Archives of Sexual Behavior

, Volume 36, Issue 2, pp 209–222

The Relation Between Sex Drive and Sexual Attraction to Men and Women: A Cross-National Study of Heterosexual, Bisexual, and Homosexual Men and Women

Authors

    • Department of PsychologyCalifornia State University
Original Paper

DOI: 10.1007/s10508-006-9146-z

Cite this article as:
Lippa, R.A. Arch Sex Behav (2007) 36: 209. doi:10.1007/s10508-006-9146-z

Abstract

Recent research suggests that, for most women, high sex drive is associated with increased sexual attraction to both women and men. For men, however, high sex drive is associated with increased attraction to one sex or the other, but not to both, depending on men's sexual orientation (Lippa, R. A., 2006, Psychological Science, 17, 46–52). These findings were replicated in a very large BBC data set and were found to hold true in different nations, world regions, and age groups. Consistent with previous research, lesbians differed from other women in showing the male-typical pattern, that high sex drive is associated with attraction to one sex but not the other. Bisexual women and men were more similar to same-sex heterosexuals than to same-sex homosexuals in their pattern of results. The correlation between same-sex and other-sex attraction was consistently negative for men, was near zero for heterosexual and bisexual women, and negative for lesbians. Thus, same-sex and other-sex attractions were, in general, more bipolar and mutually exclusive for men than for women. The current findings add to evidence that sexual orientation is organized differently in women and men and suggest a biological component to this difference.

Keywords

Sexual orientationSex driveHeterosexualityBisexualityHomosexualityCross-cultural research

Introduction

How are variations in sex drive related to individuals’ attractions to men and to women? According to classic learning theories of the mid-20th century, higher levels of drive increase the probability of dominant or well-learned behaviors, but decrease the probability of nondominant or poorly-learned behaviors (Hull, 1943; Spence, 1956; Zajonc, 1965). Applied to the domain of human sexuality, these theories predict that higher levels of sex drive will be associated with increases in individuals’ dominant kinds of sexual attractions and behaviors, but they will be unassociated or even negatively associated with individuals’ nondominant kinds of sexual attractions and behaviors. Thus, high-sex-drive heterosexual men and women should show increased attraction to other-sex but not to same-sex individuals, whereas high-sex-drive homosexual men and women should show increased attraction to same-sex but not to other-sex individuals.

In several previous studies that tested this hypothesis, I analyzed self-report measures of sex drive, attraction to men, and attraction to women in over 3,000 participants, and I examined correlations between sex drive and same- and other-sex attractions in heterosexual men, heterosexual women, gay men, and lesbian women (Lippa, 2006). Men showed the pattern predicted by classic drive theories—high sex drive was associated with increased sexual attraction to only one sex or the other, depending on men's sexual orientation. For most women, however, high sex drive was associated with increased sexual attraction to both men and women. Unlike the majority of women, however, lesbians showed a tendency to the male-typical pattern, i.e., high-sex-drive lesbians showed increased sexual attraction to women but not to men. The results also indicated that same-sex and other-sex attractions were more polarized (i.e., more “either-or” and mutually exclusive) for men than women. For example, the absolute difference between same-sex attraction and other-sex attraction was much larger, on average, for men than for women.

The greater male than female polarization of same- and other-sex attractions suggests that sexual orientation is organized differently in the two sexes. Several other kinds of evidence are consistent with this conclusion. Men report more mutually exclusive same-sex and other-sex attractions than women do, whereas women report more bisexual patterns of attraction than men do (Pattatucci, 1998). The distribution of men's same-sex-versus-other-sex attraction takes of the form of a “J-curve” more than the corresponding distribution for women does, indicating that men more than women are to be found at the extreme ends of the distribution (Wilson & Rahman, 2005). Same-sex attraction tends to be more negatively correlated with other-sex attraction in men than in women (Lippa, 2000; Lippa & Arad, 1997), and over the course of their lives, women tend to be more flexible and variable than men are in their attractions to men and to women (Baumeister, 2000; Diamond, 2000, 2003). Recent psychophysiological research shows that heterosexual men show genital arousal primarily to female sexual stimuli and homosexual men primarily to male sexual stimuli, whereas heterosexual and homosexual women show genital arousal to both male and female sexual stimuli (Chivers, Rieger, Latty, & Bailey, 2004) and even to films of sexual behaviors in nonhuman primates, again in contrast to men (Chivers & Bailey, 2005). Thus, in terms of physiological indicators of sexual arousal, men seem to have a more clearly defined sexual orientation than women do.

The different organization of sexual orientation in men and women may help explain why sex drive correlates with same-sex and other-sex attractions differently in the two sexes. In men, attractions to one sex tend to be highly dominant, whereas attractions to the other sex tend to be highly nondominant. In women, however, attractions to men and women are not as strongly segregated into dominant and nondominant responses. Thus, men show the pattern predicted by classic drive theories–higher sex drive tends to energize highly dominant responses (attractions to their preferred sex) but not highly nondominant responses (attractions to their non-preferred sex). For women, however, high sex drive may energize both same- and other-sex attractions, which are both present to some degree in many women.

Differences in the organization of men's and women’ same- and other-sex attractions may result, in part, from sex differences in the physiological processes of masculinization and feminization that underlie sexual orientation. In the earliest stages of development, the fetal brain appears to hold the potential to develop both male-typical and female-typical patterns of attraction. However, the hormonal processes that lead to male-typical development—in particular, the action of androgens—may produce masculinization and defeminization of neural structures related to sexual attractions. Such theorizing is consistent, at least in a heuristic sense, with physiological evidence showing that at the earliest stages of prenatal development, the internal reproductive organs of the human fetus have the potential to develop in either female or male directions. The female phenotype seems to be the default, however, which develops in the absence of hormonally mediated changes, whereas the male phenotype is a departure from the default, which results from hormonally initiated processes that produce both masculinization and defeminization of initially “bisexual” internal structures (for a recent review, see Hines, 2004).

Social-environmental theories may also help explain why men's and women's sexual orientations are patterned differently. The “either-or” nature of men's attractions may result, in part, from gender socialization that is more rigid for boys than for girls and from the fact that society punishes more strongly feminine behaviors in boys and men than it does masculine behaviors in girls and women (Fagot & Hagan, 1991; Jacklin, DiPietro, & Maccoby, 1984; Lippa, 2005). Such socialization pressures could lead heterosexual men more than heterosexual women to suppress other-sex attractions, although it is not clear what effect they would have on gay men's same-sex and other-sex attractions. Also, cultures may vary in the degree to which they construe male and female roles and same- and other-sex attractions as constituting mutually exclusive dichotomies (Lippa & Tan, 2001). Such cultural variations might influence the polarization of same- and other-sex attractions and the relation between sex drive and these attractions.

Traditionally, one way to test whether biological or cultural and social-environmental factors cause sex differences is to assess whether sex differences show cross-cultural consistencies or inconsistencies (see Lippa, 2005). In the current research, I investigated whether the sex differences found in my previous research—that sexual orientation is more polarized in men than women and that high sex drive is associated in women with increased attraction to both sexes but in men with increased attraction to only one sex or the other—are cross-culturally consistent. Strong cross-cultural consistency would support the hypothesis that biological factors contribute to these sex differences, whereas strong cross-cultural variation would support the hypothesis that they are socially and culturally determined.

One limitation of my previous findings was they were based on restricted samples. Most of my participants lived in southern California and were relatively young, most heterosexual participants were college students, and most gay and lesbian participants were recruited from gay and lesbian organizations. A second limitation of my previous studies was that they assessed relatively small samples of gay men and lesbians (159 and 103, respectively). In the current research, I analyzed data from the BBC Internet survey that assessed a very large, diverse, and international sample of participants. Because of the size of the BBC sample (over 200,000 participants), I could analyze data from 37 times as many gay men and 25 times as many lesbian women as I had previously, and I could analyze data from 86 times as many heterosexual men and 41 times as many heterosexual women as I had previously. The BBC data also allowed me to analyze data from large samples of bisexual men and women, groups that were not included in my previous studies. Finally, the size and diversity of the BBC sample allowed me to investigate the bipolarity of sexual orientation and the consistency of associations between sex drive and same- and other-attractions across nations, world regions, and age groups.

Method

Participants and procedure

From February through May 2005, the British Broadcasting Corporation (BBC) conducted an Internet survey, with the goal of presenting results in the BBC television documentary, “Secrets of the Sexes.” The BBC survey was designed in consultation with several researchers, including myself. Its main topic was human sex differences in cognition, motivation, personality, mating psychology, and sexuality. The survey was advertised on the BBC website and participants responded online. Because of the broad reach of the BBC as an international news source, survey participants came from all over the world. Those who logged on to the BBC survey website could complete a variety of psychological tests and questionnaires, which were arranged in six modules, each of which took about 5 min to complete. Most participants reported their sex and sexual orientation and also completed a two-item scale that assessed sex drive and single items that assessed their degree of sexual attraction to men and their degree of sexual attraction to women.

A total of 462,859 people worldwide responded in part or in full to the survey, with 255,114 responding to at least some items in every module. After being screened for age and inconsistent responding to sexual orientation items (a process described in the following section), the remaining sample included 102,961 heterosexual men (91% of men), 5,938 gay men (5%), 4,850 bisexual men (4%), 82,819 heterosexual women (90% of women), 2,548 lesbian women (3%), and 6,596 bisexual women (7%). The mean ages in years of the six groups were as follows: 32.2 (SD = 11.3) for heterosexual men, 31.9 (SD = 10.2) for gay men, 32.7 (SD = 11.8) for bisexual men, 31.1 (SD = 10.8) for heterosexual women, 33.1 (SD = 10.9) for lesbian women, and 28.3 (SD = 9.44) for bisexual women. Although the mean ages of various groups were similar, bisexual women stood out as being slightly younger than other groups. For additional information about the BBC sample and methodology, see Lippa (2007) and Reimers (2007).

Measures

Sex and sexual orientation

Participants reported their “gender” via a drop-down menu that asked them to select one of two responses: “male” or “female.” Sexual orientation was assessed via three items. A drop-down menu asked, “What is your sexual orientation?” and provided three response options: “Heterosexual (straight),” “Homosexual (gay/lesbian),” and “Bisexual.” In addition, two items asked “How sexually attracted are you to men” and “How sexually attracted are you to women,” with each question followed by seven radio buttons that allowed participants to respond on a seven-point scale that ranged from “not at all” to “very.” About 19% of the 255,114 participants who responded to at least some items in all survey modules did not respond to all three sexual orientation questions, leaving 209,275 participants with complete sexual orientation data.

Some participants showed inconsistency in their responses to the three sexual orientation items. To exclude these participants from further analysis, the following screening system was used. To be classified as “heterosexual,” a man had to describe himself as “Heterosexual (straight)” on the first item and he also had to report more attraction to women than to men on the other two items. To be classified as “homosexual,” a man had to describe himself as “homosexual (gay)” on the first item and he also had to report more attraction to men than to women on the other two items. To be classified as “bisexual,” a man had to describe himself as “bisexual” on the first item and he also had to report at least some attraction (i.e., more than “not at all”) to both men and to women. The same rules were applied, with appropriate changes, to women. The 3,457 participants who responded inconsistently to the sexual orientation items were excluded from further analyses, leaving 205,818 who were classified unambiguously as heterosexual, homosexual, or bisexual. The results reported in this article were not substantially altered when participants who responded inconsistently to the sexual orientation questions were included in analyses (labeled according to their drop-down menu responses).

Included in the demographic information collected from participants was age in years, which participants typed in as a string variable. Reported ages ranged from 0 to 99 years. To eliminate participants with suspiciously low or high ages and to eliminate participants who might be too young to be fully aware of their sexual orientation, I excluded from analysis participants who reported ages less than 18 and greater than 80 years. This left for analyses involving sexual orientation 113,749 men and 91,963 women.

Sex drive

Recent scales that assess sex drive typically ask respondents about their desire for sex, their frequency of sexual activity, their degree of thinking about and fantasizing about sex, and their evaluation of the rewardingness of sex (Lippa, 2006; Ostovich & Sabini, 2004; Spector, Carey, & Steinberg, 1996). For example, in my recent study of the relation between sex drive and same-sex and other-sex attractions (Lippa, 2006), I used a five-item sex drive scale that asked participants to rate how much they agreed with the following statements: “I have a strong sex drive.” “I frequently think about sex.” “It doesn't take much to get me sexually excited.” “I think about sex almost every day.” “Sexual pleasure is the most intense pleasure a person can have.”

The BBC survey included a 2-item sex drive scale that consisted of the first and third items just listed. Analysis of data from approximately 1800 individuals assessed by Lippa (2006; see Study 3), showed that this 2-item scale correlated .67 with a scale formed from the remaining 3 items of the original 5-item scale and .63 with Spector et al.'s (1996) Dyadic Sexual Desire scale. Thus, the 2-item scale showed reasonably good agreement with other self-report measures of sex drive. In the BBC survey, participants used radio buttons to respond to the two sex drive items on a seven-point scale that ranged from “disagree” to “agree.” The reliabilities (alpha) of the sex drive scale for all participants, men, and women were .79, .73, and .81, respectively.

Results

Sample demographics

Demographic information collected by the BBC Internet survey included relationship status, country of residence, ethnicity, education level, and income level. The breakdown of participants (i.e., those screened for age and consistency of sexual orientation responses) by their reported relationship status was as follows: 29% married, 29% single, 16% living together in a serious relationship, 15% living apart in a serious relationship, 8% in a casual relationship, 3% divorced, and under 1% widowed. Not surprisingly, these statistics varied somewhat for men and women and across sexual orientation groups. For example, 32% of heterosexual men, 29% of heterosexual women, 3% of gay men, 7% of lesbian women, 25% of bisexual men, and 19% of bisexual women reported being married. When the two “serious relationship” categories were collapsed, 26% of heterosexual men, 35% of heterosexual women, 39% of gay men, 53% of lesbians, 21% of bisexual men, and 39% of bisexual women reported being in a serious relationship.

Participants came from countries across the world, but the largest contingents came from the United Kingdom (45%), the United States (29%), Canada (5%), and Australia (4%). In aggregate, participants from continental Western Europe made up about 6% of the screened sample. Of those participants who responded to a question about ethnicity, most (85%) reported being White. The next largest categories were “Asian/Asian British” (6%), “mixed ethnic” (4%), “Chinese” (2%), and “Middle/Near Eastern” (1%). One survey question asked participants to report their highest level of schooling. In response to this item, 16% of participants reported having a post-graduate or professional degree, 41% reported university training, 13% reported “other college” training,” 11% reported vocational or technical college training, 18% reported secondary or high school education, and 1% reported primary or grammar school education.

Participants were asked to report their income level in terms of four categories: (1) 0 to 10,000 £ British (approximately 0 to $17,000 U.S.), (2) 10,000 to 25,000 £ British (approximately $17,000 to $43,500 U.S.), (3) 25,000 to 50,000 £ British (approximately $43,500 to $87,000 U.S.), and (4) greater than 50,000 £ British (greater than $87,000 U.S.). The percent of participants in each of these four income categories were respectively, 31, 32, 28, and 9%. Overall, the BBC survey participants could be characterized as relatively young, well educated, mostly White and Anglo-American, and relatively affluent. At the same time, participants showed substantial variation in age, education level, and income, and participants from non-Western nations (e.g., Japan, Malaysia) were mostly non-White. Because participants responded to the BBC survey online, it is likely that most were computer literate, and because the BBC survey was written in English, it is likely that participants from non-English-speaking countries were reasonably fluent in English.
https://static-content.springer.com/image/art%3A10.1007%2Fs10508-006-9146-z/MediaObjects/10508_2006_9146_Fig1_HTML.gif
Fig. 1

Male and female distributions of other-sex attraction (top panel) and same-sex attraction (bottom panel). The seven-point rating scales of attraction ranged from “not at all” to “very” attracted.

Selecting 12 nations and world regions

To assess the cross-national and cross-cultural consistency of findings, I conducted analyses separately for participants from 12 nations and world regions, as well for the sample as a whole (see Table 2). These nations and regions were selected because they yielded sample sizes that were large enough to allow, in general, meaningful analysis of heterosexual, bisexual, and homosexual participants. The 12 nations and world regions, listed in order of their total samples sizes were: the United Kingdom, the United States, Western Europe, Canada, Australia and New Zealand, Ireland, India, Eastern Europe, Singapore, Latin America, Malaysia, and Japan. Data for Western Europe comprised aggregated data from the following countries: Austria, Belgium, Denmark, Finland, France, Germany, Italy, the Netherlands, Norway, Spain, Sweden, and Switzerland. Data for Eastern Europe comprised aggregated data from the following countries: Bulgaria, Croatia, the Czech Republic, Estonia, Hungary, Lithuania, Romania, the Russian Federation, and Slovenia. Data for Latin American comprised aggregated data from the following countries: Argentina, Bolivia, Brazil, Colombia, Ecuador, Guatemala, Mexico, Uruguay, and Venezuela.

Distributions of other-sex and same-sex attraction for men and women

Figure 1 presents graphs that show the percent of men and women who reported each of seven self-reported degrees of other-sex attraction (top panel) and same-sex attraction (bottom panel). Other-sex attraction was defined as men's attraction to women and women's attraction to men, whereas same-sex attraction was defined as men's attraction to men and women's attraction to women. Men's and women's distributions differed significantly, both for other-sex attraction, χ2(6) = 3946.77, p < .001, and for same-sex attraction, χ2(6) = 16978.43, p < .001. Despite their significant difference, men's and women's distributions for other-sex attraction were not radically different. Men more often than women expressed the maximum degree of attraction to the other sex (a “7” rating on the seven-point scale of attraction). As ratings of other-sex attraction decreased from this maximum level, there were steep declines in the numbers of men and women who responded with successively lower ratings. However, the decline was steeper for men than women. Men's distribution of other-sex attraction showed more of a tendency to a “J-curve” than women's distribution did.

The more striking difference in male and female distributions occurred for same-sex attraction (bottom panel of Fig. 1). Considerably fewer women (39%) than men (63%) expressed the lowest degree of same-sex attraction, and the number of women expressing successively higher levels of same-sex attraction fell off much more gradually than the corresponding numbers of men. Once again, men showed more evidence of a “J-curve” than women did, with very large numbers of men reporting very low levels of same-sex attraction (“1” and “2” on a seven-point scale) and more men reporting the highest degree of same-sex attraction (“7”) than reporting each of the intermediate levels of “6,” “5,” “4,” or “3.”

Finally, Fig. 1 shows that although distributions of same-sex and other-sex attractions were quite skewed, there was nonetheless considerable variation in same-sex and other-sex attraction.

Sex and sexual orientation differences in sex drive

Mean sex drive levels were 5.47 (SD=1.27) for heterosexual men, 5.28 (SD=1.47) for bisexual men, 5.26 for gay men (SD=1.40), 4.51 (SD=1.59) for heterosexual women, 4.91 (SD=1.64) for bisexual women, and 4.60 (SD=1.67) for lesbian women. A two-way (sex by sexual orientation) ANOVA on sex drive yielded significant main effects for sex, F(1, 200313)=2019.58, p<.001, partial eta squared=.01, and sexual orientation, F(2, 200313)=34.55, p<.001, partial eta squared=.0003, and a significant interaction between sex and sexual orientation, F(2, 200313)=247.95, p<.001, partial eta squared=.002. The main effect for sex reflected the fact that men, on average, reported higher levels of sex drive than women did (d=.63), a finding consistent with the results of many other studies (Baumeister, Catanese, & Vohs, 2001). The main effect for sexual orientation was trivially small, though significant. The interaction between sex and sexual orientation reflected the fact that gay and bisexual men were somewhat lower in sex drive than heterosexual men were, whereas bisexual women were higher in sex drive than heterosexual and lesbian women were. All pair-wise comparisons of group means via t-tests showed significant differences, except for the comparison between bisexual and gay men.

Sex and sexual orientation differences in attraction to men and attraction to women

Table 1 presents the means and SDs of the variables “attraction to men” and “attraction to women” for heterosexual, bisexual, and homosexual men and women. Means showed expected patterns, although it is worth noting that in the BBC data both bisexual men and women reported, on average, higher levels of other-sex than same-sex attraction. A two-way (sex by sexual orientation) ANOVA on attraction to men yielded significant main effects for sex, F(1, 205706)=3727.49, p<.001, partial eta squared=.02, and sexual orientation, F(2, 205706)=11599.89, p<.001, partial eta squared=.10, and a significant interaction, F(2, 205706)=159483.46, p<.001, partial eta squared=.61. Similarly, a two-way (sex by sexual orientation) ANOVA on attraction to women yielded significant main effects for sex, F(1, 205706)=361.96, p<.001, partial eta squared=.002, and sexual orientation, F(2, 205706)=7758.91, p<.001, partial eta squared=.07, and a significant interaction, F(2, 205706)=115,711.26, p<.001, partial eta squared=.53. The powerful interaction effect reflects the strong but opposite effect of sexual orientation for the two sexes; for example, heterosexual men were much more attracted to women than gay men were, whereas heterosexual women were much less attracted to women than lesbians were.
Table 1

Means and SDs of attraction to men and attraction to women for heterosexual, bisexual, and homosexual men and women in the BBC data

 

Heterosexual

Bisexual

Homosexual

Attraction to Mena

 Men

1.39 (.72)

4.53 (1.56)

6.82 (.47)

 Women

6.55 (.79)

5.72 (1.41)

1.97 (.97)

Attraction to Womenb

 Men

6.74 (.61)

5.76 (1.37)

1.84 (1.00)

 Women

1.97 (1.15)

5.17 (1.27)

6.65 (.66)

aAbsolute range, 1–7.

bAbsolute range, 1–7.

To provide an overall sense of sex differences in attraction to men and attraction to women, I compared all men and all women on these variables using t-tests. Not surprisingly, there was a very strong sex difference in attraction to men, t(213448)=−708.26, p<.001, d=−3.08, and in attraction to women, t(212080) = 620.17, p < .001, d = 2.71. When these comparisons were restricted to just heterosexual men and women, there were even stronger sex differences in attraction to men, t(185778) =−1469.76, p<.001, d=−6.86, and in attraction to women, t(185778)=1146.24, p<.001, d=5.35. It is interesting to note the sex differences in attraction to men were larger than sex differences in attraction to women.

Table 1 also shows that within-group variability (i.e., SDs) in attraction to men and attraction to women differed across groups. In particular, bisexual men and bisexual women showed substantially greater variation in their attractions to men and to women than other groups of men and women did. This is perhaps to be expected, given that, by definition, bisexual individuals report having some degree of attraction to both sexes, whereas heterosexual and homosexual individuals report mostly having high attraction to one sex, and low attraction to the other. All pair-wise tests for differences between SDs in the six groups, for a given variable, yielded significant differences at p < .001, using Levene's test for equality of variances.

The association between sex drive and attraction to men and to women

Heterosexual men and women

Table 2 presents correlations between sex drive and attractions to men and to women, separately for heterosexual men and women. These correlations are presented for 12 non-overlapping nations and world regions and for younger (age ≥18 and ≤30 years), older (age >30 and ≤80 years), and all participants. Because ratings of sexual attraction to men and to women tended to be quite skewed, nonparametric correlations (Spearman's ρ) are presented rather than Pearson product-moment correlations. In cases where both kinds of correlation could be computed, their values proved to be quite similar. In a small number of analyses (e.g., when computing correlations for all men and for all women), Pearson's r is reported rather than ρ because sample sizes were too large to allow the computation of ρ by SPSS14.0 for Windows.
Table 2

Correlations (Spearman's ρ) of sex drive with sexual attraction to men and sexual attraction to women for heterosexual men and women

 

Heterosexual men

Heterosexual women

Nations/Regions

ρ: sex drive with attraction to men

ρ: sex drive with attraction to women

  N

ρ: sex drive with attraction to men

ρ: sex drive with attraction to women

N

United Kingdom

−.04***

.32***

 46,046

.33***

.14***

35,509

United States

−.07***

.31***

 26,908

.32***

.13***

23,987

Western Europe

−.02

.32***

  6,175

.33***

.12***

 3,919

Canada

−.05***

.32***

  5,241

.32***

.14***

 4,680

Australia, New Zeal

−.07***

.33***

  4,501

.32***

.15***

 3,931

Ireland

−.09***

.26***

  2,375

.26***

.06**

 2,191

India

−.06**

.34***

  1,977

.32***

.11*

 461

Eastern Europe

−.05

.31***

  919

.30***

.00

 789

Singapore

−.01

.26***

  689

.27***

.09*

 707

Latin America

−.05

.27***

  628

.32***

.05

 381

Malaysia

−.06

.26***

  347

.26***

.07

 249

Japan

−.09*

.39***

  257

.34***

.17

 132

Age ranges

      

 Age ≥18 and ≤30

−.07***

.30***

 50,511

.27***

.12***

43,758

 Age >30 and ≤80

−.04***

.33***

 50,012

.35***

.12***

36,335

 Age ≥18 and ≤80

−.04***,a

.32***,a

100,523

.32***

.13***

80,093

aPearson product-moment correlations, which were computed when there were too many cases for SPSS to compute Spearman's ρ.

*p<.05.

**p<.01.

***p<.001.

The pattern of correlations in Table 2 clearly replicated previous findings. For all heterosexual men, sex drive correlated positively with attraction to women, r(100521)=.32, p<.001, but negatively with attraction to men r(100521)=−.04, p<.001, whereas for all heterosexual women, sex drive correlated positively with both attraction to women, r(80091)=.14, p<.001, and attraction to men, r(80091)=.34, p<.001 (note, in Table 2, correlations for women are presented as ρ rather than r). The sex difference in correlations between sex drive and same-sex attraction was significant (−.04 versus .13, z=−36.05, p<.001), whereas the sex difference in correlations between sex drive and other-sex attraction was not (.32 versus .32). The corresponding comparisons for younger heterosexual men and heterosexual women and for older heterosexual men and heterosexual women yielded similar results.

Sex differences in correlations between sex drive and same-sex attraction were significant in nine of twelve nations/regions, and these differences were similar in pattern to the difference found for heterosexual men and women in general. Not surprisingly, the three countries and regions that did not yield significant differences (Eastern Europe, Latin America, and Malaysia) were among those with the smallest sample sizes. Despite these three non-significant differences, the pattern of correlations for heterosexual men and women was extremely consistent across nations and regions. In all cases, men's sex drive correlated negatively and women's sex drive correlated positively with their same-sex attractions. A binomial sign test (where the dichotomous comparison was whether men's and women's corresponding correlations were predominantly negative or positive over the 12 countries or regions) was significant at p = .0002. Comparing the corresponding correlations for heterosexual men and women across 12 nations and regions (i.e., comparing correlations in columns 1 and 5 of Table 2) using a paired-data t-test also showed a significant difference between men's and women's correlations, t(11)=−12.26, p<.001, with the mean correlation between sex drive and same-sex attraction for men=−.05 and for women=.11.

Homosexual men and women

Table 3 presents correlations between sex drive and same-sex and other-sex attractions for homosexual men and women. Correlations are not presented in Table 3 when sample sizes were less than 40 because these correlations were deemed likely to be unreliable. Once again, correlations are presented for 12 non-overlapping nations and world regions and for younger, older, and all participants. Unlike the corresponding correlations for heterosexual men and women, those for gay men and lesbians showed a similar pattern. Correlations between sex drive and same-sex attraction were significant, ρ(5814)=.22, p<.001 for all gay men, and ρ(2512)=.26, p<.001 for all lesbian women, whereas the correlations between sex drive and other-sex attraction were close to zero and non-significant, ρ(5874)=.00 for all gay men, and ρ(2512)=.01 for all lesbian women.
Table 3

Correlations (Spearman's ρ) of sex drive with sexual attraction to men and women for homosexual men and women

 

Homosexual men

Homosexual women

Nations/Regions

ρ: sex drive with attraction to men

ρ: sex drive with attraction to women

N

ρ: sex drive with attraction to men

ρ: sex drive with attraction to women

N

United Kingdom

.22***

−.02

2,797

−.03

.25***

 956

United States

.20***

.02

1,747

.04

.28***

1,014

Western Europe

.20***

−.04

 373

−.12

.20*

 130

Canada

.15*

.05

 267

.04

.26**

 139

Australia, New Zeal

.19**

.00

 248

.13

.15

 125

Ireland

.31**

−.06

 116

  32

India

  14

   3

Eastern Europe

  27

  10

Singapore

  32

  24

Latin America

.30*

−.04

  44

  14

Malaysia

  18

   7

Japan

  15

   0

Age ranges

      

 Age ≥18 and ≤30

.23***

−.01

2,795

−.04

.28***

1,117

 Age >30 and ≤80

.21***

.00

3,081

.04

.24***

1,397

 Age ≥18 and ≤80

.22***

.00

5,876

.01

.26***

2,514

Note. Correlations were not presented for groups with sample sizes less than 40.

*p<.05.

**p<.01.

***p<.001.

Furthermore, this pattern was consistent across the nations and regions that had sample sizes large enough to yield reliable correlations, and it was also consistent across age groups. When correlations between sex drive and same-sex attraction were compared for gay men and lesbians over the five nations and regions that had large enough sample sizes (UK, USA, Western Europe, Canada, and Australian and New Zealand), the difference was not significant, t(4)=−1.34, mean correlation for gay men=.19 and mean correlation for lesbians=.23. Similarly, when correlations between sex drive and other-sex attraction were compared for gay men and lesbians over the same five nations and regions the difference was not significant, t(4)=−.29, mean correlation for gay men=.00 and mean correlation for lesbians=.01.

Bisexual men and women

Table 4 presents correlations between sex drive and same-sex and other-sex attractions for bisexual men and women. Again, correlations are not presented when sample sizes were less than 40, and correlations are presented for 12 non-overlapping nations and world regions and for younger, older, and all participants. The pattern of correlations for bisexual men and women was similar but not identical to the pattern for same-sex heterosexuals. For all bisexual men, sex drive correlated positively with attraction to women, ρ(4795)=.27, p<.001, and weakly but positively with attraction to men, ρ(4795)=.04, p<.05, whereas for all bisexual women, sex drive correlated positively and relatively strongly with both attraction to women, ρ(6514)=.16, p<.001, and attraction to men, ρ(6514)=.33, p<.001. The difference between bisexual men's and bisexual women's correlations between sex drive and same-sex attraction was significant (.04 versus .16, z=−6.38, p<.001), and unlike the corresponding comparison for heterosexual men and women, the difference between bisexual men's and women's correlations between sex drive and other-sex attraction was also significant (.27 versus .33, z=−3.47, p<.05). Correlations for younger and older bisexual men and women were quite similar to those for bisexual men and women in general.
Table 4

Correlations (Spearman's ρ) of sex drive with sexual attraction to men and women for bisexual men and women

 

Bisexual men

Bisexual women

Nations/Regions

ρ: sex drive with attraction to men

ρ: sex drive with attraction to women

N

ρ: sex drive with attraction to men

ρ: sex drive with attraction to women

N

United Kingdom

.00

.30***

1,909

.35***

.14***

2,235

United States

.03

.27***

1,546

.31***

.17***

2,655

Western Europe

.03

.29***

 374

.34***

.20***

 453

Canada

.12

.21**

 243

.34***

.14**

 407

Australia, New Zeal

.04

.21**

 217

.42***

.20***

 324

Ireland

.02

.26*

  59

.32*

.05

  47

India

.16

.17

  74

  12

Eastern Europe

.18

.30

  40

.08

.23

  62

Singapore

  37

.30*

.36**

  65

Latin America

  31

.24

.26

  43

Malaysia

  22

  22

Japan

   8

  15

Age ranges

      

 Age ≥18 and ≤30

.05**

.26***

2,350

.31***

.16***

4,289

 Age >30 and ≤80

.02

.28***

2,447

.35***

.17***

2,227

 Age ≥18 and ≤80

.04*

.27***

4,797

.33***

.16***

6,516

Note. Correlations are not presented for groups with sample sizes less than 40.

*p<.05.

**p<.01.

***p<.001.

Although the correlations between sex drive and same-sex attraction were small for both bisexual men and heterosexual men, these correlations nonetheless tended to be positive for bisexual men and negative for heterosexual men and. The difference between the correlation for all bisexual men and the corresponding correlation for all heterosexual men was significant (.04 versus −.04, z=5.41, p<.001). This difference was also consistent over the eight nations/regions that had sufficiently large samples to yield correlations for both groups, paired-data t(7)=5.18, p=.001, mean correlation for bisexual men=.07 and mean correlation for heterosexual men=−.06.

The correlation between sex drive and other-sex attraction for all bisexual men (.27), was smaller than the corresponding correlation for all heterosexual men (.32), z=−3.71, p<.001. This difference was also consistent over the eight nations/regions that had sufficiently large samples to yield correlations for both groups, paired-data t(7)=−2.95, p=.02, mean correlation for bisexual men=.25 and mean correlation for heterosexual men=.32.

As noted before, correlations between sex drive and same-sex attraction were higher, in general, for bisexual women than for bisexual men, and they also tended to be slightly higher than heterosexual women's (for all bisexual women r=.16 and for all heterosexual women r=.13, z=−2.38, p<.05). This difference was also consistent over the eight nations/regions that had sufficiently large samples to yield correlations for both groups, paired-data t(8)=−2.52, p<.05, mean correlation for bisexual women=.19 and mean correlation for heterosexual women=.11. The correlation between sex drive and other-sex attraction for bisexual women (.33) was very similar to the corresponding correlation for heterosexual women (.32), z=.87, ns. The two corresponding correlations were also very similar over the eight nations/regions that had sufficiently large samples to yield correlations for both groups, paired-data t(8)=−.30, ns, mean correlation for bisexual women=.30 and mean correlation for heterosexual women=.31.

Finally, the correlation between sex drive and same-sex attraction for bisexual women (.16 for all bisexual women) was lower than the corresponding correlation for lesbians (.26 for all lesbians), z=−4.46, p<.001. In contrast, the correlation between sex drive and other-sex attraction for bisexual women (.33 for all bisexual women) was higher than the corresponding correlation for lesbians (.01 for all lesbians), z=14.17, p<.001.

Correlations between attraction to men and attraction to women

In the introduction, I hypothesized that sex differences in the association between sex drive and same-sex attraction may result from the fact that same-sex and other-sex attractions are more polarized in men than in women. One way to test the hypothesis of greater male than female polarization is to test for a sex difference in the absolute value of the difference between attraction to men and attraction to women. Indeed, this measure of polarization was larger for men than for women, t(209872)=134.45, p<.001, male mean=5.15 and female mean=4.30, d=.59. Furthermore, sex drive correlated more strongly with this index of polarization for men, r(113275)=.19, p<.001, than for women, r(91039)=.05, p<.001, a difference that was significant, z=31.97, p<.001.

Table 5 presents additional data relevant to the hypothesis that men are more polarized in their attractions to men and women than women are—namely, correlations between sexual attraction to men and sexual attraction to women, computed separately for heterosexual men, bisexual men, gay men, heterosexual women, bisexual women, and lesbian women, and also computed for these groups in different countries, regions, and age categories. The pattern that was most apparent in Table 5 was the obvious sex difference. All correlations for men were negative, relatively large, and significant, whereas correlations for women were mixed in sign, relatively small, and often non-significant. Lesbians constituted the one group of women that showed consistently negative and often significant correlations.
Table 5

Correlations (Spearman's ρ) between sexual attraction to men and sexual attraction to women for heterosexual, bisexual, and homosexual men and women

 

Men

Women

Nations/Regions

Heterosexual

Bisexual

Homosexual

Heterosexual

Bisexual

Homosexual

United Kingdom

−.14***

−.36***

−.21***

.02***

−.01

−.20***

United States

−.15***

−.37***

−.16***

−.02*

−.03

−.16***

Western Europe

−.15***

−.26***

−.17**

.01

−.02

−.06

Canada

−.12***

−.33***

−.13*

.03*

.04

−.05

Australia, New Zeal

−.15***

−.47***

−.23***

.04**

−.07

−.15

Ireland

−.20***

−.56***

−.28**

−.08***

−.31*

India

−.10***

−.51***

.15**

Eastern Europe

−.20***

−.39*

−.07*

−.22

Singapore

−.22***

−.03

−.10

Latin America

−.27***

−.41**

−.09

−.05

−.05

Malaysia

−.32***

−.08

Japan

−.13*

.10

Age ranges

      

 Age ≥18 and ≤30

−.17***

−.37***

−.22***

−.04***

−.03*

−.15***

 Age >30 and ≤80

−.11***

−.34***

−.18***

.03***

−.02

−.17***

 Age ≥18 and ≤80

−.10***,a

−.36***

−.20***

.01**

−.03*

−.16***

aPearson product-moment correlations, which were computed when there were too many cases for SPSS to compute Spearman's ρ. Correlations are not presented for groups with sample sizes less than 40.

*p<.05.

**p<.01.

***p<.001.

The correlations presented in the bottom row of Table 5 were computed for all heterosexual men, bisexual men, gay men, heterosexual women, bisexual women, and lesbian women. All pair-wise tests of differences between these correlations were significant, even the comparison of the .01 correlation for heterosexual women and the −.03 correlation for bisexual women, z=3.11, p<.001. Thus, the six groups can be ordered as follows in terms of the degree of negative correlation between their attractions to men and their attractions to women: bisexual men, gay men, lesbian women, heterosexual men, bisexual women, and heterosexual women. The correlation for heterosexual men was computed as r, whereas all other correlations were computed as ρ, and this possibly affected the ranking of heterosexual men.

To some extent, the especially high negative correlation for bisexual men may reflect a statistical phenomenon. Because the three groups of men were defined in terms of men's sexual orientation, the variables “attraction to men” and “attraction to women” were necessarily restricted in range in each group. As Table 1 showed, this range restriction was relatively large for heterosexual and gay men and smaller for bisexual men (i.e., SDs were lower for heterosexual and gay men than for bisexual men). Thus, bisexual men's high variance on “attraction to men” and “attraction to women” could plausibly serve as an explanation for why bisexual men showed stronger negative correlations between these two variables than heterosexual or gay men did. It is interesting to note that bisexual women similarly showed higher variances on these variables than other women did, but unlike bisexual men, they did not show strong negative correlations between their same-sex and other-sex attractions. In fact, the strongest negative correlations among women occurred for lesbians. Apparently, even though bisexual women varied substantially in both their attractions to men and to women, these two dimensions of attraction were nonetheless largely independent for them.

Because of the restriction of range in “attraction to men” and “attraction to women” that occurred within sexual orientation groups, I also computed the correlation between these two variables for men in general and for women in general. The size of these samples required that I compute Pearson's r rather than Spearman's ρ. The correlation for all men, unselected for sexual orientation, was −.73 (N=115,892, p<.001), and the corresponding correlation for women was −.37 (N=93,982, p<.001). Not surprisingly, given the substantial difference between these two correlations and the very large sample sizes, the difference between these two correlations was highly significant, z=−123.08, p<.001.

The patterns of correlations in Table 4 were highly consistent across nations and regions. Mean correlations for the six sexual orientation groups, across nations and regions, were −.18 for heterosexual men, −.41 for bisexual men, −.23 for gay men, .00 for heterosexual women, −.08 for bisexual women, and −.11 for lesbian women. The order of these means from smallest to largest—bisexual men, gay men, heterosexual men, lesbian women, bisexual women, and heterosexual women—was the same as that for the correlations in the bottom row of Table 4, except for the reversed positions of heterosexual men and lesbians. Paired-data t-tests generally confirmed the reliability of this rank ordering, across nations and regions. Correlations for bisexual men were smaller than those for gay men, t(5)=−7.11, p=.001; correlations for gay men were smaller than those for heterosexual men, t(6)=−3.22, p=.02; correlations for lesbian women were smaller than those for bisexual women, t(5)=3.31, p=.02; and correlations for bisexual women tended to be smaller than those for heterosexual women, t(8)=−2.24, p=.06. The only comparison of adjacent groups in the rank ordering that was not significant was the comparison of correlations for heterosexual men and lesbian women, t(5)=−1.28, ns. Binomial sign tests, where the dichotomous comparison was whether a correlation was negative or not negative, indicated that correlations were consistently negative across nations/regions for heterosexual men (p<.001), bisexual men (p<.01), gay men (p<.01), bisexual women (p<.05), and lesbian women (p<.05), but not for heterosexual women (ns).

Finally, the patterns of correlations just described for heterosexual men, bisexual men, gay men, heterosexual women, bisexual women, and lesbian women tended to be consistent across age groups. There was a slight tendency for correlations to be more negative for younger as opposed to older participants, and this younger-versus-older difference was significant for heterosexual men (z=−9.70, p<.001) and for heterosexual women (z=−9.87, p<.001), due in part to the very large sample sizes.

Discussion

Virtually all of the main findings reported in Lippa (2006) replicated in the current analyses of the BBC data. Men proved to be more polarized in their same-sex and other-sex attractions than women were. This was apparent in the distributions of men's and women's other-sex and same-sex attractions presented in Fig. 1, it was apparent in the significant sex difference in the absolute difference between same- and other-sex attraction, and it was also apparent in the obvious sex differences in correlations between attraction to men and attraction to women presented in Table 4. Perhaps the single most dramatic demonstration of sex differences in the bipolarity of sexual orientation was provided by correlations between attraction to men and attraction to women for all men (r=−.73) and for all women (r=−.37). Expressed in terms of variance accounted for, other-sex attraction accounted for almost four times as much variance in same-sex attraction for men (r2=.53) as it did for women (r2=.14), and the difference between these two correlations was significant at p<10−15.

The current results also replicated my earlier demonstration of sex differences in associations between sex drive and same- and other-sex attractions. For most women, with the exception of lesbians, high sex drive was associated with increased attraction to both sexes. For all groups of men, in contrast, high sex drive was associated with increased attraction to one sex but with little change in attraction to the other sex. For heterosexual and gay men, sex drive was weakly but negatively correlated with attraction to their non-preferred sex, whereas for bisexual men sex drive was weakly but positively correlated with attraction to men, their less preferred sex.

Both of the main findings in the current report—the greater polarization of men's than women's sexual orientation and sex differences in associations between sex drive and same- and other-sex attractions—were highly consistent across nations, regions, and age groups, a finding that increases the likelihood that biological factors contribute to these differences. The strength and consistency of the current findings is doubly impressive given that attraction to men and attraction to women were assessed with one-item measures and sex drive was assessed with a two-item scale. Study 3 in Lippa (2006) showed that correlations and effect sizes were considerably larger when more reliable multi-item scales of sex drive, attraction to men, and attraction to women were used.

The current study extended previous research by presenting results for large numbers of bisexual men and women as well as for large numbers of heterosexual and homosexual men and women. The patterns of correlations between sex drive and same- and other-sex attractions for bisexual men and women tended to be similar to the patterns for same-sex heterosexuals. Bisexual men's sex drive tended to correlate more strongly with their attraction to women than with their attraction to men, whereas bisexual women's sex drive tended to correlate substantially with both their attraction to men and to women. At the same time, bisexual men showed a subtle but consistent difference from heterosexual men in that their sex drive correlated weakly but positively with same-sex attraction, whereas heterosexual men's sex drive correlated weakly but negatively with same-sex attraction.

There was a second noteworthy difference between bisexual men and other men. Negative correlations between same-sex and other-sex attraction were stronger for bisexual men than for heterosexual and homosexual men. The seeming greater bipolarity of bisexual men's same-sex and other-sex attractions might seem paradoxical at first glance, given that bisexual men, by definition, are not supposed to be as “either-or” in their attractions to men and women as heterosexual and gay men are. However, as noted earlier, the large negative correlations for bisexual men may reflect a statistical phenomenon. Bisexual men showed greater variation than heterosexual and gay men did in their attraction to men and attraction to women (see Table 1), and this greater variation may allow these two variables to correlate more strongly for bisexual men than for heterosexual and gay men, who have more restricted ranges of values.

It is important to note that differences in within-group variability in attraction to men and attraction to women cannot explain the patterns of correlations between sex drive and same- and other-sex attractions that were observed in various groups. For example, one plausible explanation for why heterosexual men's sex drive did not correlate with their same-sex attractions is that their same-sex attractions varied very little, and this restriction in range produced small correlations. However, note that bisexual men showed much the same pattern of sex drive correlations as heterosexual men did (i.e., their sex drive correlated very weakly with same-sex attractions and more strongly with other-sex attractions) despite the fact that bisexual men showed much higher variation in their same-sex attraction than heterosexual men's did. Furthermore, heterosexual men showed even less variation in their attractions to women (SD=.61) than in their attractions to men (SD=.72; see Table 1), yet their sex drive correlated substantially with their attractions to women.

My previous research hinted that lesbians showed more male-typical patterns of results than heterosexual and bisexual women did. The current results demonstrated this phenomenon more convincingly. Lesbians’ self-reported sex drive correlated strongly with their dominant attractions toward women, but weakly with their non-dominant attractions to men. Furthermore, lesbians’ same-sex and other-sex attractions showed male-typical negative correlations with one another. The current findings on lesbians were much more conclusive than my previous ones because the current sample of lesbians was so large and diverse compared to my previous samples. The pattern of results for lesbians shows that not only do lesbians differ from the majority of women in the “direction” of their attractions (i.e., they are attracted to women but not to men), but that they also differ in the “organization” (i.e., bipolarity) of their attractions.

Some of the results presented in Lippa (2006) hinted that lesbians may, on average, have higher levels of sex drive than heterosexual women do. If lesbians, in fact, have higher levels of sex drive than other women, then this might serve to explain their pattern of results. Perhaps the three groups of men, as well as lesbian women, showed male-typical patterns (i.e., greater polarization of sexual orientation and associations between sex drive and attraction to one sex but not the other) because all of these groups had, on average, higher sex drive levels. Although appealing, this hypothesis was not supported by the current data. As described in the results section, lesbians—the group of women who showed the male-typical pattern of results—were not the female group with the highest mean level of sex drive. Rather, bisexual women reported the highest mean levels of sex drive (see Schmitt, 2005, pp. 303–304, for related cross-cultural findings that bisexual women are also higher than heterosexual and lesbian women on sociosexuality). Despite their high sex drive, however, bisexual women tended to show a female-typical pattern of results, like heterosexual women, i.e., bisexual women's sex drive was substantially correlated with their attraction to both men and women, and the correlation between their same-sex and other-sex attraction was relatively weak.

The pattern of results for bisexual and lesbian women raises the intriguing possibility that the same-sex attractions experienced by each group may have somewhat different origins. Because bisexual women tend to be high-sex-drive women, their high sex drive may serve to energize their same-sex attractions—attractions that are latent in most women. In contrast, lesbian women may not be especially high on sex drive compared to other women, but they are women whose same-sex and other-sex attractions are organized differently from other women's, in the “either-or” fashion typical of men. In a sense, then, bisexual women might be characterized as “predominantly heterosexual women with high sex drives,” whereas lesbians might be characterized as women who are attracted to women but not to men.

The two kinds of sex differences documented here–greater male polarization of sexual orientation and sex differences in associations between sex drive and same- and other-sex attractions—were highly consistent across nations, world regions, and ages, and, as noted before, this consistency increases the likelihood that biological factors contribute to these sex differences. I speculated at the start that sex differences in the organization of same- and other-sex attractions might result from the prenatal action of hormones, particularly androgens, at critical stages of development. If this hypothesis is correct, then heterosexual men, bisexual men, gay men, and lesbian women are all exposed to some hormonal influence early in development that produces a more polarized, “either-or” sexual orientation, whereas heterosexual and bisexual women are not exposed or are not exposed as much to this influence.

In a sense, gay men constitute the most paradoxical group in relation to the neurohormonal theory just described, for gay men are “masculinized” in terms of the organization of their sexual orientation (i.e., they are “either-or” in sexual orientation, like all men) but they are “feminized” in the direction of their attractions (i.e., they are attracted to men but not to women). Four post hoc, speculative additions to the neurohormonal hypothesis may help explain these results for gay men: (1) There are different prenatal critical periods for establishing the “organization” versus “direction” of sexual orientation, and gay men are “masculinized” during one critical period but “feminized” during another. (2) Some factors that lead to male homosexuality (e.g., hyper-normal exposure to androgens at critical stages of development; see McFadden, 2002) might lead to a “masculine” organization of sexual orientation but to “feminine” sexual attractions. (3) The “organization” and “direction” of sexual orientation may have separate neural substrates, and some biological factors (e.g., androgens) may have locally variable effects, depending on other factors such as the distribution of androgen receptors in tissues. (4) All biological males, and perhaps some lesbians too, receive a sufficiently high prenatal dose of androgens to masculinize the organization of their sexual orientation, but there are other causal factors (e.g., immunological processes that affect male fetuses, as suggested by the fraternal birth order effect; see Blanchard, 2004) that sometimes lead to feminization of males’ sexual attractions.

Yet, a fifth possibility is that the “direction” of sexual attractions is channeled by the organizational effects of prenatal hormone exposure, whereas the “organization” of sexual orientation results more from the activational effects of adult hormone levels. One commonality among heterosexual, bisexual, and gay men is that they all experience dramatically increased testosterone levels during and after puberty. This might help explain why all men show a similar organization to their sexual orientation. For this hypothesis to be true, though, lesbians would need to share this activational effect with men, perhaps as a result of higher adult androgen levels. Empirical evidence that lesbians have higher adult androgen levels than other women is at best mixed (Meyer-Bahlburg, 1984; Peplau, Spalding, Conley, & Veniegas, 1999; Singh, Vidaurri, Zambarano, & Dabbs, 1999; Wilson & Rahman, 2005), although it could be the case that lesbians are, for some reason, more sensitive to the activational effects of androgens.

For now, all of the previous hypotheses are simply conjectures, and detailed theoretical explanations of the current findings are lacking. Nonetheless, the finding that the sex differences documented here are consistent across nations, world regions, cultures, and age groups suggests that adequate explanations of these differences may need to appeal to biological factors of some sort.

Copyright information

© Springer Science+Business Media, LLC 2007