Monday, June 27, 2011

Biology, men and women....a summary (shamelessly stolen)

I came across this from an egalitarian (?) blog:

If the scientific evidence comes in that proves systematic, cross-cultural differences between men and women-- not "95% overlapping bell curves," but "the vast majority of men are more X than the vast majority of women"-- then that would destroy my feminism. If the 95% overlapping bell curves apply not to a few traits but to every trait from the Big Five to cooking ability, then that would also destroy my feminism.

Because that means that the social pressure is not the result of arbitrary stereotypes and fear of the different: it's an attempt to mold people so they will actually be similar to most people of their gender, which would aid their social and romantic life. Because that means the lack of stay-at-home dads and female CEOs is not the result of sexism, but of nature.

And wondered, is there evidence? Well, let us see:

Time to steal from a recent Pelle Billing post (hehe):

It appears that while men and women have the same average IQ, the level of cognitive function is achieved in very different ways. Not only do women and men employ different brain regions, there is also a vast difference in the emphasis on gray and white matter.

[...]Functional brain imaging studies have reported a number of sex differences (Cahill et al., 2001; Gur et al., 2000; Haier and Benbow, 1995; Mansour et al., 1996; Neubauer et al., 2002; Shaywitz et al., 1995, 2001), but task-specific demands on cognitive resources with functional studies must always be considered as the task itself could affect interpretation of functional imaging results. Structural imaging correlated with off-line analyses of various cognitive performance measures and traits, on the other hand, can identify those differences in neuroanatomy which may underlie the cognitive measure of interest, irrespective of any task design constraints.

[...]With respect to voxel types, men had roughly 6.5 times the number of GM [gray matter] voxels identified as related to intellectual functioning as did women, and women had roughly nine times more WM [white matter] voxels than did men.

[...]The current results contribute to a growing body of evidence demonstrating that, although the sexes do not differ in general intellectual ability, the neural substrates of general intelligence are different. Whether similar neuroanatomical differences are associated with specific mental abilities (assessed for example by WAIS subtests) remains to be determined; our VIQ and PIQ findings need replication with larger samples.

There seem to be fundamental differences when it comes to brains. What else do we got? As Pelle has written a lot about biology I am going to borrow some more from this blog (seriously follow him, this is an excellent blog):

We have knowledge about girls and women who were exposed to abnormally high testosterone levels in utero (for various biological reasons, one of them being the medical condition CAH). These girls, who have been affected by testosterone as their fetal brains were developing, are more likely to be interested in a style of playing that is generally considered “boyish”.

Furthermore, from age 11 these girls are more likely to be interested in having a career (Dittman et al, 1990a) and less likely to want to have children or be a stay-at-home mom than other girls their age. This is something that happens even though the girl is raised as a girl, and expected to behave like a girl. As grown women, they are more likely to have a high status career (Purigoy and Koopmans, 1979; W Gallagher, 1998; Bancroft et al, 1983)

About brains and tweens:

a new functional magnetic resonance imaging (fMRI) study of children offers at least one explanation for some common tween social behaviors: girls are hardwired to care about one-on-one relationships with their BFFs (best friends forever), while the brains of boys are more attuned to group dynamics and competition with other boys.

[...]The results suggest that as girls progress from early puberty to late adolescence, certain regions of their brains become more active when they face a potential social interaction. Specifically, when an older girl anticipates meeting someone new — someone she believes will be interested in her — her nucleus accumbens (which is associated with reward and motivation), hypothalamus (associated with hormone secretion), hippocampus (associated with social learning) and insula (associated with subjective feelings) all become more active. By contrast, boys in the same situation show no such increase in activity in these areas. In fact, the activity in their insula actually declines.

[...]Perhaps it’s evidence that evolution has programmed boys to compete within large groups, so they can learn to eliminate rivals for women — and that girls have been programmed to judge, one-on-one, who would be the most protective father for offspring.

We continue with Testosterone:

Prior research has shown that testosterone enhances competitiveness and dominance, reduces fear, and is associated with risky behaviors like gambling and alcohol use. However, until now, the impact of testosterone on gender differences in financial risk-taking has not been explored.

The researchers, using an economic-based measure of risk aversion, found that higher levels of testosterone were associated with a greater appetite for risk in women, but not among men. However, in men and women with similar levels of testosterone, the gender difference in risk aversion disappeared. Additionally, the researchers reported that the link between risk aversion and testosterone predicted career choices after graduation: individuals who were high in testosterone and low in risk aversion chose riskier careers in finance.

Cross cultural personality traits:

Previous research suggested that sex differences in personality traits are larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with those of men. In this article, the authors report cross-cultural findings in which this unintuitive result was replicated across samples from 55 nations (N = 17,637). On responses to the Big Five Inventory, women reported higher levels of neuroticism, extraversion, agreeableness, and conscientiousness than did men across most nations. These findings converge with previous studies in which different Big Five measures and more limited samples of nations were used. Overall, higher levels of human development--including long and healthy life, equal access to knowledge and education, and economic wealth--were the main nation-level predictors of larger sex differences in personality. Changes in men's personality traits appeared to be the primary cause of sex difference variation across cultures. It is proposed that heightened levels of sexual dimorphism result from personality traits of men and women being less constrained and more able to naturally diverge in developed nations. In less fortunate social and economic conditions, innate personality differences between men and women may be attenuated.

In many studies, including several meta-analytic investigations, it has been found that men tend to be more assertive and risk taking than women, whereas women are generally higher than men in anxiety and tender-mindedness (Brody & Hall, 2000; Byrnes, Miller, & Schafer, 1999; Feingold, 1994; Kring & Gordon, 1998; Lynn & Martin, 1997; Maccoby & Jacklin, 1974). These sex differences in personality traits can be detected in early childhood (Else-Quest, Hyde, Goldsmith, & Van Hulle, 2006; Wilgenbusch & Merrell, 1999) and remain fairly constant across adulthood (Feingold, 1994; McCrae & Costa, 1984). The effects of these sex differences lead to predictable differences in men’s and women’s leisure behaviors, occupational preferences, and health-related outcomes (Browne, 1998; Collaer & Hines, 1995; Lippa, 2005).

Observed sex differences in personality traits such as assertiveness and anxiety also appear to be culturally pervasive (Costa, Terracciano, & McCrae, 2001; Lynn & Martin, 1997). Feingold (1994) found that women in Canada, China, Finland, Germany, Poland, and Russia tended to score higher than men on scales related to the personality traits of neuroticism, agreeableness, and conscientiousness. Men, in contrast, scored higher in the extraversion related trait of assertiveness across cultures. In a much larger study, self-report responses to the Revised NEO Personality Inventory (NEO-PI-R) across 36 cultures revealed that women in most countries are higher in several traits related to neuroticism, agreeableness, warmth, and openness to feelings, whereas men score higher on scales measuring assertiveness and openness to ideas (Costa et al., 2001; McCrae, 2002).

[...]Sex differences in most personality traits, however, are not uniform in magnitude across all samples. At times, sex differences can be much larger in some cultures than in others (Fischer & Manstead, 2000; Guimond et al., 2007; Schwartz & Rubel, 2005). One unexpected finding has been that sex differences in personality traits are often larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with men (Costa et al., 2001; McCrae, 2002). Both in self-report and in other-report data, Asian and African cultures generally show the smallest sex differences, whereas European and American cultures—in which living standard and gender equity indexes are generally higher—show the largest differences (McCrae et al., 2005). With improved national wealth and equality of the sexes, it seems differences between men and women in personality traits do not diminish. On the contrary, the differences become conspicuously larger.

This study provides strong support for the claim that with greater human development and with greater opportunities for gender equality, the personalities of men and women do not become more similar (see also Costa et al., 2001; McCrae, 2002; McCrae et al., 2005). To the contrary, in more prosperous and egalitarian societies the personality profiles of men and women become decidedly less similar. Moreover, these changes appear to result from men’s cross-cultural personality variation. In more traditional and less developed cultures a man is, indeed, more like a woman, at least in terms of self-reported personality traits.

Infant behavior:

Sexual dimorphism in sociability has been documented in humans. The present study
aimed to ascertain whether the sexual dimorphism is a result of biological or sociocultural differences between the two sexes. 102 human neonates, who by definition have
not yet been influenced by social and cultural factors, were tested to see if there was a
difference in looking time at a face (social object) and a mobile (physical-mechanical
object). Results showed that the male infants showed a stronger interest in the physicalmechanical mobile whilst the female infants showed a stronger interest in the face. The
results of this research clearly demonstrate that sex differences are in part biological in

[...]Sexual dimorphism in sociability has been documented in humans. The present study
aimed to ascertain whether the sexual dimorphism is a result of biological or sociocultural differences between the two sexes. 102 human neonates, who by definition have
not yet been influenced by social and cultural factors, were tested to see if there was a
difference in looking time at a face (social object) and a mobile (physical-mechanical
object). Results showed that the male infants showed a stronger interest in the physicalmechanical mobile whilst the female infants showed a stronger interest in the face. The
results of this research clearly demonstrate that sex differences are in part biological in

[...]In summary, we have demonstrated that at 1 day old, human neonates demonstrate sexual
dimorphism in both social and mechanical perception. Male infants show a stronger
interest in mechanical objects, whilst female infants show a stronger interest in the face.
The male preference cannot have simply been for a moving stimulus, and both stimuli
moved. Rather, their natural motion differed, the face with biological motion, the mobile
with physico-mechanical motion. Naturally, these results apply to males and females
averaged over a group, and not to all individuals. At such an age, these sex differences
cannot readily be attributed to postnatal experience, and are instead consistent with a
biological cause, most likely neurogenetic and/or neuroendocrine in nature.

More on infants:

Twelve-month-old infants (n=60) were presented with a video of cars moving, or a face moving, in a looking preference experimental design. This tested the prediction from our earlier work that attention in males is drawn more to mechanical motion, whilst attention in females is drawn more to biological motion. Results supported this prediction. These findings are discussed in relation to social and biological determinism.

Different toy preferences in infants which even monkeys share:

There could be a biological reason why boys love to play with toy trucks and girls prefer their dolls, British researchers say.

Dr. Brenda Todd and her student Sara Amalie O'Toole Thommessen from City University London studied 90 infants between the ages of nine months to 36 months and concluded children choose to play with gender-specific toys from the moment they can first crawl.

This study is the first to find such consistent and stable differences in toy choices between genders in children younger than 18 months.

[...]Evidence indicating that sex-linked toy preferences exist in two nonhuman primate species support the hypothesis that developmental sex differences such as those observed in children's object preferences are shaped in part by inborn factors. If so, then preferences for sex-linked toys may emerge in children before any self-awareness of gender identity and gender-congruent behavior. In order to test this hypothesis, interest in a doll and a toy truck was measured in 30 infants ranging in age from 3 to 8 months using eye-tracking technology that provides precise indicators of visual attention. Consistent with primary hypothesis, sex differences in visual interest in sex-linked toys were found, such that girls showed a visual preference (d > 1.0) for the doll over the toy truck and boys compared to girls showed a greater number of visual fixations on the truck (d = .78). Our findings suggest that the conceptual categories of "masculine" and "feminine" toys are preceded by sex differences in the preferences for perceptual features associated with such objects. The existence of these innate preferences for object features coupled with well-documented social influences may explain why toy preferences are one of the earliest known manifestations of sex-linked social behavior.

The way that transgendered persons report feeling after hormone therapy to cite from Wiki:

female to male:
Most trans men report an increase of energy and an increased sex drive. Many also report feeling more confident.

male to female:
decreased libido

As an example from an interview with Chaz Bono:

There is something in testosterone that makes talking and gossiping really grating. I’ve stopped talking as much. I’ve noticed that Jen can talk endlessly.” He shrugged. “I just kind of zone out.”

“You just don’t care!”

“I just don’t care!” He laughed. “I’ve learned that the differences between men and women are so biological. I think if people realized that, it would be easier. I would be a great relationship counselor. I know the difference that hormones really make.”

Sex, for him, is completely different now. “I am completely monogamous,” he said, “but I need release much more often than Jen does.”

I would say this is all I got. Now I am not saying we should enforce gender roles. Quite the contrary, everyone is different and we should make sure that everyone can freely decide how to live his/her life. It just means we might end up with more stay-at-home-mums and more male ceos by design. Oh and that the above mentioned feminism is no more...

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