Category: Gender Difference

Hormones shape our bodies, make us fertile, excite our most basic urges, and as scientists have known for years, they govern the behaviors that separate men from women. But how?

Now a team of scientists at the University of California, San Francisco (UCSF) has uncovered many genes influenced by the male and female sex hormones testosterone and estrogen that, in turn, govern several specific types of male and female behaviors in mice.

The UCSF team selectively turned many of these genes off one by one and found they could manipulate individual behaviors in the mice, like their sex drive, desire to pick fights, or willingness to spend extra time caring for their young.

"It's as if you can deconstruct a social behavior into genetic components," said Nirao Shah, MD, PhD, an associate professor in the Department of Anatomy at UCSF who led the research, which is published in the 2/3/12 issue of the journal Cell. "Each gene regulates a few components of a behavior without affecting other aspects of male and female behavior.

In addition to illuminating the role of genes in male and female behavior, Shah said, the results also have greater implications: If male and female behaviors can be broken down into individual component parts, what other complex behaviors could similarly be deconstructed?

Identifying how genetic differences in our brains account for the differences in our behavior may also be a starting point for understanding how to better address human mental illness and neurodegenerative conditions in which such gender differences exist. For example, autism is four times more common in males than in females.

"Some of the genes we have identified in our study have indeed been implicated in various human disorders that are found in sex-skewed ratios," said Shah. "We won't immediately find all the answers to these disorders based on this research alone, but in the future, it might indeed help to identify more informed ways of treating such conditions."

Hormones, Sex, and Society

Scientists have known for years that hormones exert a profound control over male and female biology. They influence whether an embryo develops into a male or female fetus. They kick in during puberty and promote gender-specific characteristics, such as facial hair in men and breasts in women. They also stimulate the production of male sperm and female ova.

These actions have led to the widespread use of hormones in mainstream and fringe medicine for years. A major part of sexual reassignment procedures involves the long-term administration of hormones like estrogen or testosterone. Athletes seeking a competitive edge and middle-aged men seeking to prolong the vigor of youth sometimes use testosterone — often inducing aggressive behavior in the process.

While the connection between sex hormones and behavior has been known for years, scientists have only recently made significant headway in demonstrating how profoundly one affects the other by altering the levels of male and female hormones in laboratory animals.

Female mice in the laboratory normally exhibit what one might consider classic motherly behaviors — mating with male mice and nurturing their young. But female mice with a genetic trait making them unable to sense the hormone estrogen lose their interest in sex and spend less time caring for their offspring.

Fortified by testosterone, male mice in the laboratory display behaviors tending toward the aggressive. They will fight with each other, try to mount female mice and mark their territory with urine. Deprived of testosterone, however, castrated male mice no longer behave so aggressively.

Scientists have long suspected that sex hormones ultimately influence gene expression in the brain-. About six years ago, Shah and his colleagues set out to find such genes by using DNA microarrays, a routine laboratory assay, to analyze sex differences in gene expression in the hypothalamus, a region of the brain known to be involved with hormone sensing.

They found 16 genes that were expressed differently between males and females in the hypothalamus and showed that such differences were regulated by sex hormones. But in identifying these 16 genes, Shah and his colleagues also discovered they could tease apart classic, male and female hormone-driven behaviors into individual elements — each governed by its own genes.

The situation is analogous to the way a house draws its power from the grid. A sex hormone is similar to the main breaker that connects the house to the utility pole and regulates electricity to the entire house.

Individual genes influenced by sex hormones are like the light switches in each room, making it possible to turn the lights on in the kitchen while leaving the bedroom dark.

Sex and Behavior — More than the Sum of Parts?

Much like a main electrical box with many breaker switches, male and female behaviors are actually made up of many behaviors, like sex drive or an inclination to fight. Shah and his colleagues demonstrated this by manipulating the genes separately, sometimes with drugs, to turn them off.

Specifically, they showed that they could selectively knock out some male behaviors so that males continued to fight and mark territory normally but altered their mating routine with females. Likewise they could modulate female mouse behaviors to make them maintain active interest in sex but spend less time caring for their young, or vice versa.

"Other components of male and females behaviors appeared unchanged," Shah said. The implications of this simple observation that a complex human behavior may be composed of numerous genetically controlled elements are both intriguing and daunting, he added. Moreover, it is likely, Shah said, that there are many additional genes that will be discovered to be sex hormone regulated that, in turn, control other components of male or female behaviors.

All authors are at UCSF except Dr. Tetsuro Izumi, who is affiliated with Gunma University in Maebashi, Japan.

This work was funded by the Edward Mallinckrodt, Jr. Foundation, NARSAD, and the National Institutes of Health. Additional support was provided through a National Science Foundation graduate fellowship, a Sandler postdoctoral fellowship, two Genentech graduate fellowships, and an ARCS foundation award.

NewsPsychology (Feb. 2, 2012) — Interventions to promote women have continuously been criticized as ineffective and inhibiting performance. Economists of the University of Innsbruck have now rejected this criticism; they conducted a series of experiments which examined the efficiency and effects of various interventions to increase women’s willingness to enter competition.

The study has been published in Science.

“Many economic studies provide evidence that women tend to opt out of participating in competition even when they are equally or even better qualified than their male colleagues, ” says Univ.-Prof. Matthias Sutter from the Department of Public Finance of the University of Innsbruck. The weaker inclination to enter in competition is one of the reasons why even highly qualified women are at a disadvantage on the labor market regarding promotion opportunities and subsequently wage equality, while their expertise and skills are missing in relevant positions. Companies and public institutions try to counteract by implementing various incentives and interventions. But the actual effects of these policy interventions are still unclear.

“It is nearly impossible to gather reliable field data about this topic,” says Matthias Sutter, who, together with his colleague Loukas Balafoutas, conducted a laboratory experiment with 360 undergraduate students about women’s and men’s immediate reaction to various interventions and how their implementation affects subsequent coordination and teamwork. “Nobody before us had dealt with the question scientifically of how interventions may affect later cooperation within a team even though it is one of the main aspects of the whole discussion,” underlines Sutter this innovative aspect of the study.

Attracting high-performing women to competition

In this multi-stage experiment the subjects were randomly assigned into groups of six each consisting of three men and three women. The task of the subjects was to add as many sets of five two-digit numbers as possible within a timeframe of 3 minutes. The subjects had to choose whether they wanted to be paid for each correct calculation or to receive three times as much per correct calculation if they chose the competitive scheme and were part of the two best performing competitors. Balafoutas and Sutter examined five different competition treatments: In one treatment gender was not taken into account. The second treatment corresponded to a minimum quota regulation, often used in public institutions — there had to be at least one woman among the two winners. In the third treatment women received preferential treatment and automatically received an additional point. In the fourth treatment women were strongly favored by two additional points. Treatment 5 allowed for a repetition of the competition in the case that no woman was among the two winners.

Sutter sums up the main results of the experiment: “Without intervention the number of women willing to compete was only half the number of men. In three of the other four treatments the frequency of competing women is significantly higher, whereas there was no significant effect for men.” The option of repeating the competition was the only treatment that had no significant effect on women’s entry choices. The frequency of women opting to enter competition was particularly high when they were strongly favored. “The most exciting result of the experiment is that, all in all, overall performance did not suffer. Of course, we deducted the additional points from the average performance of the winners and we found that the female winners were qualified enough so that without the additional points they would have performed better or at least as well as their male colleagues,” explains Sutter. “The results of this stage suggest that interventions to support women do indeed have a positive effect, in particular with regard to most highly qualified women.”

Teamwork is not threatened by interventions

In the last stage of the experiment Balafoutas and Sutter examined whether the implementation of interventions to promote women results in a later discrimination when presented with a cooperation task and, thus, in decreased efficiency of team performance. The economists found that none of the interventions affected later teamwork negatively. “We set up a simple coordination game, which was about the efficient coordination of actions, for example, mutual information exchange,” they explain. In this game it was completely clear to all subjects who participated in which intervention beforehand and who the winners were. “It would have been simple to discriminate through inefficient actions against someone who won because of a certain intervention,” says Sutter. “The fact that this did not happen was a surprise.” The scientists hope to be able to eventually confirm their results by field data from the private and the public sector. “But that seems a long way off,” says Sutter.

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The above story is reprinted from materials provided by University of Innsbruck.

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1. L. Balafoutas, M. Sutter. Affirmative Action Policies Promote Women and Do Not Harm Efficiency in the Laboratory. Science, 2012; 335 (6068): 579 DOI: 10.1126/science.1211180

Talk about gender confusion! A recent study by University of Alberta researchers Elena Nicoladis and Cassandra Foursha-Stevenson in the Journal of Cross-Cultural Psychology into whether speaking French influenced how children assigned gender to objects yielded some interesting observations. Nicoladis and Foursha-Stevenson found some differences between the unilingual English children and the bilingual French-English children they surveyed.

Some of the more startling results from the Anglo crowd? Cows are boys. Cats and stars are girls.

Le culture or la culture: our bias

The researchers showed objects or images to the children participating in the study and asked them whether the objects seemed to be masculine or feminine in nature. While the unilingual children seemed to identify most objects as masculine, many younger bilingual children were willing to consider that, globally speaking, some objects could be feminine in nature even though, Nicoladis says, "their categorizations didn't correspond very well to whether the objects were masculine or feminine in French."

As to how Bessie may have inadvertently became Bernie, Nicoladis says that there is an explanation as to why the children may have chosen masculine more often than feminine, even for cows: it reveals a bias embedded in the language.

"Traditionally, in most languages — and English is no exception — the kind of default pronoun is a masculine pronoun," Nicoladis says. "If you read prescriptive grammar books, they might say 'everyone put on his coat' not 'everyone put on his or her coat.' The default, even when the gender isn't specified, is masculine."

No need to check under the hood

These gender-bending statements are no cause for panic. The researchers note that the identity issues were actually relatively common among the unilingual and bilingual kids, with French seeming to have only a small influence with pre-school children.

"What we found is that the monolingual children had a huge boy bias for all of the objects we asked them about," says Nicoladis. "Cats are girls, stars are girls." But to the participants, pretty much everything else was masculine, including cows. To the researchers, it said more about culture and language rather than factual knowledge.

Don't know much about biology…

Nicoladis says that the gender identification is not based on biological knowledge in the younger years. She notes that the older children she surveyed seemed able to reason that cows were the female members of the cattle clan, indicating their understanding of the biology of the animals. And, while some may be tempted to chalk it up to "kids saying the darndest things," some adults seemed to get a little mixed up, too.

"We found the same trends with adults who clearly should be able to reason about the biology," says Nicoladis. "But I think when you're just answering the question really fast, it's picking up some other aspect of their understanding of the world." The embedded bias towards the masculine pronoun was, in effect, trumping the obvious fact that cows are female.

Vive la difference!

Nicoladis says that, with older participants, speaking French seemed to give the kids a different perspective on objects, likely due to the use of masculine and feminine determiners in the language. She notes that the older bilingual children were more apt to identify objects in English as feminine corresponding with their feminine counterparts in the French language, such as: cow/la vache. But she says this is more likely an influence of the structure of the language than it is a reflection of their knowledge of biology.

It's quite possible that the gender in French is making a difference, and not that bilingual children's factual knowledge about cows is any better than that of monolingual children, says Nicoladis. "It's just that the association — how they associate cows — is a little bit changed when they know something about French."

When both male and female college professors have the freedom to take post-birth parental leave, the men almost never do half of the infant care from birth to age 2, even when they believe that child care should be shared equally.

The reason female professors do more infant care may boil down to the fact that they enjoy it more than men do — and that reason may be rooted in evolutionary differences between the sexes, suggests a new, first-of-its-kind study, co-authored by Steven Rhoads, a political scientist in the University of Virginia's College of Arts & Sciences.

The study concludes that gender-neutral policies extending paid post-birth leave to male professors should be re-examined — and possibly repealed.

Paid post-birth leave originally appeared in academia as a way to help level the playing field for women trying to earn tenure while raising children. However, the extension of this benefit to men may actually undermine women's equality in academia, Rhoads said.

Male professors who take paid leave tend to use a majority of their time on things other than infant care, such as advancing their publishing agendas, he said. In contrast, women use the time to do a significant majority of infant care tasks — on top of breastfeeding, perhaps the most time-consuming and physically demanding task.

"In this area, refusal to take sex differences seriously, rather than helping women, leads to a policy that could injure females seeking tenure by giving their male counterparts an unfair advantage," the study concludes. While only about 12 percent of men currently utilize their post-birth leave option, the study finds, "if men should begin to take leave in much larger numbers, far from leveling the playing field, gender-neutral, post-birth leaves are likely to tilt the field further in favor of men."

The study, "Gender Roles and Infant/Toddler Care: Male and Female Professors on the Tenure Track," appears in the January (winter quarter) issue of the Journal of Social, Evolutionary, and Cultural Psychology.

Rhoads is a professor of politics and author of the 2004 best-seller, "Taking Sex Differences Seriously," which argued that sex differences in nurturing, aggression and sex itself are not socially constructed but are instead deeply rooted in biology.

He co-authored the article with his son, Christopher Rhoads, an assistant professor of education at the University of Connecticut.

The study examines how "sticky" gender roles are with respect to infant and toddler care, even when men have the freedom to take parental leave and report believing in non-traditional gender roles. It concludes that neither changing the attitudes of men and women about appropriate gender roles nor offering paternal leave to male professors will bring about equality between the sexes in the division of child care, at least when children are infants or toddlers.

The study is based on a phone survey, conducted in 2001, of 181 married, heterosexual, tenure track professors with children under age 2. The professors were teaching at 40 schools, all of which offered paid parental leave. Twenty-eight schools offered a paid leave benefit equally to fathers and mothers, while the remaining 12 schools had a benefit for mothers only.

The survey's basic data were presented in Chapter 1 of "Taking Sex Differences Seriously," published in 2004, but at that time the data had not yet been fully analyzed or peer reviewed.

Each survey participant was read a sequence of 25 tasks related to the care of a young child — changing diapers, providing care during illness, playing, comforting the child when upset, buying food or toys, providing transportation to day care, etc. — and asked how often he or she performed the task compared to how often his or her spouse performed the task. The simple average of all 25 responses was used as a summary measure of relative performance of child care.

Only three of 109 male faculty members surveyed reported that they did half or more of the care, while 70 of 73 women reported doing at least half. On average, both men and women professors reported that the mother did more than half the work for all 25 of the child care tasks. This result holds even when the male professor's wife works full time.

The female professors also reported higher average enjoyment scores than males on 24 of the 25 child care tasks. (The sole exception was managing the division of labor for parenting tasks, which men disliked less than women.)

Evolution has shaped women to enjoy child care, especially of infants, Steven Rhoads said. Women have hormones that are ideally suited for the nurturing of infants and children, including oxytocin, which is released in large quantities during pregnancy and breastfeeding. Oxytocin promotes bonding and a calm, relaxed emotional state. When nursing releases oxytocin in the mother, it is believed that some of the oxytocin reaches the child through the breast milk, he said. By inducing a mutually pleasurable experience for mother and child, oxytocin increases the feeling of mutual attachment.

Among both monkeys and humans, young females persist in seeking contact with infants even when the mother tries to keep them away. "Women are better than men at the nurturing of young children," Rhoads said. "This superiority is, in large part, biologically based."

Women's enjoyment of child care may also be reinforced by the child's preferences. The survey asked if the child seemed to have a preference about whom he or she played with and who comforted him. There were essentially no differences with respect to playing, but when the babies had a preference, it was overwhelmingly to be comforted by their mothers — by a factor of 14 to 1. Even among men who took leave, the children were twice as likely, by their father's report, to want comfort from their mothers.

"Our results suggest that one reason why female professors do more child care may be that they like it more than men do," the study says. "This conclusion is possible even though the vast majority of female respondents and a clear majority of male respondents believe that husbands and wives should share child care equally. Gender ideology about care may be less important than feelings on these matters."

The study did rely on self-reporting rather than observation, raising issues of reporter bias, as women may feel social pressure to report enjoying child care more than they actually do, Rhoads said. On the other hand, survey interviewers gathered anecdotal evidence that social expectations may also have caused some men to inflate their reports of their child care activity.

"We ought to figure out if there are sex differences, and then figure out what to do about them," he said. "There may be liberal-versus-conservative splits about what to do about them, but it shouldn't be a question whether there are deep-seated sex differences, because that's where the research is pointing."

 Candidates with lower-pitched voices may get more votes in the 2012 election. A new study by biologists and a political scientist shows that both men and women prefer political candidates with deeper voices. The results also suggest that biology — not just partisanship or ideology — can shape voters' choices.

"We often make snap judgments about candidates without full knowledge of their policies or positions. These findings might help explain why," said Duke University biologist Rindy Anderson.

"It's clear that our voices carry more information than the words we speak. Knowing this can help us understand the factors that influence our social interactions and possibly why there are fewer women elected to high-level political positions," she said.

To test voters' preference on voice pitch, Anderson, Duke biologist Susan Peters and University of Miami political scientist Casey Klofstad recorded men and women saying, "I urge you to vote for me this November." The scientists then edited each recording to create a higher- and lower-pitched version of the original.

The team played the recordings of the female voices to 37 men and 46 women at the University of Miami, and the male voices to 49 men and 40 women at Duke. They found that both men and women "elected" the candidates with the lower-pitched voices, regardless of the speaker's gender. The results appear in the March 14 Proceedings of the Royal Society B.

This research is an "interesting first step toward understanding the psychological mechanisms that affect voters' choices," said Brad Verhulst, a researcher at Virginia Commonwealth University in Richmond. He was not involved in the study, but says the experiment is an "exciting application" of previous work on the way visual cues affect people's perceptions of candidates and their competence.

Voice pitch can also affect how people perceive a speaker's competence, honesty and strength, according to past research. But no one had applied that connection to voters' preferences for the voices of both male and female candidates, Anderson said.

In a second experiment, Anderson and her colleagues played the same recordings to three groups of 35 men and 35 women and asked the subjects to select which candidate seemed stronger and more trustworthy and competent.

Both men and women tended to perceive lower-pitched female voices to have all three traits. But only male subjects perceived lower-pitched male voices to be stronger and more competent. They may have been tuned into pitch to gauge the speaker's competitiveness and social aggressiveness, Anderson said.

Women, however, may not discriminate strength and competence in male voices because they are tuning into different cues, vocal or otherwise, to evaluate those traits, she said.

But the findings are based on hypothetical elections conducted in the lab, she said.

"We need to be very careful about interpreting these results in a broader context," Anderson said. The findings raise the possibility that, since women tend to have higher-pitched voices than men, their voice could be one of many different factors that influence gender inequality in leadership roles, she said.

This was a carefully controlled study, Verhulst said. But "until the idea is more thoroughly fleshed out, the broader application to real-world politics is still a conjecture," he said.

As a result, Anderson said she and her collaborators plan to test what they have learned in the laboratory in the 2012 elections.

NewsPsychology (Mar. 8, 2012) — The pulse quickens, the heart pounds and adrenalin courses through the veins, but in stressful situations is our reaction controlled by our genes, and does it differ between the sexes? Australian scientists, writing in BioEssays, believe the SRY gene, which directs male development, may promote aggression and other traditionally male behavioural traits resulting in the fight-or-flight reaction to stress.

Research has shown how the body reacts to stress by activating the adrenal glands which secrete catecholamine hormones into the bloodstream and trigger the aggressive fight-or-flight response. However, the majority of studies into this process have focused on men and have not considered different responses between the sexes.

“Historically males and females have been under different selection pressures which are reflected by biochemical and behavioural differences between the sexes,” said Dr Joohyung Lee, from the Prince Henry’s Institute in Melbourne. “The aggressive fight-or-flight reaction is more dominant in men, while women predominantly adopt a less aggressive tend-and-befriend response.”

Dr Lee and co-author Professor Vincent Harley, propose that the Y-chromosome gene SRY reveals a genetic underpinning for this difference due to its role in controlling a group of neurotransmitters known as catecholamines. Professor Harley’s earlier research had shown that SRY is a sex-determining gene which directs the prenatal development of the testes, which in turn secrete hormones which masculinise the developing body.

“If the SRY gene is absent the testes do not form and the fetus develops as a female. People long thought that SRY’s only function was to form the testes” said Professor Harley. “Then we found SRY protein in the human brain and with UCLA researchers led by Professor Eric Vilain, showed that the protein controls movement in males via dopamine.”

“Besides the testes, SRY protein is present in a number of vital organs in the male body, including the heart, lungs and brain, indicating it has a role beyond early sex determination,” said Dr Lee. “This suggests SRY exerts male-specific effects in tissues outside the testis, such as regulating cardiovascular function and neural activity, both of which play a vital role in our response to stress.”

The authors propose that SRY may prime organs in the male body to respond to stress through increased release of catecholamine and blood flow to organs, as well as promoting aggression and increased movement which drive fight-or-flight in males. In females oestrogen and the activation of internal opiates, which the body uses to control pain, may prevent aggressive responses.

The role of SRY regulation of catecholamines also suggests the gene may have a role in male-biased disorders such as Parkinson’s disease.

“New evidence indicates that the SRY gene exerts ‘maleness’ by acting directly on the brain and peripheral tissues to regulate movement and blood pressure in males,” concluded Lee. “This research helps uncover the genetic basis to explain what predisposes men and women to certain behavioural phenotypes and neuropsychiatric disorders.”

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The above story is reprinted from materials provided by Wiley-Blackwell.

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Journal Reference:

1. Joohyung Lee, Vincent R. Harley. The male fight-flight response: A result of SRY regulation of catecholamines? BioEssays, 2012; DOI: 10.1002/bies.201100159

Although women continue to lag behind men in pay, the gender wage gap has narrowed considerably since the 1960s. Now a new University of Michigan study is the first to quantify the impact of the pill on women's labor market advances.

The study shows that roughly one-third of women's wage gains through the 1990s are due to the availability of oral contraceptives.

Published online this week by the National Bureau of Economic Research as a working paper, the study was conducted by U-M economist Martha Bailey and colleagues Brad Hershbein at U-M and Amalia Miller at the University of Virginia.

"We found that women who had early access to the pill in the 1960s and 1970s earned 8 percent more on average by the 1980s and 1990s than women without early access," said Bailey, an assistant professor of economics in the U-M College of Literature, Science, and the Arts and a research affiliate at the U-M Institute for Social Research.

Bailey and colleagues analyzed the careers of approximately 4,300 women, born from 1943 to 1954, using the National Longitudinal Survey of Young Women. These women varied in their legal ability to obtain the pill from their doctors between the ages of 18 and 21

"The difficulty of parsing the pill's effect on women's careers relates to the timing of its appearance," Bailey said. "By cause or coincidence, the pill's diffusion coincided with important changes in norms and ideas about women's work and the end of the baby boom."

Bailey and colleagues developed a novel analytic strategy to answer this question. After the U.S. Federal Drug Administration approved the pill in 1960, laws in different states placed different age limits on when women could legally obtain it. As these laws changed in almost every state in the country, largely due to reducing the legal voting age to 18, the inadvertent side-effect was that women could obtain the pill at younger ages. This meant that women no longer had to decide between looking for a mate (and the risk of pregnancy) and investing in their educations and careers. They could do both.

The researchers found that early access laws doubled contraceptive pill use among women between the ages of 18 and 20 – precisely the ages affected by access laws – but not beyond age 21, when the laws did not bind. Pill use by age 18 was 140 percent higher, and by age 20 was 43 percent higher than national mean use at those ages.

"As the pill provided younger women the expectation of greater control over childbearing, women invested more in their human capital and careers," Bailey said. "Most affected were women with some college, who benefitted from these investments through remarkable wage gains over their lifetimes."

Their analysis shows that nearly two-thirds of these pill-access induced gains in wages were due to increasing labor-market experience; another third came through to greater educational attainment and entry in non-traditionally female occupations.

But even these results may not do justice to the over-arching importance of the pill.

"Our results may understate the pill's broader influence because they do not explore the effect of changes in access to the pill beyond age 20 and fail to capture the potentially large social multiplier effects," Bailey said. "The pill's availability likely altered norms and expectations about marriage and childbearing. It also likely affected the decisions of companies to hire and promote women."

The Opt-In Revolution? Contraception and the Gender Gap in Wages

NewsPsychology (Apr. 4, 2012) — A study based on the National Health and Sexuality Survey, involving nearly 2000 people, describes the sexual practices of senior citizens in Spain. The most common are kisses, caresses and vaginal penetration. The main causes of sexual inactivity are physical illness and widowerhood.

A new study published in The Journal of Sexual Medicine analyses the factors that influence sexual activity amongst elderly people in Spain.

“This research lets us know the reality of a social phenomenon which is not tackled enough in Spain: sexuality and the elderly,” Domingo Palacios, a researcher at the Rey Juan Carlos University in Madrid and main author of this study, explained.

The results, based on the National Health and Sexuality Survey, in which 1,939 heterosexual elderly people participated in 2009, show that 62.3% of men and 37.4% of women are sexually active. The most common practices are kisses, caressing and vaginal penetration. On the other hand, the least practised are masturbation and oral sex.

Furthermore, there are other factors that limit sexual activity in both sexes: being older than 75, not having a partner, having a low level of education, a poor perception of their own health and sexuality, suffering from two or more chronic illnesses and taking two or more types of medication.

“This can be applied to preventing illnesses and promoting health and healthy sexual practices,” Palacios states. He highlights widowerhood and physical illness amongst reasons why the older Spanish population do not have sexual intercourse.

The authors note gender differences among those older than 65, with less sexual activity in women compared to men. They also note age differences, with better results for those aged between 65 and 74 than those older than 75.

The results support previous studies

This is not the first time that sexual health amongst the elderly has been measured. In 2006, a study published during the XXVI Spanish Family and Community Medicine Society (SEMFYC) Conference showed that 60% of people over the age of 65 said they had sex on average four times a month.

In that project, which was carried out with over 100 people by family doctors in Catalonia, the majority said that although their sexual intercourse had changed as a result of age, they were not “less satisfying.”

Furthermore, new data backs up a survey carried out in the USA and published in New England Journal of Medicine in 2008, in which 73% of Americans between 57 and 64 years of age had sex. The number dropped to 53% for those aged between 65 and 75, and dropped to 26% for those aged 85.

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The above story is reprinted from materials provided by Plataforma SINC, via AlphaGalileo.

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1. Domingo Palacios-Ceña, Pilar Carrasco-Garrido, Valentín Hernández-Barrera, Cristina Alonso-Blanco, Rodrigo Jiménez-García, César Fernández-de-las-Peñas. Sexual Behaviors among Older Adults in Spain: Results from a Population-Based National Sexual Health Survey. The Journal of Sexual Medicine, 2012; 9 (1): 121 DOI: 10.1111/j.1743-6109.2011.02511.x

Prejudice against people from groups different than their own is linked to aggression for men and fear for women, suggests new research led by Michigan State University scholars.

The researchers report that, throughout history, men have been the primary aggressors against different groups as well as the primary victims of group-based aggression and discrimination.

"There is evidence going back thousands of years of bands of men getting together and attacking other bands of men, eliminating them and keeping the women as the spoils of war," said Carlos David Navarrete, evolutionary psychologist at MSU.

As modern examples, Navarrete noted the wars in Central Africa and the Balkans that were marred by rape and genocide.

Navarrete co-authored the study with MSU researcher Melissa McDonald and Mark Van Vugt of the University of Amsterdam and the University of Oxford. The research appears in Philosophical Transactions of the Royal Society B, a London-based research journal.

The researchers analyzed current academic literature on war and conflict and found that the standard social science theory did not explain the sex differences in aggressive or discriminatory behavior between groups. They offered a novel theory that integrates psychology with ecology and evolutionary biology. Their "male warrior hypothesis" explains how a deep evolutionary history of group conflict may have provided the backdrop for natural selection to shape the social psychologies and behaviors of men and women in fundamentally distinct ways.

Essentially, men are more likely to start wars and to defend their own group, sometimes in very risky and self-sacrificial ways. Attacking other groups represents an opportunity to offset these costs by gaining access to mates, territory, resources and increased status.

The authors complement these findings with results from lab experiments showing that men are more prejudiced toward other groups.

Women, meanwhile, live under the threat of sexual coercion by foreign aggressors, and are apt to display a "tend-and-befriend response" toward members of their own group, while maintaining a fear of strangers in order to protect themselves and their offspring.

"Although these sex-specific responses may have been adaptive in ancestral times," said McDonald, the lead author of the study, "they have likely lost this adaptive value in our modern society, and now act only to needlessly perpetuate discrimination and conflict among groups.

Navarrete added that the behavior is seen in humans' closest relative, the chimpanzee. "Just like humans, they'll attack and kill the males of other groups. They'll also attack females — not to the point of killing them, but more to get them to join their group," he said.

Since the behaviors are common among both humans and chimps, they are likely to have existed in our common ancestor millions of years ago, Navarrete said.

"This would have provided eons of time for the deepest workings of our minds to have been fundamentally shaped by these cruel realities," he said. "Coming to grips with this history and how it still affects us in modern times may be an important step into improving the problems caused by our darker predispositions."

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Journal Reference:

1. M. M. McDonald, C. D. Navarrete, M. Van Vugt. Evolution and the psychology of intergroup conflict: the male warrior hypothesis. Philosophical Transactions of the Royal Society B: Biological Sciences, 2012; 367 (1589): 670 DOI: 10.1098/rstb.2011.0301

 Women report more intense pain than men in virtually every disease category, according to Stanford University School of Medicine investigators who mined a huge collection of electronic medical records to establish the broad gender difference to a high level of statistical significance.

Their study, published online in the Journal of Pain, suggests that stronger efforts should be made to recruit women subjects in population and clinical studies in order to find out why this gender difference exists.

The study also shows the value of EMR data mining for research purposes. Using a novel database designed especially for research, the Stanford scientists examined more than 160,000 pain scores reported for more than 72,000 adult patients. From these, they extracted cases where disease-associated pain was first reported, and then stratified these findings by disease and gender.

"None of these data were initially collected for research, but this study shows that we can use it in that capacity," said Atul Butte, MD, PhD, the study's senior author.

The medical literature contains numerous reports indicating that women report more pain than men for one or another particular disease, noted Butte, a professor of systems medicine in pediatrics. "We're certainly not the first to find differences in pain among men and women. But we focused on pain intensity, whereas most previous studies have looked at prevalence: the percentage of men vs. women with a particular clinical problem who are in pain. To the best of our knowledge, this is the first-ever systematic use of data from electronic medical records to examine pain on this large a scale, or across such a broad range of diseases."

The study's first authors were Butte's graduate student Linda Liu and postdoctoral scholar David Ruau, PhD, who splits his time between Butte's group and that of co-author Martin Angst, MD, professor of anesthesia. David Clark, MD, PhD, a professor of anesthesia, was another co-author.

Electronic medical records are deployed in about 1-2 percent of hospitals now, but that should approach 100 percent within the next few years as the United States continues to move toward EMRs, Butte said. Thus, large-scale research using clinically collected data will become increasingly feasible.

In this case, the scientists tapped an existing data archive that has been designed specifically for ease of research: the Stanford Translational Research Integrated Database Environment, or STRIDE. Pioneered by the medical school's chief information officer, Henry Lowe, MD (who is also an associate professor of systems medicine in pediatrics and director of Stanford's Center for Clinical Informatics), STRIDE aggregates clinical data on patients cared for at Stanford Hospital & Clinics and Lucile Packard Children's Hospital, making this data searchable for approved research projects.

Butte's team selected only adult records and looked for gender-related differences in pain intensity as reported on 1-to-10 scales, in which a zero stands for "no pain" and 10 for "worst imaginable." Their search algorithm combed through de-identified EMR data for more than 72,000 patients, and came up with more than 160,000 instances, ranging across some 250 different disease categories, in which a pain score had been reported.

"If someone's reporting that they're in pain, they're probably going to be given medication, which might reduce any subsequently measured pain score," said Butte. To get pain estimates that weren't as confounded by subsequent pain-relief medications or procedures, his group analyzed only the first pain-intensity score reported by a patient per encounter with a hospital-associated health professional.

The search identified 47 separate diagnostic categories for which there were more than 40 pain reports for each gender. The sample included more than 11,000 individual adult patients, of which 56 percent were women and 51 percent of them white. The researchers were able to further analyze these 47 categories by condensing them into 16 disease clusters: "musculoskeletal and connective tissue" (in which the biggest gender differences in reported pain intensity were observed), "circulatory" and so forth.

"We saw higher pain scores for female patients practically across the board," said Butte. Those reported differences were not only statistically significant, but also clinically significant. "In many cases, the reported difference approached a full point on the 1-to-10 scale. How big is that? A pain-score improvement of one point is what clinical researchers view as indicating that a pain medication is working."

While the overall results tended to confirm previous clinical findings — for example, that female fibromyalgia or migraine patients report more pain than their male counterparts — the search also unearthed previously unreported gender differences in pain intensity for particular diseases, for example acute sinusitis and "cervical spine disorders," more commonly known as neck pain.

The study's results come with a few caveats. First, the investigators made the assumption that patients' pain hadn't already been treated — for example, that they hadn't already self-medicated with over-the-counter painkillers — by the time they showed up in the emergency room, doctor's office or neighborhood health clinic (or, equivalently, that the men and women were equally likely to have done so).

Other possible confounders include the setting in which pain was reported, Butte said. "Will an 18-year-old male report the same pain intensity with or without his mom present, or in the presence of a male vs. a female nurse? We can't be sure." But the sheer size of the study probably washes these concerns out at least to some extent, he said.

The third caveat is perhaps the most controversial. "It's still not clear if women actually feel more pain than men do," said Butte. "But they're certainly reporting more pain than men do. We don't know why. But it's not just a few diseases here and there, it's a bunch of them — in fact, it may well turn out to be all of them. No matter what the disease, women appear to report more-intense levels of pain than men do."

To get to the bottom of this, Butte's team plans to search EMRs to see if they can find some objective measurement — an already commonly measured blood-test variable, for instance — that correlates highly with reported pain. "We want to find a biomarker for pain," he said.

The work was funded by the Stanford Institute for Immunity, Transplantation and Infection; the National Library of Medicine; the Hewlett-Packard Foundation; and the Lucile Packard Foundation for Children's Health.

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Journal Reference:

1. David Ruau, Linda Y. Liu, J. David Clark, Martin S. Angst, Atul J. Butte. Sex Differences in Reported Pain Across 11,000 Patients Captured in Electronic Medical Records. The Journal of Pain, 2012; DOI: 10.1016/j.jpain.2011.11.002