejudice, and discrimination.

Thus, egalitarianism and desire for social change

toward equality go hand in hand with a social constructionist, “blank slate” perspective on

human nature (see e.g., Anomaly & Winegard, 2019; Eagly, 2018; Pinker, 2003; Murray, 2020;

Winegard & Winegard, 2018). In short:

Feminist theorists view gender not as a biologically created reality, but as a

socially constructed phenomenon (Else-Quest & Hyde, 2018, p. 13).

Many feminists are wary of biological explanations of anything, in large part

because biology always seems to end up being a convenient justification for

perpetuating the status quo (ibid., p. 45).

Because feminism is the dominant ideological influence in the study of sex and gender,

this chapter takes a critical stance toward feminist theory and research. However, my goal is not

to write an anti-feminist pamphlet. There is no doubt that feminist scholars have made valuable

contributions to psychology and brought attention to important themes; evolutionary

psychologists like myself have long recognized this (e.g., Buss & Schmitt, 2011; Campbell,

2006; Nicolas & Welling, 2015). In a recent exchange we had with some prominent feminist

scientists, my colleagues and I found several points of agreement despite our different

perspectives (Del Giudice et al., 2018a; Fine et al., 2018). While some feminist literature is—by

design—polemical and one-sided, this is not necessarily a problem; sometimes, ideological

So-called “Difference feminism” has been out of fashion since the late 1990s, and did not necessarily accept

biological explanations of sex differences. Of course, one can be an equal-opportunity feminist while believing that

some sex differences in behavior and cognition have a strong biological basis, and contribute to determine enduring

differences in social outcomes. But this viewpoint has virtually no traction on present-day feminism, which—

especially in academia—is moving toward increasingly extreme versions of social constructionism (see e.g., Else-

Quest & Hyde, 2018; Pluckrose & Lindsay, 2020).

biases help scholars see facts and explanations that others would miss. The dialectic can remain

healthy as long as multiple viewpoints are allowed and ideas are evaluated on their own merits.

The trouble begins when an entire field or discipline aligns in the same ideological direction, so

that certain domains of research become “sacralized” and hence systematically distorted (see

Winegard & Winegard, 2018).

From this standpoint, the state of psychological research on sex and gender is mixed, with

a lot of variation across subdisciplines (and evolutionary psychology as the biggest outlier; see

Buss, 2015; Pinker, 2003; Stewart-Williams, 2018). While sex is not nearly as sacralized as race,

certain questions border on taboo; for example, biological explanations of sex differences in

educational and occupational outcomes are likely to attract denunciations and attacks, especially

if they reach the general public. As the ideological landscape evolves, previously uncontroversial

issues become morally charged in the eyes of activists; right now, the idea that there are two

biological sexes seems on its way to become “problematic” (more on this below).

Because ideological pressures in this area of psychology are uneven and relatively subtle

(especially compared with more politicized social sciences like sociology and cultural

anthropology), they are mostly expressed as implicit “preferences” that affect the design,

interpretation, publication, and divulgation of research. Roughly speaking:

a. No differences are better than any differences (unless they are presented as evidence

of discrimination);

b. Small differences are better than large differences (same as above);

c. Variable, malleable differences are better than stable, unchanging differences;

d. Socialization is better than biology.

And the list may be expanding to include:

e. Nonbinary is better than binary.

To complete this summary, one should note that, from an egalitarian perspective,

differences are better tolerated if they reflect positively on a group that is perceived as

underprivileged or oppressed (e.g., findings of higher verbal ability in females tend to be less

controversial than findings of higher spatial and mathematical ability in males). Note that the

preferences listed above are not “wrong” in the sense that they should be reversed; to be sure,

discrimination does occur, sex differences are often small, and many traits—including evolved

traits—are expressed in a context-sensitive manner and can be shaped by the environment. The

problem is that their collective weight pushes the field in a particular direction, making it easier

(or harder) to publish certain kinds of results and formulate certain interpretations. These

preferences are enforced more rigidly when approaching controversial topics, such as sex

differences in educational and occupational outcomes. They also become more visible as one

moves from the technical literature to the public interface of the discipline—for example in

introductory textbooks, course materials, and statements by professional associations. (One

reason may be that ideological pressures in certain sections of the public are stronger than within

psychology itself.

)

The result is that important topics are presented in a slanted fashion, or not discussed at

all; they include the theory of sexual selection (see Geary, 2021); the existence of large sex

differences in occupational interests (e.g., Lippa, 2010; Morris, 2016), in multivariate profiles of

personality (e.g., Del Giudice et al., 2012; Kaiser, 2019; Kaiser et al., 2020), and at the tails of

cognitive abilities (e.g., Baye & Monseur, 2016; Wai et al., 2010, 2018); findings of temporal

and cross-cultural stability (e.g., Schmitt et al., 2003; Stoet & Geary, 2020); “paradoxical”

patterns that run against simple socialization accounts, with larger sex differences in more

gender-egalitarian countries (e.g., Falk & Hermle, 2018; Kaiser, 2019; MacGiolla & Kajonius,

2019; Schmitt et al., 2017; Stoet & Geary, 2015, 2018); and cross-species similarities in sexually

differentiated behaviors (e.g., Alexander & Hines, 2002; Benenson, 2019; Cashdan & Gaulin,

2016; Hassett et al., 2008). For recent overviews of these and related topics, see Archer (2019),

Geary (2021), and Murray (2020).

Interlude: Sex, Gender, and the Binary

Up to this point I have used “sex” and “gender” casually, but before moving ahead, it is

important to do some conceptual clean-up.

While many scholars treat these terms as more or

less synonyms (Haig, 2004), they have different histories and implications. The usage of

“gender” as the social and/or psychological counterpart of biological sex was introduced in

psychology by Money (1955), though Bentley (1945) had made the same distinction years

before. The term was popularized by Stoller (1968) and quickly adopted by feminist scholars in

the 1970s (Haig, 2004; Janssen, 2018). “Gender” was going to denote the social roles, behaviors,

and aspects of identity associated with being male or female, as distinct from the biological

characteristics of the wo sexes. The assumption was that psychological differences are largely or

exclusively determined by socialization (see Deaux, 1985; Oakley, 1972; Unger, 1979). Scholars

began to use “gender” instead of “sex” even if the proposed definitions were frustratingly

unclear. For example, a widely cited paper by Unger (1979) defined gender as:

[T]hose nonphysiological components of sex that are culturally regarded as

appropriate to males or to females. Gender may be used for those traits for

which sex acts as a stimulus variable, independently of whether those traits

have their origin within the subject or not. It refers to a social label by which

we distinguish two groups of people (Unger, 1979, p. 1086).

This definition mixes correlations with social evaluations, and individual traits with

group labels. In fact, it may be impossible to make the concept of gender fully coherent unless

one embraces a social constructionist view. The problem is that psychological traits arise from

the interplay between social and biological processes—even worse, the very distinction between

“social” and “biological” is blurry and ill-defined (see e.g., Lippa, 2005). This makes the

For a revealing example, consider the reactions to James Damore’s now-infamous “memo” on sex differences in

tech jobs (Damore, 2017; see Anomaly & Winegard, 2019).

Parts of this section are adapted from Del Giudice (2020).

distinction between sex and gender effectively unworkable, as many have noted over the years

(e.g., Blakemore et al., 2009; Eagly & Wood, 2013; Ellis et al., 2008; Haig, 2004). For a recent

illustration, consider the guidelines in the latest APA publication manual:

Gender refers to the attitudes, feelings, and behaviors that a given culture

associates with a person's biological sex […] Gender is a social construct and a

social identity. […] Sex refers to biological sex assignment; use the term “sex”

when the biological distinction of sex assignment (e.g., sex assigned at birth) is

predominant. […] In some cases, there may not be a clear distinction between

biological and acculturative factors, so a discussion of both sex and gender

would be appropriate (American Psychological Association, 2019, p. 138).

As usual, “gender” is defined from a social constructionist standpoint; but in practice, the

distinction between biology and socialization is almost never clear-cut, so authors are instructed

to discuss “both sex and gender” and then left to their own devices. Interestingly, biological sex

is defined as something that gets “assigned” to people, an expression that is largely meaningless

(unless one is talking about the treatment of intersex conditions) but conforms to the precepts of

transgender activism.

The flaws of the sex-gender distinction have led some feminist scholars to adopt the

hybrid term “sex/gender” (sometimes “gender/sex”) as a way to recognize that biological and

social factors are inseparable, and underscore the potential for plasticity (Fausto-Sterling, 2012;

Hyde et al., 2019; Jordan-Young & Rumiati, 2012; Rippon et al., 2014). Unfortunately, this

terminological fusion may end up deepening the conceptual confusion. The proponents of

sex/gender usually describe it as a continuum, or even a multidimensional collection of semi-

independent features; a person’s sex/gender can be hybrid, fluid, or otherwise nonbinary (see

e.g., Hyde et al., 2019; Morgenroth & Ryan, 2020). One crucial implication is that biological sex

is also non-binary and socially constructed, in line with the tenets of fourth-wave feminism

(Else-Quest & Hyde, 2018; Pluckrose & Lindsay, 2020). On this view, the “sex binary” is a

socially constructed fiction; the old idea that there are two sexes is simplistic and inaccurate, and

does not stand up to sophisticated analysis. Hence, “male” and “female” should be replaced with

multiple overlapping categories, or even (multi)dimensional scores of gendered self-concepts

and attitudes (Hyde et al., 2019; Joel & Fausto-Sterling, 2016). This argument can be seductive

but has one problem—it fundamentally misunderstands the nature of sex. I now briefly discuss

why.

The Real Sex Binary

In the social sciences, many scholars define sex as a collection of traits—X/Y

chromosomes, gonads, hormones, and genitals—that cluster together in most people but may

also occur in rare atypical combinations (e.g., Blakemore et al., 2009; Fausto-Sterling, 2012;

Helgeson, 2016; Joel, 2012). This definition is the basis for the widely repeated claim that up to

2% of live births are intersex (Blackless et al., 2000; see e.g., Hyde et al., 2019). In fact, the 2%

figure is a gross overestimate. Blackless et al. (2000) defined intersex very broadly as individuals

who deviate from the “Platonic ideal” of sex dimorphism; accordingly, they included several

conditions (e.g., Klinefelter syndrome, vaginal agenesis, congenital adrenal hyperplasia) that

affect sexual development but can be classified as “intersex” only in a very loose sense (Sax,

2002). If one restricts the term to conditions that involve a discordance between chromosomal

and phenotypic sex, or a phenotype that cannot be classified unambiguously as either male or

female, the frequency of intersex is almost certainly less than 0.02% (Sax, 2002; see also Hull,

2003).

On a deeper level, the “patchwork” definition of sex used in the social sciences is purely

descriptive and lacks a functional rationale. This contrasts sharply with how the sexes are

defined in biology. From a biological standpoint, what distinguishes the males and females of a

species is the size of their gametes: males produce small gametes (e.g., sperm), females produce

large gametes (e.g., eggs; Kodric-Brown & Brown, 1987).

Dimorphism in gamete size or

anisogamy is the dominant pattern in multicellular organisms, including animals. The evolution

of two gamete types with different sizes and roles in fertilization is the predictable consequence

of selection to maximize the efficiency of fertilization (Lehtonen & Kokko, 2011; Lehtonen &

Parker, 2014). In turn, anisogamy set the stage for sexual selection (i.e., selection via mating

competition and mate choice), with predictable consequences for the evolution of sexually

differentiated traits in morphology, development, and behavior (Janicke et al., 2016; Lehtonen et

al., 2016; Schärer et al., 2012). Of course, the existence of two distinct sexes does not mean that

sex-related traits must also have binary, sharply bimodal distributions. The sex binary is

perfectly compatible with large amounts of within-sex variation in anatomy, physiology, and

behavior. In fact, sexual selection often amplifies individual variability in sex-related traits

(typically more strongly in males), and can favor the evolution of multiple alternative phenotypes

within each sex (see Del Giudice et al., 2018b; Taborsky & Brockmann, 2010).

To be clear, the biological definition of sex is not just one option among many equally

valid alternatives; the very existence of differentiated males and females in a species depends on

the existence of two gamete types. Chromosomes and hormones participate in the mechanics of

sex determination and sexual differentiation, but do not play the same foundational role. The sex

binary, then, is not a fiction but a basic biological fact: even if a given individual may fail to

produce viable gametes, there are only two gamete types with no meaningful intermediate forms

(Lehtonen & Parker, 2014; see also Cretella et al., 2019). This dichotomy is not statistical but

functional, and hence is not challenged by the existence of intersex conditions (regardless of

their frequency), nonbinary gender identities, and other seeming exceptions. As a rule, scholars

who argue against the “sex/gender binary” are happy to dive into the fine details of sexual

differentiation, but typically avoid mentioning anisogamy, let alone grappling with its

implications for the evolution of the sexes. This has not stopped the misconception that “sex is

not binary” from spreading, not just in the social sciences but in the broader literature. In 2015,

Nature published a feature claiming that sex had been “redefined” along nonbinary lines

(Ainsworth, 2015); in 2020, a research update on the COVID-19 virus came with the disclaimer

“Nature recognizes that sex and gender are neither binary nor fixed” (Nature, 2020).

In the rest of the chapter, I always use “sex” and “sex differences” whenever the

distinction is between males and females as groups. When discussing research on stereotypes,

Species with simultaneous hermaphroditism (mostly plants and invertebrates) do not have distinct sexes, since any

individual can produce both types of gametes at the same time.

social perception, identity, etc., I use “sex” and “gender” in a context-sensitive manner, without

any implications about biology vs. socialization. (For example, it has become customary to talk

of “gender stereotypes” instead of “sex stereotypes”, and I use the standard label for simplicity.)

A Peek at the Recent Literature

Introductory Textbooks

For many college students, introductory textbooks represent the first or only exposure to

the field of psychology. As an informal survey of the field, I went through seven recent

introductory psychology textbooks, five traditional (Burton et al., 2019; Grison & Gazzaniga,

2019; Kalat, 2016; Morris & Maisto, 2018; Schachter et al., 2020) and two open-access (Noba

Project, 2020; Spielman, 2020). Note that I selected these textbooks based on availability, so this

should not be mistaken for a systematic overview. In two texts out of seven (Grison &

Gazzaniga; Spielman), sex differences in personality and cognition were not discussed at all,

except for some vague references to gender stereotypes. Sex differences in personality were

mentioned in only two textbooks (Kalat; Schacter et al.); in both cases, the authors described

them as small and emphasized overall similarities. All seven texts mentioned sex differences in

aggression and/or mating and noted possible biological explanations (Burton et al.; Kalat; Noba

Project; Schacter et al.), although in most cases the coverage was extremely cursory and partial.

Five textbooks addressed sex differences in cognitive abilities, while emphasizing similarity

and/or malleability (Burton et al.; Kalat; Morris & Maisto; Noba Project; Schacter et al.). One of

them cited evidence that cognitive sex differences are stable across time and places (Burton et

al.), but none discussed findings of stronger differences in gender-egalitarian countries. Five

texts introduced at least some concepts related to sexual selection, however briefly (Burton et al.;

Kalat; Morris & Maisto; Noba Project;

Schacter et al.). Finally, two texts out of seven offered

“nonbinary” accounts of sex and/or gender (Grison & Gazzaniga; Noba Project).

This quick survey illustrates many of the trends I discussed earlier. As expected, there is

an overall tendency to ignore and/or downplay sex differences, to the point that a substantial

fraction of the textbooks was partly or completely silent on the issue. At the same time, there is

quite a bit of variation in coverage, and a few outliers that deviate from the general trend. The

textbooks also revealed a tension between the standard preferences of the discipline and the

growing influence of evolutionary psychology, particularly in specific domains such as mating

and aggression (see also Ferguson et al., 2016).

Generalist Journals

Within the technical literature, generalist journals facilitate the exchange of ideas and

findings across specialized subfields. Because they publish papers from multiple areas of

research, generalist journals should provide something like an “average” picture of the discipline,

smoothing out the biases and intellectual traditions of individual areas. For this survey, I

The Noba Project textbook is a collection of stand-alone chapters, each written by different authors. Sexual

selection was discussed in the chapter on evolutionary psychology (Buss, 2020), but not in the one on gender, which

took a decidedly social-constructionist approach (Brown et al., 2020).

reviewed the papers published during the years 2018-2020 in six high-impact journals: American

Psychologist, Psychological Review, Psychological Bulletin, Annual Review of Psychology,

Current Directions in Psychological Science, and Perspectives on Psychological Science.

selected relevant papers based on their title and abstract, and counted a total of 19 articles

dealing with sex and gender.

Of the 19 papers, four centered on the idea of challenging the sex/gender binary: a widely

disseminated paper by Hyde et al. (2019); two comments to Hyde et al., one favorable (Reilly,

2019) ad one critical (Cretella et al., 2020); and a radical social-constructionist piece by

Morgenroth and Ryan (2020).

Three papers dealt specifically with gender stereotypes. These were a review of the topic

by Ellemers (2018), a historical analysis of stereotype changes in the USA by Eagly et al. (2020),

and an experimental study on negative stereotypes about the intellectual ability of girls and

women (Bian et al., 2018). In her review, Ellemers rejected the idea that gender stereotypes may

reflect actual psychological differences between the sexes (“If there is a kernel of truth

underlying gender stereotypes, it is a tiny kernel”; p. 278), and gave short shrift to possible

biological explanations. In the study by Bian et al., participants seemed to assume that people

with very high intelligence are more likely to be males than females. The authors dismissed this

belief as a “negative stereotype about women”; they seemed unaware that males are in fact

overrepresented at the high end of the IQ distribution (as well as the low end; e.g., Arden &

Plomin, 2006; Johnson et al., 2008).

A fourth paper by Gruber et al. (2020) was a wide-ranging

analysis of gender gaps in academic psychology (e.g., career advancement, salary, grants,

publication and citation rates). This paper was noteworthy because it dismissed some robust

empirical patterns—men are overrepresented at the highest levels of cognitive ability, men are

more assertive and dominant, women are more communal—as mere stereotypes (see Del

Giudice, 2015; Twenge, 1997). The authors also embraced a socialization account of sex

differences, and rejected the possibility that some of them may have an adaptive explanation.

Of the remaining eleven papers, four took an explicitly evolutionary approach: a review

of men’s and women’s response to sexual versus emotional infidelity (Buss, 2018); a

comparative analysis of peer relationships in male and female humans vs. other primates

(Benenson, 2019); a paper on mitochondrial functioning as a mechanism for variation in general

intelligence, and a possible contributing factor to sex difference in variability (Geary, 2018); and

a conceptual paper on gender as the basis for social cognition (Martin & Slepian, 2020).

I completed this survey on November 9th, 2020, and included advance publication papers that were online at that

time.

One additional paper (Weberman & Murphy, 2020) offered recommendations to reduce “gender-based violence

and misconduct on college campuses”. Since this paper had a strictly applied focus and did not deal with basic

research on sex and gender, I excluded it from the survey.

The issue of greater male variability in intellectual abilities has a long and contentious history, which I address

later in the chapter.

More precisely, Martin and Slepian (2020) mixed ideas about evolved psychological mechanisms from

evolutionary psychology with the socialization account of social role theory (Eagly & Wood, 2012, 2016; see

below). The result is a strangely incoherent theory, according to which (a) humans possess evolved, deeply

Another experimental study (Treat et al., 2020) investigated men’s perception of women’s sexual

interest, but—surprisingly—failed to mention the substantial evolutionary literature on this topic

(e.g., Haselton, 2003; Haselton et al., 2016; Murray et al., 2017; Perilloux & Kurzban, 2015).

The final six papers were all meta-analyses or systematic reviews of sex differences. The

topics were episodic memory (Asperholm et al., 2019), student achievement in reading/writing

(Reilly et al., 2019), the initiation of negotiations (Kugler et al., 2018),

the development of

spatial reasoning (Lauer et al., 2019), the prevalence of mental disorders (Hartung & Lefler,

2019), and maternal reminiscing styles (differentiated by the child’s sex; Waters et al., 2019). Of

the meta-analyses that included a review of theoretical models, three considered both social and

biological explanations (Asperholm et al., 2019; Hartung & Lefler, 2019; Reilly et al., 2019),

while two only considered socialization effects (Kugler et al., 2018; Waters et al., 2019).

Once again, this brief survey of generalist journals reveals a fair amount of theoretical

diversity, but also a pervasive tendency to emphasize socialization over biology and downplay

robust empirical findings as “stereotypes”. Four out of 19 papers were motivated by the

transparently ideological project of challenging (and ultimately “disrupting”) the sex/gender

binary.

Among other things, this survey is a reminder of the continuing popularity of social role

theory (SRT; Eagly & Wood, 1999, 2012, 2016; Wood & Eagly, 2012) in the sex differences

literature. SRT played a major theoretical role in four of the papers (Gruber et al., 2020; Eagly et

al., 2020; Kugler et al., 2018; Martin & Slepian, 2020) and was cited in another four (Ellemers,

2018; Hyde et al., 2019; Morgenroth & Ryan, 2020; Reilly et al., 2019), for a total of eight

papers out of 19. (SRT was also cited in four of the seven introductory textbooks: Burton et al.;

Kalat; Noba Project; Schacter et al.) In a nutshell, the theory posits that evolved sex differences

in physical and reproductive traits (e.g., size, strength, pregnancy and lactation) have shaped the

division of labor between men and women throughout history (e.g., warfare vs. child-rearing). In

turn, the continued existence of sexually differentiated tasks has created powerful cultural

stereotypes about masculine and feminine traits, most notably along the axes of

dominance/agency vs. nurturance/communion. These stereotypes affect individual behavior

through socialization (partly via role-congruent activation of hormonal changes, for example in

testosterone and oxytocin levels), leading to the development of psychological differences

between the sexes.

ingrained, and stable gender schemas about typical masculine vs. feminine behaviors; but (b) masculine and

feminine behaviors themselves are mainly shaped by socialization, and malleable to the point that they can be

changed with subtle linguistic interventions (e.g., relabeling assertive and competitive behaviors from “masculine”

to “agentic” should help women become more competitive in the workplace).

The meta-analysis by Kugler et al. (2018) found that sex differences in the initiation of negotiation (a behavior

that is thought to contribute to gender inequalities) were “small” by conventional statistical criteria (for a detailed

critique of conventional criteria for effect sizes, see Del Giudice, 2020). As I noted above, this is usually a preferred

outcome—but not when differences are presented as evidence of discrimination. Indeed, the authors went to some

length to explain that even small effects can cumulate over time and give rise to large differences in outcomes—a

reasonable argument, but one that is rarely brought up in the literature on “gender similarities” (e.g., Hyde, 2005,

2014; but see Zell et al., 2015).

According to SRT, psychological sex differences are mostly constructed by socialization

practices, but the fact that they are ultimately grounded in evolved physical differences explains

their stability across time and cultures. From a biological standpoint, SRT is extremely

implausible, as it postulates an unexplained dualism between physical traits (subject to natural

and sexual selection) and psychological traits (more or less untouched by selection and only

shaped by socialization, either directly or indirectly via hormonal regulation).

Moreover, the

theory fails to explain why many sex differences become larger in more gender-egalitarian

cultures (see Friedman et al., 2000; Geary, 2021; Kenrick & Li, 2000; Schmitt, 2015). However,

SRT has proven quite attractive to social scientists, likely because it allows them to effectively

adopt a pure socialization perspective—and avoid inconvenient questions about evolved sex

differences “in the brain”—without appearing to reject evolutionary biology (see also Geary,

2021).

A Jump into the Time Warp

The received view on the history of sex and gender in psychology is nicely summarized

by this quote, from an article in the Monitor on Psychology announcing the APA’s new and

controversial “guidelines for psychological practice with boys and men”:

Prior to the second-wave feminist movement in the 1960s, all psychology was

the psychology of men. Most major studies were done only on white men and

boys, who stood in as proxies for humans as a whole. Researchers assumed that

In a recent video interview (October 10th, 2019; https://www.youtube.com/watch?v=gPsXpDIE0LA), Alice Eagly

claimed that she had never denied the existence of sexually selected differences in psychological traits, but had

simply chosen to emphasize the role of socialization. This is a transcript of the segment (starting at 17:56):

They [the evolutionary critics] put words in my mouth that I never said! I never said there

weren’t such influences. It’s merely that I emphasized others that they forget about. So I

would not claim that there are no such effects of prenatal androgenization or sexual selection

or whatever, but the force of my work has been to show that there are other influences, and

we need to get it all together.

This will come as a surprise to the many scholars who have used SRT precisely to discount the role of sexual

selection and other biological factors. But the interview does raise the question of what SRT actually says in this

regard. Re-reading the key papers presenting the theory, I could not find a single passage explicitly stating that

psychological sex differences can be explained by sexual selection, though I did find a number of passages

suggesting the opposite (e.g., Eagly & Wood, 1999, p. 415; Eagly & Wood, 2016, p. 464). Wood and Eagly (2012)

came closest to accepting an organizational role for prenatal androgens, but described the evidence as equivocal and

concluded that “[a]lthough sex-differentiated social experience surely does not operate on a blank slate, what is

written on that slate has not been adequately deciphered so far” (p. 67). Throughout the chapter, they discussed how

socialization may affect hormonal regulation, but not how hormonal differences may modulate social interactions

(note that, in their Figure 1, socialization factors affect hormonal regulation, but not vice versa). Similarly, Wood

and Eagly (2000) stated: “[…] we recognize that such biological factors [hormones] work in concert with

psychological processes involving social expectations and self-concepts to yield sex differences in behavior”, and

seemed to endorse “a feedback model in which testosterone affects socially dominant behavior and is in turn

affected by such behavior and its outcomes”. My conclusion is that Eagly and Wood hedged their bets on the role of

sex hormones; their writing on this issue invites a deflationary reading, but remains open to alternative

interpretations (see also Eagly, 2018). On the other hand, as far as I can tell these authors always portrayed SRT as

an alternative to sexual selection on psychological traits, rather than a complementary explanation.

masculinity and femininity were opposite ends of a spectrum, and “healthy”

psychology entailed identifying strongly with the gender roles conferred by a

person’s biological sex (Pappas, 2019, p. 35).

To call this a distorted account would be an understatement: as I show in this section, this

familiar narrative turns out to be an almost complete fabrication. I do not blame the author of this

quote, though; she simply distilled what can be found in ostensibly authoritative sources, such as

this chapter by Denmark et al. (2008) in the second edition of Psychology of women:

When one examines the psychological research from Wundt’s 1874

establishment of the domain of psychology up to recent times, psychology

appeared to focus almost exclusively on the behavior of men or male animals.

In other words, the first method of examining woman was to categorize them

as lacking. Much early research that included female subjects came to the

conclusion that women were inferior in some way. Additionally, if females

were included in the sample, neither sex nor gender differences were reported,

which discounted the influence of these factors and, in essence, was an

indication of the belief that men were the norm when considering various

psychological factors. And again, if women were included in the studies,

biased results indicated that women were by nature inferior. […] However,

generally speaking, most early research never investigated comparisons

between women and men at all (Schwabacher, 1972). Wendy McKenna and

Suzanne Kessler (1976) reported that over 95 percent of all early research did

not examine female-male comparisons, therefore ignoring any possible

differences due to sex and gender. Prior to the 1970s, almost all research on

women had been relegated to the periphery of psychology rather than

integrated into its main body. (Denmark et al., 2008, pp. 5-6).

The entire passage sounds immediately suspicious if one considers that, already in 1894,

Havelock Ellis could draw on dozens of studies of psychological sex differences for his

influential book Man and woman (more on this below). I was particularly struck by the blanket

statement about “over 95 percent of all early research”, so I looked up the original paper by

McKenna and Kessler (1977; the 1976 date in the quote is incorrect). To my (mild) surprise, the

actual study had little to do with the description. McKenna and Kessler did not analyze “all early

research” in psychology, but the latest 312 human experiments on interpersonal attraction and

244 on aggression, ending on December 1973. The authors did not report the date of the earliest

studies in the analysis, but it is unlikely that they went further back than 10-20 years.

They

I recommend the Denmark et al. chapter as a counterpoint to my “revisionist” account. For a less biased history of

the field, see Chapter 2 in Blakemore et al. (2009).

The authors checked 600 entries for each topic as reported in the Psychological Abstracts. Google Scholar returns

1,810 results for “interpersonal attraction” between 1953 and 1973 (searched on November 11, 2020). If one third of

them was reported in the Abstracts, that would amount to about 600 entries.

found that 38-45% of the studies included both males and females,

but did not say how many

of those studies involved comparisons between the sexes.

This is not an isolated case; feminist history is full of similar distortions and “urban

legends” that rarely get corrected from the inside. Notable examples include the claim that

women have been underrepresented as participants in medical research (Satel, 2002); that

biologists clung to the idea of sperm as active and “macho” and eggs as passive and “coy”

because of their sexist prejudices (Gross, 1998); that Victorian physicians used vibrators on

female patients to treat hysteria (Lieberman & Schatzberg, 2018); and that before World War II,

the color pink was associated with boys while blue was associated with girls (Del Giudice, 2012,

2017). The problem is not with feminism per se but with activist history in general; whatever the

virtues, an activist mindset is a major impediment to critical scrutiny and self-correction, and

encourages distortions in the service of the ideological narrative (Hoff Sommers, 2009).

Unfortunately, activist history is what one often gets when it comes to sex and gender. In the rest

of this section, I use citations from original sources to identify recurring themes and trace some

trends that go back more than a hundred years. Some of the quotes are lengthy, but I think it is

important to go beyond the soundbites and let the sources speak more freely.

The Dark Ages (Before the Sixties)

The best place to start may be the first edition of Havelock Ellis’ Man and woman (1894).

This book is a wide-ranging overview of sex differences and similarities in physical and

psychological traits. Considering that it was written more than 120 years ago, I think it has aged

remarkably well.

Throughout the book, Ellis took pains to acknowledge possible biases, strike

a balance between nature and nurture, and reject the idea of female (or male) inferiority. Here are

a few quotes that convey the spirit of the book:

It is also being recognised as reasonable that both sexes should study side by

side at the school and the college, and where not side by side, still in closely

similar fashion, while the recreations of each sex are to some extent becoming

common to both. Such conditions have tended to remove artificial sexual

differences, and have largely obliterated the coarser signs of superiority which

may before have been possessed by one sex over another. The process of

transition is still in rapid progress (Ellis, 1894, p. 17).

Combined data from Table 1 and Table 2 in McKenna and Kessler (1977).

McKenna and Kessler cited a paper by Carlson and Carlson (1960), who examined 298 human studies published

in the Journal of Abnormal and Social Psychology between 1958 and 1960. They found that 36% of the studies

included participants of both sexes, and that 30% of those studies reported statistical tests of sex differences. There

was no information about the proportion of studies that reported descriptive statistics for both sexes without

performing a test (and vice versa).

Needless to say, there are a lot of incorrect or outdated statements in the book, and some ideas of the time (e.g.,

the recurring distinction between “higher” and “lower” races) have definitely not aged well. But readers familiar

with current research on sex differences will be struck by how many issues Ellis managed to get approximately

right, despite the limited data and conceptual tools available at the time.

On biases in sex differences research:

We have to recognise, it will be seen, not merely the difficulties which come

from too small a number of observations, where we have the resource of

putting one series of observations against another, but also the more serious

difficulty of inevitable bias in the investigator's mind. […] Thus one

conscientious investigator (like Manouvrier) may find that all the facts of

anatomy and physiology point to the superiority of women; another, equally

conscientious (like Delaunay), may find that they all point to the superiority of

men (ibid., pp. 28-29).

On sex differences in brain anatomy:

While, however, the brain is at present an unprofitable region for the study of

sexual difference, it is, as we have seen, an extremely instructive region for

the study of sexual equality. Men possess no relative superiority of brain-

mass; the superiority in brain-mass, so far as it exists, is on woman's side;

this, however, implies no intellectual superiority, but is merely a characteristic

of short people and children. Nor is there any well-marked sexual arrangement

of the nervous elements which implies relative inferiority on one side or the

other (ibid., p. 113).

On sex differences in emotionality (discussed under the rubric of “affectability”):

The question still remains how far the affectability of women is natural and

organic, how far it is the mere accidental result of external circumstances. Is

the greater emotionality of women a permanent and ineradicable fact? There

can be no doubt that to a very large extent emotionality may be modified. […]

Just as we have sure reason to believe that sensibility may by training be

increased, so there is still greater reason to believe that affectability may by

training be decreased. That there is, however, a limit to this sexual

equalisation of affectability remains extremely probable. […] Affectability in

women may be reduced to finer and more delicate shades; it can scarcely be

brought to the male standard.

This result is by no means to be regretted. We have seen that the affectability

of women ensures to them certain solid advantages, and assists to safeguard

them against evils from which men are specially prone to suffer. (ibid., p. 313-

314).

Note that Ellis was talking about differences in relative brain mass, after adjusting for differences in body mass or

size. Ellis spent several pages (pp. 95-101) reviewing alternative ways to make this adjustment and considering their

limitations. In contrast with Ellis’ conclusions, the recent evidence shows that men have a larger brain even

controlling for body size (e.g., Ankney, 1992; Ritchie et al., 2018).

Neuroticism/Emotional stability is one of the personality traits showing the largest and most robust differences

between men and women. Sex differences become even larger in more gender-egalitarian countries, a finding that

would have surprised even Ellis (see MacGiolla & Kajonius, 2018; Schmitt et al., 2017).

On Darwin’s hypothesis of greater male variability:

Both the physical and the mental characters of men show wider limits of

variation than do the physical and mental characters of women. Monsters are

more often male than female. […] Abnormal variations of nearly all kinds are

more frequent in men than in women. […] We must regard genius as an

organic congenital abnormality (although the evidence in proof of this cannot

be entered into here), and in nearly every department it is, undeniably, of more

frequent occurrence among men than among women. The statement of this

fact has sometimes been regarded by women as a slur upon their sex; they

have sought to explain it by lack of opportunity, education, etc. It does not

appear that women have been equally anxious to find fallacies in the statement

that idiocy is more common among men. Yet the two statements must be

taken together. Genius is more common among men by virtue of the same

general tendency by which idiocy is more common among men. The two facts

are but two aspects of a larger zoological fact—the greater variability of the

male (ibid., p. 358-366).

And finally:

Any reader who has turned to this book for facts or arguments bearing on the

everlasting discussion regarding the “alleged inferiority of women,” and who

has followed me so far, will already have gathered the natural conclusion we

reach on this point. We may regard all such discussion as absolutely futile and

foolish. If it is a question of determining the existence and significance of

some particular physical or psychic sexual difference a conclusion may not be

impossible. To make any broad statement of the phenomena is to recognise

that no general conclusion is possible. Now and again we come across facts

which group themselves with a certain degree of uniformity, but as we

continue we find other equally important facts which group themselves with

equal uniformity in another sense. The result produces compensation (ibid.,

pp. 393-394).

One should remember that first-wave feminism was already ascendant at the end of the

19th century, and was going to intensify in the early decades of the 20th. A key representative of

this period was Helen Thompson Woolley, who in 1903 published The mental traits of sex, a

thorough experimental investigation of sex differences across dozens of tasks.

At the end of the

book, Woolley took issue with then-current biological explanations of sex differences

—

Unfortunately the sample was very small (25 men and 25 women), so the results were far less reliable than

assumed at the time. For example, Woolley failed to detect any sex differences in emotion-related measures, and

used this finding to argue that women’s higher emotionality was a baseless stereotype (see below).

In particular, Woolley criticized Geddes and Thomson’s (1889) theory of the evolution of sex, a then-popular

alternative to Darwin’s (1871) theory of sexual selection. Many biologists regarded sexual selection theory as

dubious until it was formalized by Fisher (1930); in the meantime, there were several attempts to develop an

alternative account of the evolution of males and females. Geddes and Thomson’s theory was one of those attempts,

including the hypothesis of greater male variability —and concluded with a plea for

environmental explanations:

The biological theory of psychological differences of sex is not in a condition

to compel assent. While it is true, therefore, that the present investigation

tends to support the theory, it is also true that the uncertain basis of the theory

itself leaves room for other explanations of the facts, if there are other

satisfactory ways of explaining them.

[…] Although the timeworn controversy is far from satisfactory settlement,

the results of recent observation of individual development have tended to

emphasize more and more the extreme importance of environment. […]

The fact that very genuine and important differences of environment do exist

can be denied only by the most superficial observer. Even in our country,

where boys and girls are allowed to go to the same schools and to play

together to some extent, the social atmosphere is different, from the cradle.

Different toys are given them, different occupations and games are taught

them, different ideals of conduct are held up before them. […]

It will probably be said that this view of the case puts the cart before the

horse—that the training and social surroundings of the sexes are different

because their natural characteristics are different. It will be said that a boy is

encouraged to activity because he is naturally active […] But there are many

indications that these very interests are socially stimulated. […]

There are, as everyone must recognize, signs of a radical change in the social

ideals of sex. The point to be emphasized as the outcome of this study is that,

according to our present light, the psychological differences of sex seem to be

largely due, not to difference of average capacity, nor to difference in type of

mental activity, but to differences in the social influences brought to bear on

the developing individual from early infancy to adult years. The question of

the future development of the intellectual life of women is one of social

necessities and ideals, rather than one of inborn psychological characteristics

of sex (Thompson, 1903, pp. 176-182).

Woolley’s book exemplifies some then-developing trends that have persisted to this day,

including the preference for socialization accounts and the diffidence toward biological

explanations. In 1910 and 1914, Woolley wrote two influential reviews of sex differences

research in the Psychological Bulletin. These reviews foreshadow other important themes—

including the growing emphasis on sex similarities within psychology, and the increasing

divergence between the findings of rigorous research and laypeople’s ideas about male and

female psychology. For example:

[T]here seems to be a general trend toward the opinion that mind is probably

not a secondary sexual character—in other words that there are probably few

if any psychological differences of sex which are of biological origin—a

statement which I think holds true in spite of the continued popularity of such

based on the opposition between anabolic and catabolic processes; in fairness to Woolley, there was plenty to be

critical about.

books as Mobius' Physiologischer Schwachsinn des Weibes and Weininger's

Geschlecht und Character. The tendency to minimize sexual differences is

most marked with regard to intellectual processes, the field where most of the

experimental work has been done, and in which the practical educational tests

have been made. Even the time-honored belief that men are more capable of

independent and creative work is beginning to give way in view of the

successful competition of women in graduate work and in obtaining the

doctorate [….] The fundamental importance of sexual differences in affective

processes and in standards of conduct still commands a larger measure of

credence. The world at large is quite agreed that women are to a greater extent

than men dominated by emotions, though the only direct experimental

evidence does not support this view […]

Finally, one might characterize the drift of recent discussion as a shift of

emphasis from a biological to a sociological interpretation of the mental

characteristics of sex. The very small amount of difference between the sexes

in those functions open to experimentation, the contradictory results obtained

from different series of investigations, and the nature of the differences which

prove to be most constant, have led to the belief that the psychological

differences of sex are of sociological rather than of biological origin

(Woolley, 1910, pp. 341-342).

In 1914, Woolley remarked that psychological research on sex differences was growing

so fast that it had become impossible to keep up with all the new literature:

During the four years since my last review of the literature of the psychology

of sex […] the number of experimental investigations in the field has

increased to such an extent that whereas it was difficult at that time to find

anything to review, it is now impossible to review all I could find (Woolley,

1914, p. 353).

Compare this statement with the narrative that “up to recent times, psychology appeared

to focus almost exclusively on the behavior of men or male animals,” or that “most early

research never investigated comparisons between women and men at all” (Denmark et al., 2008).

It can also be useful to stress that the psychologists of the 1910s were not simply concluding that

“women were by nature inferior”; on the contrary, Woolley (1910, 1914) listed several areas in

which women had been found to consistently outperform men, including aspects of perception,

memory, and reasoning.

Psychological research in Europe slowed down during World War I, but there were

enough studies to fill regular reviews in the Psychological Bulletin. Leta Hollingworth wrote a

series of those reviews in 1916, 1918, and 1919. A recurring theme was the variability

hypothesis, which Hollingworth herself had critiqued and researched (e.g. Hollingworth, 1914).

The data available at this point were contradictory, and opinions on the topic remained sharply

divided.

As I discuss later, the question of variability would take almost another hundred years

to be answered with confidence. This is how Hollingworth concluded her 1919 review:

The year's work yields nothing consistent as a result of the comparison of the

sexes in mental traits. In this respect it resembles the work of other years.

Pressey finds that girls excel boys in mental tests at all ages, from 8 to 16

years, inclusive; Porteus finds that boys excel girls at nearly all ages. Pressey

finds that boys are more variable than girls; Frasier finds that there are no sex

differences in variability. In group after group of superior children, the highest

intelligence is found now in a boy, now in a girl. Perhaps the logical

conclusion to be reached on the basis of these findings is that the custom of

perpetuating this review is no longer profitable, and may as well be

abandoned (Hollingworth, 1919, p. 373).

Like other feminist authors, Hollingworth was acutely skeptical of biological

explanations, and emphasized the role of environmental differences and the limitations imposed

by pregnancy and childcare. By then, this attitude was fairly widespread in academic circles. I do

not want to exaggerate the impact of egalitarian ideals on early 20th century psychology;

especially in applied areas such as clinical psychology and education, it is easy to find influential

works full of unsupported speculations about sex differences. A case in point is the often-quoted

Youth: its education, regimen, and hygiene by G. Stanley Hall (1906).

But I do want to

challenge the myth that academic psychology was indifferent or hostile to women until second-

wave feminism came about in the 1960s and 70s.

As literature reviews on sex differences continued to be published regularly, the concerns

of the field kept evolving. Allen (1927, 1930) noted the growing interest in sex hormones,

fostered by the striking advances in endocrinology that were taking place in the 1920s and 30s.

While the variability hypothesis was still debated, the prevailing opinion was that sex differences

are heavily influenced by environmental factors, and tend to be relatively small across the board.

Allen repeated the same conclusions in both his 1927 and 1930 reviews:

By way of summary, three points should be noted:

1. Few, if any, of the so-called “sex differences” are due solely to sex.

Individual differences often are greater than differences determined on the

basis of sex.

For example, Edward Thorndike was an early advocate of the hypothesis (Thorkdike, 1906); Lewis Terman

initially argued against it, but changed his mind in his later work (see McNemar & Terman, 1936; Terman et al.,

1946).

Then again, see Thorndike (1906) for a different perspective on the same issue.

Shields (1975) recounts the same period in the history of psychology, but from the standard feminist assumptions

that sex differences are largely socially constructed; that the variability hypothesis (like other biological

explanations) was only accepted because it justified women’s subordination; that the idea of an evolved “maternal

instinct” is nothing but a subtly oppressive fiction; etc. From this vantage point, everything looks much darker. But

even then, there is no ground for the narrative that “all psychology was the psychology of men”; and the

contributions of Hollingworth, Woolley, and other feminist psychologists were not marginalized, but published in

top journals, widely discussed, and accepted by many in the discipline.

2. The social training of the two sexes is, and always has been, different,

producing differential selective factors, interests, standards, etc.

3. The number of variables which either cannot or have not been controlled

hitherto make conclusions uncertain. Among other factors, a more careful

definition of terms is needed (Allen, 1927, p. 301).

Before moving on, I want to briefly discuss Terman and Miles’ (1936) seminal work on

masculinity-femininity (M-F) as a trait of individual variation. Terman and Miles measured M-F

as a bipolar construct, an idea that was to come under fire in the 1970s and be quickly

abandoned, only to be rediscovered in the 1990s (more on this below). The point I want to bring

up is that, contrary to the received view, discuss Terman and Miles did not equate mental health

with a rigid identification with one’s biologically prescribed role. Instead, they described

masculinity and femininity as continuous rather than mutually exclusive categories, and argued

that inflexible masculine/feminine roles take a toll on individuals and society:

Masculinity and femininity are important aspects of human personality. They

are not to be thought of as lending to it merely a superficial coloring and

flavor; rather they are one of a small number of cores around which the

structure of personality gradually takes shape. The masculine-feminine

contrast is probably as deeply grounded, whether by nature or by nurture, as

any other which human temperament presents. […] Whether it is less or more

grounded in general physiological and biochemical factors than these remains

to be seen. In how far the lines of cleavage it represents are inevitable is

unknown, but the possibility of eliminating it from human nature is at least

conceivable. The fact remains that the M-F dichotomy, in various patterns, has

existed throughout history and is still firmly established in our mores. In a

considerable fraction of the population it is the source of many acute

difficulties in the individual’s social and sexual adjustment and in a greater

fraction it affords a most important impetus to creative work and happiness.

The indications are that the present situation, together with the problems it

raises for education, psychology, and social legislation, will remain with us

for a long time to come.

As long as the child is faced by two relatively distinct patterns of personality,

each attracting him by its unique features, and is yet required by social

pressures to accept the one and reject the other, a healthy integration of

personality may often be difficult to achieve. Cross-parent fixations will

continue to foster sexual inversion; the less aggressively inclined males will

be driven to absurd compensations to mask their femininity; the more

aggressive and independent females will be at a disadvantage in the marriage

market; competition between the sexes will be rife in industry, in politics, and

in the home as it is today (Terman & Miles, 1936, p. 451-452).

This is what Terman and colleagues wrote ten years later:

Present-day concepts of sexuality no longer regard maleness and femaleness

as mutually exclusive categories. Sex is not an all-or-none affair; masculinity

and femininity are relative terms. […]

The biochemical forces which activate masculine and feminine behavior are in

some degree present in both sexes. […] As someone has stated it, there are no

men, there are no women; there are only sexual majorities (Terman et al.,

1946, p. 955).

With the rise and consolidation of behaviorism, the eclipse of evolutionary psychology at

the end of the 1930s (Gillette, 2007),

and the ebbing of fist-wave feminism, the 1940s and 50s

were relatively uneventful for sex differences research. The idea that popular stereotypes

exaggerate small and inconsequential differences persisted (e.g., Fernberger, 1948); other

scholars saw the possibility for a détente between nature and nurture:

For the present we may well avoid the extreme position common both among

laymen and scientists a generation ago, that nearly all sex differences are to be

accounted for in terms of original nature, and avoid equally the extreme

position which holds that the temperaments of men and women are no more

sex-determined than their clothing. Now that feminism is no longer a violent

issue, it is becoming possible to examine the picture of sex differences

unmoved by emotions deriving from sex rivalry. The physiologist has long

known that woman is something other than a wombed man, the social

psychologist is beginning to suspect it, and one dares look forward to a change

in the present-day bias of the cultural anthropologists (Johnson & Terman,

1940, p. 331).

All of this was going to change dramatically, starting with the late 1960s and culminating

in the 1970s; so this is where I go next.

The Seventies

The rise of second-wave feminism was not the only historical shift in the psychology of

the Seventies. There were also the decline of behaviorism and psychoanalysis; the situationist

turn in social and personality psychology; and the (attempted) resurrection of evolutionary

psychology on the wings of the sociobiological revolution (see Segerstråle, 2000). The mix was

explosive. The moment is best captured by Naomi Weisstein’s famous essay Psychology

constructs the female, first published in 1968:

It is an interesting but limited exercise to show that psychologists and

psychiatrists embrace these sexist norms of our culture, that they do not see

beyond the most superficial and stultifying media conceptions of female

nature, and that their ideas of female nature serve industry and commerce so

well. Just because it’s good for business doesn’t mean it’s wrong. What I will

Few know that the term “evolutionary psychology” was not coined in the 1990s (e.g., Barkow et al., 1992), but

was already in use in the late 19th and early 20th century. See for example Stanley (1895), Howard (1927), and

Jastrow (1927). For a historical overview see Gillette (2007).

show is that it is wrong: that there isn’t the tiniest shred of evidence that these

fantasies of servitude and childish dependence have anything to do with

women’s true potential; that the idea of the nature of human possibility which

rests on the accidents of individual development or genitalia, on what is

possible today because of what happened yesterday, on the fundamentalist

myth of sex organ causality, has strangled and deflected psychology so that it

is relatively useless in describing, explaining, or predicting humans and their

behavior. […]

[T]he evidence is collecting that what a person does, and who he believes

himself to be, will in general be a function of what people around him expect

him to be, and what the overall situation in which he is acting implies that he

is. Compared to the influence of the social context within which a person

lives, his or her history and “traits”, as well as biological makeup, may simply

be random variations, “noise” superimposed on the true signal which can

predict behavior.

[…] If subjects under quite innocuous and non-coercive social conditions can

be made to kill other subjects and other types of social conditions will

positively refuse to do so; if subjects can react to a state of physiological fear

by becoming euphoric because there is somebody else round who is euphoric

or angry because there is somebody else round who is angry; if students

become intelligent because teachers expect them to be intelligent, and rats run

mazes better because experimenters are told the rats are bright, then it is

obvious that a study of human behavior requires, first and foremost, a study of

the social contexts within which people move, the expectations as to how they

will behave, and the authority which tells them who they are and what they

are supposed to do. […]

Thus, for example, if out of two individuals diagnosed as having the

adrenogenital syndrome of female hermaphroditism, one is raised as a girl and

one as a boy, each will act and identify her/himself accordingly. The one

raised as a girl will consider herself a girl; the one raised as a boy will

consider himself a boy; and each will conduct her/himself successfully in

accord with that self-definition.

So, identical behavior occurs given different physiological states; and

different behavior occurs given an identical physiological starting point. So it

is not clear that differences in sex hormones are at all relevant to behavior.

[…]

But even for the limited function that primate arguments serve, the evidence

has been misused. Invariably, only those primates have been cited which

exhibit exactly the kind of behavior that the proponents of the biological basis

of human female behavior wish were true for humans. Thus, baboons and

rhesus monkeys are generally cited: males in these groups exhibit some of the

most irritable and aggressive behavior found in primates, and if one wishes to

argue that females are naturally passive and submissive, these groups provide

vivid examples. […] [I]n general, a counter-example can be found for every

sex-role behavior cited, including, as mentioned in the case of marmosets,

male “mothering” (Weisstein, 1971).

Thus, the feminist psychology of the Seventies recovered the classic themes of the earlier

decades (often without knowing; see Shields, 1975), but took them much further in a social

constructionist direction (see also Eagly, 2018; Eagly & Wood, 2013). The variability hypothesis

was seen as permanently discredited, and often brought up as an example of old-fashioned sexist

pseudoscience (e.g., Shields, 1975; Seller, 1981; Unger, 1979). The concept of gender

crystallized this attitude; to some scholars, it pointed to the socially constructed reality of

biological sex and the male-female binary:

Scientific knowledge does not inform the answer to the question: what makes

a person either a female or a male, a woman or a man? Rather, scientific

knowledge justifies, appears to give grounds for, and reflexively demonstrates

the already existing knowledge that a person is either a female or a male.

Biological, psychological and sociological differences do not lead to two non-

overlapping categories of people. Rather, the socially shared, common sense,

methodical construction of a world of two and only two genders leads to the

discovery of biological, psychological and sociological differences.

[…] Although it seems that the biological facts have an existence independent

of gender labels (there are XY chromosomes, etc. and all these together are

labeled “male”), the process, seen through the ethnomethodological approach,

is the reverse. […]

The role that biology plays in gender attribution is to provide “signs”, signs

which serve as good reasons for our attributions. […] In our culture,

biological facts give grounds for, and support, the facticity of two genders. At

the same time, biology is grounded in, and gets its support from, the basic

assumption that there are two, and only two, genders (McKenna, 1978, pp. 3-

8).

But these radical ideas were ahead of their time, and did not leave an enduring impression

on the discipline. Another flare was Sandra Bem’s work on androgyny and psychological

adjustment (Bem, 1974, 1975), which proved an empirical dead end and was soon attacked for

being insidiously sexist and male-centric (see Lippa, 2001). On the other hand, Bem’s argument

that masculinity and femininity are not the ends of a continuum, but rather independent

dimensions of behavior made a lasting contribution to the deconstruction of gender (see also

Constantinople, 1973). Also, from the ashes of androgyny rose gender schema theory (Bem,

1981), which is still a mainstream approach to the development of gender and gender identity

(see Blakemore et al., 2009; Liben, 2016).

In terms of staying power, the landmark contribution of this period was probably

Maccoby and Jacklin’s hugely influential book The psychology of sex differences (1974). The

authors collected and analyzed a large number of studies, and concluded that only four

differences could be regarded as well established, namely: males are more aggressive; females

excel in verbal ability; males excel in visuospatial ability; and males have superior mathematical

skills. They noted that the evidence was equivocal for sex differences in tactile sensitivity, fear

and anxiety, activity levels, competitiveness, dominance, compliance, and nurturant/“maternal”

behaviors; but dismissed sex differences in sociability, suggestibility, self-esteem, and a host of

other traits as “unfounded beliefs”. Also, they failed to find consistent evidence of differential

socialization in boys and girls, although this particular conclusion is often glossed over.

Maccoby and Jacklin’s book cemented the perception that, with very few exceptions,

laypeople’s ideas about male and female behavior are just groundless stereotypes:

How is it possible that people continue to believe, for example, that girls are

more "social" than boys, when careful observation and measurement in a

variety of situations show no sex difference? Of course it is possible that we

have not studied those particular situations that contribute most to the popular

beliefs. But if this is the problem it means that the alleged sex difference

exists only in a limited range of situations and the sweeping generalizations

embodied in popular beliefs are not warranted. […] A more likely explanation

for the perpetuation of “myths” we believe, is the fact that stereotypes are

such powerful things (Maccoby & Jacklin, 1974, p. 355).

The psychology of sex differences has been canonized as a careful, rigorous, even-handed

analysis of the literature of the time. In reality, it was a biased and surprisingly shoddy piece of

work. The authors failed to analyze many studies finding significant differences, even though

they had cited them in the bibliography; overinterpreted non-significant tests as evidence of no

difference, without taking into account statistical power and measurement reliability; largely

based their conclusions on studies of young children (12 years old or younger in 75% of the

studies); and dismissed several patterns indicative of sex differences with ad-hoc reasons. Block

(1976) discussed these problems in detail and reanalyzed Maccoby and Jacklin’s main findings,

reaching dramatically different conclusions. This did not prevent the book from becoming a

classic that is still cited to this day, often uncritically.

Where Are We? When Are We?

Almost fifty years and two waves of feminism later, what is the state of the field?

Evolutionary psychology is hopefully here to stay; but despite some attempts at reconciliation

(e.g., Buss & Schmitt, 2011; Campbell, 2006; Nicolas & Welling, 2015) and the contributions of

scholars with a distinct feminist perspective (e.g., Fisher et al., 2013; Hrdy, 2009), it continues to

attract harsh criticism by feminists outside the field (e.g., Barnett & Rivers, 2004; Fausto-

Sterling, 1992, 2000; Fine, 2017; McCaughey, 2007; Saini, 2017). A coherent evolutionary

approach challenges every single one of the preferences that inform the psychology of sex and

gender, so there is no resolution in sight. Social role theory is a false compromise, and while I

suspect that it will remain popular for some time, it cannot provide the needed common ground

(see also Geary, 2021). Like a hundred years ago, sexual selection is the main target of feminist

critiques, not just in psychology (e.g., Fine, 2017; Tavris, 1992) but also in anthropology and

biology (e.g., Dunsworth, 2020; Fausto-Sterling, 1992; Roughgarden, 2013; see Hankinson

Nelson, 2017). Since the basic logic of sexual selection seems to be essentially correct, but most

feminists cannot bring themselves to accept it (Vandermassen, 2004), the debate does not

advance and it’s déjà vu all over again.

In the meantime, the variability hypothesis—a “pernicious hypothesis” for Noddings

(1992), a “social Darwinist myth” for Denmark et al. (2008)—has been largely confirmed across

species (Reinhold & Engqvist, 2013; Wyman & Rowe, 2014). In humans, larger samples and

better analytical techniques have shown that males are systematically more variable than

females, both in general intelligence (indexed by IQ) and in most specific cognitive skills (e.g.,

Arden & Plomin, 2006; Baye & Monseur, 2016; Feingold, 1992; He & Wong, 2011; Johnson et

al., 2008; Lohman & Lakin, 2009; Machin & Pekkarinen, 2008). The same applies to many

physical and physiological traits (Lehre et al., 2009). In the domain of personality, men’s scores

also tend to be somewhat more variable; the main exception is neuroticism/emotional stability,

which shows significantly higher variability in women (see Del Giudice, 2015, 2020; Del

Giudice et al., 2018b). Empirical confirmation has not made the hypothesis less incendiary,

however. Both Larry Summers (former President of Harvard; see Taylor, 2005) and James

Damore (see Anomaly & Winegard, 2019) were ostracized for mentioning greater male

variability, among other things; in 2017, a mathematical paper that discussed the logic of the

hypothesis (Hill, 2017) was immediately “un-published” after controversy erupted (see Hill,

2018). As I noted earlier, it is still quite possible to publish in top psychology journals without

acknowledging the evidence of higher male variability in intellectual abilities.

In psychology, the landmark work of the 2000s was surely Janet Hyde’s (2005) paper on

the gender similarities hypothesis, or the hypothesis that “‘males and females are similar on

most, but not all, psychological variables. That is, men and women, as well as boys and girls, are

more alike than they are different.” (Hyde, 2005, p. 581). This had also been the message of

Maccoby and Jacklin’s book, so what was new? First, Hyde relied on data from large meta-

analyses instead of individual studies. And second, she used conventional thresholds to sort sex

differences into “trivial”, “small”, “moderate”, and “large”.

On the positive side, the paper highlighted the importance of quantification, and

demonstrated the potential of integrating data on a large scale. But the idea of interpreting sex

differences automatically and out of context, based on meaningless conventional thresholds, was

deeply unfortunate (for extended discussion of why this is the case, see Del Giudice, 2020; Hill

et al., 2008). In all likelihood, the paper’s visibility has contributed to entrench this mechanical

practice even deeper in the literature (e.g., Zell et al., 2015); to illustrate, three of the meta-

analyses I surveyed for this chapter interpreted their findings based on the same thresholds

(Kugler et al., 2018; Lauer et al., 2019; Reilly et al., 2019). Other limitations of Hyde’s approach

include averaging functionally distinct traits within the same category, neglecting measurement

error, and failing to consider that differences can cumulate across traits yielding large

multivariate distances between male and female profiles (see Del Giudice, 2020; Del Giudice et

al., 2012). Be as it may, the conclusion that most sex differences are trivial to small struck a

chord, and the paper has become a standard reference in the literature on gender stereotypes

(e.g., Ellemers, 2018).

As an aside, Hyde (2005, 2014) recognized that trait variability is often higher in males,

even though she downplayed the practical significance of this finding and emphasized the

context-dependence of sex differences. In Hyde’s view, it is not only laypeople who are victim

of inflated stereotypes, but also scientists—and they should stop caring so much:

When researchers find a gender difference, they might productively ask

themselves, is this important, and why is it important? Are other issues more

important?

Nonetheless, research on psychological gender differences will continue for

years to come, given many scientists’ firm beliefs that such differences exist

and are large and the media’s insatiable thirst for new findings of gender

differences (Hyde, 2014, p. 3.21).

This attitude toward sex differences in fairly common in the psychological literature. The

underlying assumption is that “stereotypes” of large and/or stable sex differences are harmful,

both to individuals and society at large (e.g., Barnett & Rivers, 2004; Ellemers, 2018; Gruber et

al., 2020; Hyde, 2005, 2014). For example:

It is time to consider the costs of overinflated claims of gender differences.

Arguably, they cause harm in numerous realms, including women’s

opportunities in the workplace, couple conflict and communication, and

analyses of self-esteem problems among adolescents (Hyde, 2005, p. 590).

I do not dispute that exaggerating sex differences, and depicting them as overly rigid and

inflexible, can cause all sorts of problems. But the converse is also obviously true: if there are

some meaningful and robust sex differences, minimizing or denying them can be just as

harmful—for example by distorting people’s understanding of themselves and others, hindering

communication between partners and on the workplace, reducing the effectiveness of

psychotherapy, and encouraging the adoption of unrealistic or counterproductive policies. The

virtually complete neglect of these potential risks—in the face of constant alarm about the

dangers of exaggerated stereotypes—is one of the clearest manifestations of ideological bias in

this area of research.

The other major theme I have discussed is the deconstruction of gender and sex. Starting

from the 1990s, the idea that masculinity and femininity are independent dimensions of variation

has been challenged by research showing that, even if M-F is not a simple unitary construct, it is

possible to derive robust and meaningful M-F dimensions from patterns of interest and

personality (see Lippa, 2001, 2010; Del Giudice, 2020). The more radical project of disrupting

the “sex binary” started in the 1970s and was still underway in the 1990s (e.g., Fausto-Sterling,

1993), but did not start to get serious traction until the mid-2010s, when it merged with fourth-

wave feminism and transgender activism. It is still too early to know how psychology will be

impacted, but I suspect that future (re)incarnations of this chapter will have an interesting story

to tell.

The Other Side of Bias

Before ending this exploration, it is important to consider the possible influence of other

kinds of ideology besides feminism and egalitarianism. The polar opposite of cosmic

egalitarianism is anti-egalitarianism—the belief that groups are naturally unequal, with

“superior” groups that deserve to win and dominate, and “inferior” ones that deserve to lose and

be dominated. Psychologically, this perspective aligns with the trait known as social dominance

orientation (SDO; see Pratto et al., 1994). I’m not sure if I have ever talked to a single

psychologist who held such an anti-egalitarian worldview. On the other hand, plenty of

psychologists do not subscribe to cosmic egalitarianism and believe that there are robust—

though not necessarily fixed—differences between males and females, which are rooted in our

evolutionary history and not primarily caused by socialization. In the feminist literature, this is

called “gender essentialism” and viewed as a set of defensive beliefs whose function is to resist

social change, foster acceptance of (socially constructed) sex differences, and legitimize the

status quo (e.g., Morton et al., 2009; Skewes et al., 2018; Wood & Eagly, 2012).

Naturally, the notion that the status quo is by definition unjust and in need of radical

transformation is debatable—unless, of course, one is already an activist. And if one takes an

activist perspective, the only real explanation for disagreement becomes ideological opposition,

with the result that legitimate scientific debates get routinely recast as ideological ones.

Reflecting on the influence of feminism in psychology, Eagly (2018) remarked that “ideology is

the most difficult of biases to erase because its advocates seldom recognize or acknowledge it”

(p. 12). To me, this seems disingenuous: throughout history, feminist scholars have openly

acknowledged their ideological motivations and often embraced them with pride.

The

ideological roots of feminist research are anything but hidden or implicit; the notion that “we are

all ideologically biased” has a kernel of truth, but should not be used to suggest false

equivalences between approaches that strive to minimize bias and those that seek to amplify it

(see Tybur & Navarrete, 2018).

That said, the empirical data do indicate that “gender essentialist” beliefs tend to correlate

with more conservative politics and higher SDO in the general population (Skewes et al., 2018).

Also, perceiving larger differences between the sexes predicts stronger endorsement of so-called

“sexist” beliefs (Zell et al., 2016)—although the latter mainly consist of being critical of

feminism, attributing certain positive/negative qualities to women (e.g., good taste, being easily

offended), and expressing protectiveness or romantic admiration.

The assumption that

“essentialist” ideas about sex differences point to a hidden conservative agenda may explain why

To give just one example, Else-Quest and Hyde (2018) advocate a feminist approach to psychology, and clearly

note that “[f]eminism is a political movement and ideology as well as a theoretical perspective” (p. 7).

In fact, the questionnaire that is commonly used to measure sexism (the “ambivalent sexism inventory”; Glick &

Fiske, 1996) is a textbook example of blatant ideological bias in psychology. Here are some sample items indicating

“benevolent sexism”:

- In a disaster, women ought not necessarily to be rescued before men (reverse-scored).

- Women, as compared to men, tend to have a more refined sense of culture and good taste.

- Women, compared to men, tend to have a superior moral sensibility.

- No matter how accomplished he is, a man is not truly complete as a person unless he has the love of a

woman.

And some examples of “hostile sexism”:

- Feminists are making entirely reasonable demands of men (reverse-scored).

- Many women are actually seeking special favors, such as hiring policies that favor them over men, under

the guise of asking for “equality.”

- Women are too easily offended.

- Most women interpret innocent remarks or acts as being sexist.

The last item is especially ironic, considering that the questionnaire is full of arguably innocent remarks that are

interpreted as indicators of sexism.

academics who are more liberal (in the sense of left-wing) tend to view evolutionary psychology

with more skepticism (Buss & von Hippel, 2018, Jonason & Schmitt, 2016; see also Tybur &

Navarrete, 2018). As it turns out, however, evolutionary psychologists and anthropologists are

just as left-wing as their non-evolutionary colleagues (Lyle & Smith, 2012; Tybur et al., 2007).

Almost all my colleagues who study sex differences from a biological perspective are politically

liberal, and in favor of equalizing opportunities and conditions between the sexes as much as

possible. This does not mean that subtle biases and distortions cannot happen; but the suspicion

that evolutionary psychologists as a group are motivated by right-wing or anti-egalitarian

concerns has no basis in reality.

More generally, the traditions and theoretical commitments of a field can easily create

biases that, even if not “ideological” in a strong sense, end up distorting the science produced

within that field. For example, the evidence for “human universals” has played a crucial role in

lending credibility to evolutionary psychology (see Pinker, 2003). Even if cross-cultural

variation is a major topic of research (e.g., Chapais, 2017; Gangestad et al., 2006; Schmitt, 2015;

Schmitt et al., 2017), the field as a whole may be unduly biased in favor of constancy and

universality, at the risk of discounting change and variability. On the issue of sex and gender,

bias can take the form of exaggerating sex differences, downplaying the flexibility of sex roles in

humans and other animals, and focusing too much on women’s attractiveness and mating while

neglecting parenting and post-reproductive behavior (see e.g., Burch, 2020; Eagly & Wood,

2013; Fischer et al., 2013; Stewart-Williams & Thomas, 2013). While the sex binary (properly

understood) is not a myth to dispel but a fundamental biological reality, it is true that differences

and variation in gender identity have not received the attention they deserve from evolutionists. I

also think that evolutionary psychologists could do a better job of communicating the nuance of

their theories and findings to the public, for example by putting more emphasis on within-sex

variation and context-dependence. As usual, the best antidote to bias is open conversation (see

Del Giudice et al., 2018a; Fine et al., 2018; Fine, 2020; von Hippel et al., 2020). The worst

aspect of pervasive ideology is the way in which it suppresses dialogue, and ensures that some

ideas will not be heard and discussed.

Conclusion: What’s Next?

This is the point in the chapter where one looks at the future to offer suggestions and

advice. I am writing this chapter at the end of 2020, as political/ideological tensions in the USA

and other Western countries are reaching a peak of intensity. This may be just about the worst

possible time to make predictions; but some trends seem reasonably clear, and do not make me

optimistic in the short run. At least for a while, egalitarian and anti-biological biases in

psychology are going to get stronger, making universities and academic journals more hostile

toward the “wrong” kind of research. Anecdotes from colleagues and in the news suggest that

academic censorship is tightening, both before publication (ethical reviews, journal reviews,

editorial decisions) and after (retraction campaigns; e.g., Reynolds, 2020). Even teaching about

certain sex differences is becoming difficult or impossible; the speech codes of many universities

To be clear, I do not think this is necessarily a good thing. While evolutionary psychology may be quite effective

at limiting the impact of researchers’ ideological biases (thanks to the “buffering” effect of strong theory; Tybur &

Navarrete, 2018), more political diversity would almost certainly benefit the field, and add another layer of

protection against conformity and groupthink.

now proscribe “gender harassment”, an ill-defined concept that can be expanded to include any

form of unwelcome “stereotyping” (e.g., Leskinen et al., 2014). On the positive side, researchers

have the option to reach the broader public through online videos, podcasts, blogs, and

magazines, effectively creating a sort of academic counterculture. While this is not ideal (and

online channels are also vulnerable to censorship), it may help the field survive a spell of

ideological suppression. Another reason for hope is that large, information-rich datasets (often

from multiple countries) are becoming increasingly common and easy to access. In this sense,

there has never been a better time to study sex differences and similarities; even in a worsening

ideological climate, I expect to see a lot of exciting new research—both by academics and by

independent researchers.

Is there anything that can be done right now to mitigate bias? As I noted earlier,

conversations across scientific/ideological barriers are extremely important and should be

encouraged whenever possible. Recently, noted feminist psychologist Alice Eagly argued that

her colleagues should break with a tradition of diffidence, and start considering how biological

influences contribute to shape behavior in males and females (Eagly, 2018). Unfortunately,

mainstream feminism is moving fast in the opposite direction; also, some of the issues at stake

(e.g., the role of sexual selection) have been contentious for more than a century—a fact that

does not inspire hope for a resolution (Vandermassen, 2020). On the other hand, it is possible

that more scholars will become frustrated with the growing polarization in their field, and begin

to seek dialogue with “moderates” on the other side of these issues. Facilitating these exchanges

should become a priority for non-partisan organizations, societies, and journals.

After spending some time on textbooks, I believe there are many untapped opportunities

to combat bias at the level of introductory courses. A slanted introduction to the field—one that

ignores or downplays sex differences, and fails to provide the conceptual tools to make sense of

them—can leave a lasting impression that is hard to correct later on (if it gets corrected at all).

One option for sex differences researchers is to contact the authors of popular textbooks to offer

feedback, advice, and links to useful teaching materials (e.g., videos, interviews, exchanges

between researchers with different viewpoints). Another option would be to produce brief

“supplements”, written in a textbook style and designed to balance out the standard narrative that

students are likely to encounter. Supplements of this kind could be easily made available online,

and disseminated via social media and other channels (the same approach might work for other

topics covered in this volume). There are probably many other ways to improve the curriculum

and give students a fuller picture of the field, while avoiding the pressures and compromises

faced by textbooks authors and course instructors.

As I have stressed through the chapter, ideological biases in the psychology of sex and

gender are deeply entrenched, and as old as the discipline itself. Whatever happens in the next

years, quick and simple fixes are not going to work; making real progress will require courage,

patience, focused effort—and all the creativity we can muster.

Acknowledgments

Warm thanks to Romina Angeleri, Mike Bailey, David Geary, and Richard Lippa for

their helpful and constructive comments.

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The S-Index: Summarizing Patterns of Sex Differences at the Distribution Extremes

Article

Full-text available

Jan 2023
PERS INDIV DIFFER

Marco Del Giudice

Sex differences researchers are becoming increasingly interested in how differences in averages and variability jointly influence male and female representation at the tails of the distribution. This paper introduces the S-index, a novel index that provides a simple and robust summary of the shape of sex differences at the distribution extremes. The use of S is illustrated with a selection of real-world datasets of personality and cognitive ability, and a R function is provided to calculate S and draw intuitive proportion plots of sex differences across the distribution. The S-index is not limited to the study of sex differences; it can be applied to other domains as long as the groups to be compared are about equally represented in the population and the variables of interest are approximately bell-shaped.

Sex differences and occupational choice Theorizing for policy informed by behavioral science

Article

Oct 2022
J ECON BEHAV ORGAN

Occupations are segregated with respect to sex, even in modern, egalitarian societies. There are strong pressures to eliminate segregation and therefore strong reasons to correctly theorize why segregation persists. The dominant view underpinning most public policies is essentially that environmental factors nudge women and men into different occupational paths. Nudging, however, ignores research suggesting that psychological traits that influence occupational choice differs between women and men, on average. Some of the most well-documented and persistent average sex differences between men and women suggest that the taken-for-granted assumption that an egalitarian society would exhibit a more or less equal distribution of men and women across the occupational landscape may be mistaken. Rather, models of occupational choice informed by individual differences in preferences, broadly understood, would help us better explain how men and women behave in the labor market. Differences in occupational preferences will affect choices. Therefore, differences in proportions of women and men across professions may be in line with an egalitarian society and the well-being and best interest of both men and women in society.

Female bisexuality

Preprint

Full-text available

Dec 2020

Bisexual behavior is an order of magnitude more common than exclusive homosexuality in women. Many evolutionary hypotheses on sexual orientation have focused on homosexuality, particularly in men, yet there has recently been a growing recognition that male and female homosexuality may have different evolutionary origins, and that the various forms of nonheterosexuality in the female sexual orientation spectrum may arise via discrete evolutionary–developmental mechanisms. Evolutionarily informed sex research therefore has the fascinating task of understanding the whole spectrum of female sexual orientation — from heterosexual, mostly heterosexual, and bisexual women through to exclusively homosexual women, and from feminine femmes to masculine butches — including the proximate mechanisms and ultimate functions that underlie that variation. Here, we address that task by applying Tinbergen’s four questions to analyze female bisexuality, synthesizing existing research on proximate mechanisms, ontogeny, phylogeny, and ultimate functions. Research in psychology and behavioral sciences indicates that bisexual women comprise a group distinct from heterosexual women and, on some metrics, even from lesbian women: bisexual women have more male-typical personality traits, more unrestricted sociosexual attitudes and behaviors, higher sexual responsiveness, earlier reproduction, higher substance use, higher incarceration rates, and worse health outcomes than heterosexual women. There is broad evidence from across mammalian species which indicates that individual differences in prenatal exposure to sex hormones creates individual differences in brain morphology, cognition, behavioral predispositions, and even life outcomes. They are typically studied in a sex differences framework, but there is now enough evidence to suggest that sexual orientation differences along these parameters can also be robust and informative. We review 10 ultimate-level hypotheses on the evolution of female bisexuality and conclude that four hypotheses — balanced polymorphism of masculinity, sexually antagonistic selection, hormonally mediated fast life history strategy, and byproduct — are currently best supported by evidence. These hypotheses are also consilient with the wealth of neurodevelopmental evidence on the masculinization of the brain and behavior which is thought to underlie variation in female sexual orientation. By synthesizing ultimate functions with proximate mechanisms — combined with powerful mid-level frameworks such as life history theory — evolutionary scientists are in a stronger position to provide a comprehensive account of the phenotypic variation observed in the female sexual orientation spectrum.

Extensions of Sexual Strategies Theory across Peoples, Cultures, and Ecologies

Chapter

Jan 2023

David P. Schmitt

The Oxford Handbook of Human Mating covers the contributions and up-to-date theories and empirical evidence from scientists regarding human mating strategies. The scientific studies of human mating have only recently risen, revealing fresh discoveries about mate attraction, mate choice, marital satisfaction, and other topics. Darwin’s sexual selection theory primarily guides most of the research in the scientific study of mating strategies. Indeed, research on the complexities of human mate competition and mate choice has centred around Darwin’s classic book. This book discusses theories of human mating; mate selection and mate attraction; mate competition; sexual conflict in mating; human pair bonding; the endocrinology of mating; and mating in the modern world.

4 - Female Bisexuality

Article

Jun 2022

Todd K Shackelford

Bisexual behavior is an order of magnitude more common than exclusive homosexuality in women. Many evolutionary hypotheses on sexual orientation have focused on homosexuality, particularly in men, yet there has recently been a growing recognition that male and female homosexuality may have different evolutionary origins, and that the various forms of nonheterosexuality in the female sexual orientation spectrum may arise via discrete evolutionary–developmental mechanisms. Evolutionarily informed sex research therefore has the fascinating task of understanding the whole spectrum of female sexual orientation – from heterosexual, mostly heterosexual, and bisexual women through to exclusively homosexual women, and from feminine femmes to masculine butches – including the proximate mechanisms and ultimate functions that underlie that variation. Here, we address that task by applying Tinbergen’s four questions to analyze female bisexuality, synthesizing existing research on proximate mechanisms, ontogeny, phylogeny, and ultimate functions. Research in psychology and behavioral sciences indicates that bisexual women comprise a group distinct from heterosexual women and, on some metrics, even from lesbian women: bisexual women have more male-typical personality traits, more unrestricted sociosexual attitudes and behaviors, higher sexual responsiveness, earlier reproduction, higher substance use, higher incarceration rates, and worse health outcomes than heterosexual women. There is broad evidence from across mammalian species that indicates that individual differences in prenatal exposure to sex hormones creates individual differences in brain morphology, cognition, behavioral predispositions, and even life outcomes. They are typically studied in a sex differences framework, but there is now enough evidence to suggest that sexual orientation differences along these parameters can also be robust and informative. We review ten ultimate-level hypotheses on the evolution of female bisexuality and conclude that four hypotheses – balanced polymorphism of masculinity, sexually antagonistic selection, hormonally mediated fast life history strategy, and by-product – are currently best supported by evidence. These hypotheses are also consilient with the wealth of neurodevelopmental evidence on the masculinization of the brain and behavior, which is thought to underlie variation in female sexual orientation. By synthesizing ultimate functions with proximate mechanisms – combined with powerful mid-level frameworks such as life history theory – evolutionary scientists are in a stronger position to provide a comprehensive account of the phenotypic variation observed in the female sexual orientation spectrum.

Fairly Criticized, or Politicized? Conflicts in the Neuroscience of Sex Differences in the Human Brain

Article

Dec 2021

Cordelia Fine

Investigations of sex differences in the human brain take place on politically sensitive terrain. While some scholars express concern that gendered biases and stereotypes remain embedded in scientific research, others are alarmed about the politicization of science. To help better understand these debates, this review sets out three kinds of conflicts that can arise in the neuroscience of sex differences: academic freedom versus gender equality; frameworks, background assumptions, and dominant methodologies; and inductive risk and social values. The boundaries between fair criticism and politicization are explored for each kind of conflict, pointing to ways in which the academic community can facilitate fair criticism while protecting against politicization.

The Future of Women in Psychological Science

Article

Full-text available

Sep 2020
PERSPECT PSYCHOL SCI

There has been extensive discussion about gender gaps in representation and career advancement in the sciences. However, psychological science itself has yet to be the focus of discussion or systematic review, despite our field's investment in questions of equity, status, well-being, gender bias, and gender disparities. In the present article, we consider 10 topics relevant for women's career advancement in psychological science. We focus on issues that have been the subject of empirical study, discuss relevant evidence within and outside of psychological science, and draw on established psychological theory and social-science research to begin to chart a path forward. We hope that better understanding of these issues within the field will shed light on areas of existing gender gaps in the discipline and areas where positive change has happened, and spark conversation within our field about how to create lasting change to mitigate remaining gender differences in psychological science.

The Effects of Gender Trouble: An Integrative Theoretical Framework of the Perpetuation and Disruption of the Gender/Sex Binary

Article

Full-text available

May 2020

In the Western world, gender has traditionally been viewed in the Western world as binary and as following directly from biological sex. This view is slowly changing among both experts and the general public, a change that has been met with strong opposition. In this article, we explore the psychological processes underlying these dynamics. Drawing on previous work on gender performativity as well as gender as a performance, we develop a psychological framework of the perpetuation and disruption of the gender/sex binary on a stage that facilitates and foregrounds binary gender/sex performance. Whenever character, costume, and script are not aligned the gender/sex binary is disrupted and gender trouble ensues. We integrate various strands of the psychological literature into this framework and explain the processes underlying these reactions. We propose that gender trouble can elicit threat—personal threat, group-based and identity threat, and system threat—which in turn leads to efforts to alleviate this threat through the reinforcement of the gender/sex binary. Our framework challenges the way psychologists have traditionally treated gender/sex in theory and empirical work and proposes new avenues and implications for future research.

Bashful Eggs, Macho Sperm, and Tonypandy Paul R. Gross

Chapter

Sep 1998

Paul A. Gross

The interdisciplinary enterprise of Science, Technology and Society Studies (STS) fosters the view that the results of scientific inquiry are social constructions that are strongly influenced by ideology and special interests. Academics working within traditions of postmodernism and cultural studies use both theoretical analysis and historical case studies to defend their allegations that the objectivity and empirical character of science have been vastly overrated. This anthology, with essays by philosophers, historians, scientists, and engineers, scrutinizes these claims in detail. Inspired by the Sokal hoax, these essays provide devastating refutations of the most central and widely trumpeted claims of the postmodernist critique of science. Included are clear analyses of philosophical concepts such as relativism, theory ladenness, underdetermination of theory by evidence, scientific experimentation, objectivity, the context of discovery, the role of metaphors in science, and sociology of scientific knowledge. The historical episodes discussed come from alchemy, the Scientific Revolution, Darwinian evolutionary theory, reproductive biology, particle physics, fluid mechanics, relativity theory, and statistics. Implications are drawn for science education, science journalism, science development, and the historiography of science.

A failure of academic quality control: The technology of orgasm

Article

Aug 2018

The Technology of Orgasm by Rachel Maines is one of the most widely cited works on the history of sex and technology. Maines argues that Victorian physicians routinely used electromechanical vibrators to stimulate female patients to orgasm as a treatment for hysteria. She claims that physicians did not perceive the practice as sexual because it did not involve vaginal penetration. The vibrator was, according to Maines, a labor-saving technology to replace the well-established medical practice of clitoral massage for hysteria. This argument has been repeated almost verbatim in dozens of scholarly works, popular books and articles, a Broadway play, and a feature-length film. Although a few scholars have challenged parts of the book, no one has contested her central argument in the peer-reviewed literature. In this article, we carefully assess the sources cited in the book. We found no evidence in these sources that physicians ever used electromechanical vibrators to induce orgasms in female patients as a medical treatment. The success of Technology of Orgasm serves as a cautionary tale for how easily falsehoods can become embedded in the humanities.

Sex Differences: Summarizing More than a Century of Scientific Research

Book

May 2013

Tracking Men’s Perceptions of Women’s Sexual Interest

Article

Feb 2020

Judging a woman’s current sexual interest in a specific man is a socially and emotionally complex decision. These judgments can be considered a form of perceptual decision-making in which men integrate both affective (emotional) and nonaffective cues. College men at risk of sexual aggression rely less on women’s affective cues and more on nonaffective cues, suggesting that cognitive processes may matter for real-world problems. However, in the real world, people may not have the luxury of waiting for processes to complete before they act. Recent work has used dynamic-competition models of decision-making to examine this problem. These models assume that affective judgments (such as interested vs. rejecting) are partially activated by multiple cues and compete over time. This work, in which mouse tracking is used to index partial decision states, demonstrates that on-line measures predict rape-supportive attitudes over and above off-line (judgment) measures. This offers a new way to understand the cognitive core of an important societal problem.

How Can Psychology Help Reduce Gender-Based Violence and Misconduct on College Campuses?

Article

Sep 2020
AM PSYCHOL

Psychological research has been at the forefront of efforts to document, understand, and prevent sexual harassment, sexual coercion, sexual violence, and intimate partner abuse on college campuses. Collectively, these various forms of gender-based violence and misconduct (GBVM) are highly prevalent on college campuses and exert wide-ranging negative effects on students' mental health and academic success. A recent resolution by the American Psychological Association outlined the field's research contributions and ongoing commitment to help prevent campus sexual assault. Our article builds on this initiative by offering 10 recommendations to psychology researchers, educators, and practitioners to address critical gaps in GBVM knowledge and practice through novel applications of psychology. These recommendations include: (a) Develop interventions to reduce and prevent faculty-perpetrated GBVM; (b) encourage and support professional sanctions for credibly accused faculty perpetrators of GBVM; (c) explore alternative models of graduate student mentorship; (d) develop improved risk prediction models for GBVM perpetration; (e) enhance selective and indicated prevention focused on individual and contextual risk; (f) support improvements in institutional responses to Title IX cases; (g) study the experiences and needs of student populations traditionally underrepresented in GBVM research, including racial/ethnic minority, sexual minority, and religious minority students, international students, and returning (nontraditional) students; (h) refine and disseminate campus interventions to promote relationship skill development; (i) refine and disseminate classroom-based prevention models; and (j) train and support the next generation of antiviolence scholars, clinicians, educators, and activists. Illustrative examples of these ongoing efforts are provided throughout the article and within a summary table. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The Primacy of Gender: Gendered Cognition Underlies the Big Two Dimensions of Social Cognition

Article

Jun 2020

It is notable that across distinct, siloed, and disconnected areas of psychology (e.g., developmental, personality, social), there exist two dimensions (the “Big Two”) that capture the ways in which people process, perceive, and navigate their social worlds. Despite their subtle distinctions and nomenclature, each shares the same underlying content; one revolves around independence, goal pursuit, and achievement, and the other revolves around other-focus, social orientation, and desire for connection. Why have these two dimensions emerged across disciplines, domains, and decades? Our answer: gender. We argue that the characteristics of the Big Two (e.g., agency/competence, communion/warmth) are reflections of psychological notions of masculinity and femininity that render gender the basis of the fundamental lens through which one sees the social world. Thus, although past work has identified the Big Two as a model to understand social categories, we argue that gender itself is the social category that explains the nature of the Big Two. We outline support for this theory and suggest implications of a gendered cognition in which gender not only provides functional utility for cognitive processing but simultaneously enforces gender roles and limits men and women’s opportunities. Recognizing that the Big Two reflect masculinity and femininity does not confine people to act in accordance with their gender but rather allows for novel interventions to reduce gender-based inequities.

Sex-specific academic ability and attitude patterns in students across developed countries

Article

Jul 2020
INTELLIGENCE

The extent of sex differences in psychological traits is vigorously debated. We show that the overall sex difference in the pattern of adolescents' achievement and academic attitudes is relatively large and similar across countries. We used a binomial regression modeling approach to predict the sex of 15 and 16 year olds based on sets of academic ability and attitude variables in three cycles of the Programme for International Student Assessment (PISA) data (N = 969,673 across 55 to 71 countries and regions). We found that the sex of students in any country can be reliably predicted based on regression models created from the data of all other countries, indicating a common (universal) sex-specific component. Averaged over three different PISA cycles (2009, 2012, 2015), the sex of 69% of students can be correctly classified using this approach, corresponding to a large effect. Moreover, the universal component of these sex differences is stronger in countries with relative income equality and women's participation in the labor force and politics. We conclude that patterns in academic sex differences are larger than hitherto thought and appear to become stronger when societies have more socioeconomic equality. We explore reasons why this may be the case and possible implications.

Expanding the evolutionary explanations for sex differences in the human skeleton

Article

May 2020

Holly M. Dunsworth

While the anatomy and physiology of human reproduction differ between the sexes, the effects of hormones on skeletal growth do not. Human bone growth depends on estrogen. Greater estrogen produced by ovaries causes bones in female bodies to fuse before males' resulting in sex differences in adult height and mass. Female pelves expand more than males' due to estrogen and relaxin produced and employed by the tissues of the pelvic region and potentially also due to greater internal space occupied by female gonads and genitals. Evolutionary explanations for skeletal sex differences (aka sexual dimorphism) that focus too narrowly on big competitive men and broad birthing women must account for the adaptive biology of skeletal growth and its dependence on the developmental physiology of reproduction. In this case, dichotomizing evolution into proximate‐ultimate categories may be impeding the progress of human evolutionary science, as well as enabling the popular misunderstanding and abuse of it.

Ideological Bias in the Psychology of Sex and Gender

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