Chapter 8. Hormones and Sex
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
David Cox In the spring of 1930, Danish artist Einar Wegener arrived in Berlin for a consultation that he hoped would both save and change his life. Wegener had spent the previous twenty years dressing as a woman, Lili Elbe. In public, his wife, painter Gerda Gottlieb, introduced Elbe as Wegener’s sister . But by 1930 he could not bear his double life any longer. He resolved to commit suicide, even naming a date – May 1. Instead, Wegener made a different choice, electing to undergo a series of pioneering gender reassignment operations, transitioning into Lili Ilse Elvenes, better known as Lili Elbe. Elbe’s extraordinary story remains controversial; indeed, the film The Danish Girl, starring Eddie Redmayne and based on Elbe’s life was this week banned from Qatari cinemas after protests about its “depravity”. Elbe’s revolutionary transition would not have been possible without the contribution of the sexologist Magnus Hirschfeld, a man who had become both renowned and notorious across Europe for his groundbreaking research into human gender and sexuality. While Elbe’s posthumous 1933 biography, “Man into Woman: The First Sex Change”, made her story internationally famous, Hirschfeld is a less well-known figure today. As both a Jew and gay activist, much of his legacy was burnt to ashes when his Institute for Sexual Research was targeted by a Nazi attack in 1933. But through colleagues and pupils, his work has gone on to transform the way we view sexual minorities and has helped make gender reassignment surgery the widely accepted procedure it is today. © 2016 Guardian News and Media Limited o
Keyword: Sexual Behavior
Link ID: 21786 - Posted: 01.14.2016
Eva Emerson Chronic stress takes its toll on everyone. But it may hit women harder (or at least differently) than men, much research finds. New studies in rodents show that females remain sensitive to ongoing stress longer than males do, as Susan Gaidos reports. It remains to be seen whether such results can explain the differences in rates of depression and anxiety disorders in men and women. (Perhaps women are more likely to discuss their symptoms and be diagnosed. Men, on the other hand, are more likely to abuse drugs and alcohol, disorders which may also be related to stress.) Still, the new work offers an intriguing idea: If stress induces distinct biochemical signaling in men and women, perhaps therapies should also be tailored to each sex. Another fascinating line of research mentioned in Gaidos’ story involves altering female mice’s response to chronic stress (making it more like a male’s) by targeting DNA modifications known as epigenetic tags. Consisting of chemicals such as methyl groups, these tags are attached to DNA and influence gene activity. They seem like a perfect target for drugs. Epigenetic tags don’t change the underlying genes, just the instructions for turning those genes on or off, up or down. In the mice, scientists used enzymes to alter the chemical tags on genes involved in the response to chronic stress. It’s an exciting approach, one I’m sure many scientists will try in efforts to modulate the body’s response, not just to stress, but also to other threats to health. Maybe even to fat. A woman’s extra fat can trigger metabolic changes in a developing fetus, Laura Beil reports. Beil describes the latest research about the risks faced by children of obese moms or moms who have gained too much weight while pregnant. Neurological effects are the new twist, and a scary one, given the prevalence of obesity among women of childbearing age. © Society for Science & the Public 2000 - 2015
By Virginia Morell When you hear a bird warbling, you probably think the crooner is a male. And chances are if you’re in the Northern Hemisphere, you would be right. But females also evolved to sing, and many still do—although generally less than the males. One reason may be that it’s more dangerous for them to sing especially when nesting, scientists report today. At least, that’s the case for female fairywrens, the most vocal of which are the most likely to have their eggs and chicks eaten. The study “provides some of the first field evidence indicating why females of so many songbird species might have lost song,” says Karan Odom, a Ph.D. candidate at the University of Maryland, Baltimore, and the lead author of a 2014 study on the evolution of birdsong. Female superb fairywrens (Malarus cyaneus)—a small Australian species—aren’t the only female songbirds that sing. In fact, females sing in 71% of songbird species, often for territorial defense. In species like the superb fairywren, some females even sing when they’re on their nests, a place where, at least theoretically, they should pipe down so as not to attract predators. Rodents, birds, cats, and foxes have all been seen preying on the fairywrens’ nests. “People had observed [this singing in the nest behavior], but they hadn’t investigated it,” says Sonia Kleindorfer, a behavioral ecologist at Flinders University in Adelaide, Australia. “It struck me as odd, and very risky.” © 2016 American Association for the Advancement of Science
Susan Gaidos Muscles tighten, the heart pounds and nausea takes hold: In the face of sudden stress, men and women respond alike. But when threats, scares or frustrations continue for days or months, differences between the sexes emerge. Scientists have long known that women are more likely than men to suffer depression, post-traumatic stress disorder and other anxiety disorders, all of which have been linked to chronic stress, says Temple University psychologist Debra Bangasser. But until recently, studies of people’s responses to such stress have focused primarily on men. Now, a growing number of scientists are studying what happens at the cellular and genetic levels in the brains of stressed-out rodents — male and female — to gain insight into the human brain. The studies are beginning to reveal differences between the sexes that may help explain the variability in their reactions and perhaps even provide much-needed insight into why stress-related disorders are more common in women than men. Recent findings reported at the annual meeting of the Society for Neuroscience, held in Chicago in October, show that a common stress hormone triggers different responses in specific brain cells of male and female animals. The differences make females less able than males to adapt to chronic stress. Other studies are exploring how exposure to the same hormone influences gene expression in a part of the brain that controls mood and behavior. Still other research suggests that a different hormone, associated with trust, could render females more susceptible than males to depression, anxiety and PTSD. © Society for Science & the Public 2000 - 2015.
By Darryl Fears Flushed down toilets, poured down sinks and excreted in urine, a chemical component in the pill wafts into sewage systems and ends up in various waterways where it collects in fairly heavy doses. That's where fish soak it up. A recent survey by the U.S. Geological Survey found that fish exposed to a synthetic hormone called 17a-ethinylestradiol, or EE2, produced offspring that struggled to fertilize eggs. The grandchildren of the originally exposed fish suffered a 30 percent decrease in their fertilization rate. The authors mulled the impact of what they discovered and decided it wasn't good. "If those trends continued, the potential for declines in overall population numbers might be expected in future generations," said Ramji Bhandari, a University of Missouri assistant research professor and a visiting scientist at USGS. "These adverse outcomes, if shown in natural populations, could have negative impacts on fish inhabiting contaminated aquatic environments." The study, with Bhandari as lead author, also determined that the chemical BPA, used widely in plastics, had a similar effect on the small Japanese medaka fish used for the research. The medaka was chosen because it reproduces quickly so that scientists can see results of subsequent generations faster than slow reproducing species such as smallmouth bass.
Katherine Hobson Pregnant women worry about all kinds of things. Can I drink alcohol? (No.) Can I take antidepressants? (Maybe.) Can I do the downward dog? (Yes.) Now there's one less thing to fret about: harm to the baby when the mother takes birth control pill right before conceiving, or during the first few months of pregnancy. According to a study covering more than 880,000 births in Denmark, the overall rate of birth defects was consistent for women who had never taken the pill at all, for those who had used it before getting pregnant and for those who continued on the pill in early pregnancy. (There were about 25 birth defects per 1,000 births for all groups.) The study is important because so many women take the pill – about 16 percent of women of childbearing age in the U.S. When used perfectly, the failure rate of the pill is less than 1 percent, but that jumps to 9 percent under typical use because of missed pills, drug interactions or illness. That means a lot of embryos are exposed to the hormones used in the pill, which can linger for a few months after a woman stops taking it. "Our findings are really reassuring," says Brittany Charlton, an author of the study and a researcher in the Harvard T.H. Chan School of Public Health's epidemiology department. The results also confirm most of the previous research, which has pointed to no overall increase in major birth defects, she says. This study, published in the medical journal BMJ, used national birth, patient and prescription registry data to track contraceptive prescriptions among women who gave birth, then looked at whether birth defects were associated with pill use. © 2016 npr
By Debra W. Soh What should parents do if their little boy professes an intense desire to be a girl? Or if their daughter comes home from kindergarten and says she wants to be a boy? In recent years the dominant thinking has changed dramatically regarding children’s gender dysphoria. Previously, parents might hope that it would be a passing phase, as it usually is. But now they are under pressure from gender-identity politics, which asserts that children as young as 5 should be supported in wanting to live as the opposite sex. Any attempts to challenge this approach are deemed intolerant and oppressive. I myself was a gender-dysphoric child who preferred trucks and Meccano sets to Easy-Bake Ovens. I detested being female and all of its trappings. Yet when I was growing up in the 1980s, the concept of helping children transition to another sex was completely unheard of. My parents allowed me to wear boys’ clothing and shave my head, to live as a girl who otherwise looked and behaved like a boy. I outgrew my dysphoria by my late teens. Looking back, I am grateful for my parents’ support, which helped me work things out. Since then, research has established best-treatment practices for adolescents and adults with gender dysphoria: full transitioning, which includes treatment with hormones to suppress puberty and help the individual develop breasts or facial hair, as well as gender-reassignment surgery. But prepubescent children who identify with the opposite sex are another matter entirely. How best to deal with them has become so politicized that sexologists, who presumably would be able to determine the healthiest approach, are extremely reluctant to get involved. They have seen what happens when they deviate from orthodoxy. ©2016 Dow Jones & Company, Inc
By Darryl Fears For male smallmouth bass, sex change is increasingly not an option. In the chemical-laced Chesapeake Bay watershed and in rivers up through New England, it comes with the territory. Based on the latest U.S. Geological Survey on intersex fish, 85 percent of male smallmouth bass in waters in and around national wildlife refuges in the Northeast have developed "characteristics of the opposite sex." That's in addition to 90 percent of the species in some West Virginia waters and 50 percent to 100 percent in the southern stretch of the Potomac River. All of the affected fish had eggs where their testes should be, according to previous studies. Why this is happening remains a mystery, says the lead author of a new study, despite the problem being detected more than a decade ago. “It is not clear what the specific cause of intersex is in these fish,” said Luke Iwanowicz, a USGS research biologist. “This study was designed to identify locations that may warrant further investigation." The strongest suspicion focuses on what is poured down the drains of homes, businesses and farms every day. Scientists are worried that prescription drugs such as birth control and mood-control pharmaceuticals, flushed down toilets, and chemical pesticides such as atrazine, washed off farms by rain, have turned creeks, streams and rivers into chemical soups that disrupt the endocrines of marine life.
By Roni Caryn Rabin Melatonin has been shown to be effective in randomized clinical trials — the kind considered the gold standard in medicine — but it may work better for some sleep problems than others. “There is pretty strong evidence it’s effective for jet lag,” said D. Craig Hopp, a program director at the National Center for Complementary and Integrative Health, part of the National Institutes of Health. But “the evidence is more equivocal for chronic things like insomnia.” A 2002 Cochrane review that analyzed 10 randomized trials, most of them comparing oral melatonin to placebo, concluded that melatonin is “remarkably effective in preventing or reducing jet lag.” It not only helped people fall asleep faster and sleep more soundly, but also led to less daytime fatigue and improved general well-being. Eight of the 10 trials found that taking melatonin for several days after arriving at a destination reduced jet lag from flights crossing at least five time zones. In many of the trials, people also took melatonin on the day of the flight or for several days before the trip, usually in the late afternoon or early evening. Once at the destination, melatonin should be taken close to bedtime, aiming for the local hours between 10 p.m. and midnight. Doses of 0.5 milligrams and 5 milligrams were both effective, though people fell asleep faster and slept better with the larger dose. For others with insomnia, melatonin has more modest benefits. A 2013 analysis that looked at 19 randomized controlled trials involving 1,683 subjects determined that on average, melatonin reduced the amount of time it took to fall asleep by seven minutes when compared with placebo and increased total sleep time by eight minutes. © 2015 The New York Times Company
Love a sugar hit? Your sweet tooth may hail from an unlikely source: your liver. A hormone made by the organ appears to control how much carbohydrate and sugar we want to eat, and helps slow us down when we are overindulging. The hormone, called FGF21, has already been found to help obese mice lose weight and regain their sensitivity to insulin. A modified form is currently in clinical trials to test whether it has the same effect in people with diabetes. Our bodies break down carbohydrates into sugars such as sucrose, glucose and fructose. Recent genetic studies have suggested that people with altered levels of FGF21 consume more carbohydrates. To find out more, a team co-led by Matthew Potthoff at the University of Iowa observed the eating habits of mice with either abnormally high or low levels of the hormone. They found that mice genetically modified to lack the hormone chose to drink much higher levels of sugar-sweetened drinks than normal mice. Those given an extra dose of the hormone, on the other hand, reduced their sugar intake. The team also showed that the hormone is produced in response to high carbohydrate levels; it then enters the bloodstream, where it sends a signal to the brain to suppress our sugar intake. In people, blood levels of FGF21 triple 24 hours after a spike in blood sugar levels. When monkeys were given the synthetic version of the hormone being tested in clinical trials, they also opted for a diet low in sugar, according to a separate study by Steven Kliewer at the University of Texas Southwestern Medical Center at Dallas and colleagues. The team also found that these monkeys consumed less alcohol than those that weren’t given the compound. © Copyright Reed Business Information Ltd.
By Gary Stix A lingering question asked by neuroscientists has to do with what, if anything, makes the male and female brain distinctive, whether in mice or (wo)men. There is still no concise answer. The best evidence from the most recent research suggests that both males and females share the same neural circuitry, but use it differently. Catherine Dulac, a professor of molecular and cellular biology at Harvard, and investigator at the Howard Hughes medical Institute, is a pioneer in exploring these questions. I talked to her briefly about her research, which also extends far beyond just the neurobiology of gender. Can you tell me in broad overview about what you study? I'm interested in understanding how the brain engages in instinctive social behaviors. There are a lot of instinctive behaviors such as eating and sleeping that are essential in animals and humans, but social behavior is a very distinctive and particularly interesting set of instinctive behaviors that we would like to understand at the neuronal level. What we would like to understand in mechanistic terms is how does an individual recognize other animals of its own species, for example how does an animal identifies a male, a female, or an infant, how does the brain processes these signals in order to trigger appropriate social behaviors such as mating, aggression or parenting. Can you tell me a little bit about your work of the last few years that relates to gender identification? © 2015 Scientific American
By Katrina Schwartz It has become a cultural cliché that raising adolescents is the most difficult part of parenting. It’s common to joke that when kids are in their teens they are sullen, uncommunicative, more interested in their phones than in their parents and generally hard to take. But this negative trope about adolescents misses the incredible opportunity to positively shape a kid’s brain and future life course during this period of development. “[Adolescence is] a stage of life when we can really thrive, but we need to take advantage of the opportunity,” said Temple University neuroscientist Laurence Steinberg at a Learning and the Brain conference in Boston. Steinberg has spent his career studying how the adolescent brain develops and believes there is a fundamental disconnect between the popular characterizations of adolescents and what’s really going on in their brains. Because the brain is still developing during adolescence, it has incredible plasticity. It’s akin to the first five years of life, when a child’s brain is growing and developing new pathways all the time in response to experiences. Adult brains are somewhat plastic as well — otherwise they wouldn’t be able to learn new things — but “brain plasticity in adulthood involves minor changes to existing circuits, not the wholesale development of new ones or elimination of others,” Steinberg said. Adolescence is the last time in a person’s life that the brain can be so dramatically overhauled. © 2015 KQED Inc.
By BENEDICT CAREY Dr. Robert L. Spitzer, who gave psychiatry its first set of rigorous standards to describe mental disorders, providing a framework for diagnosis, research and legal judgments, as well as a lingua franca for the endless social debate over where to draw the line between normal and abnormal behavior, died on Friday. He was 83. From Our Advertisers Dr. Spitzer died from complications of heart disease at the assisted living facility where he lived in Seattle, his wife, Janet Williams, said. The couple had moved to Seattle from Princeton, N.J., this year. Dr. Spitzer’s remaking of psychiatry began with an early interest in one of the least glamorous and, historically, most ignored corners of the field: measurement. In the early 1960s, the field was fighting to sustain its credibility, in large part because diagnoses varied widely from doctor to doctor. For instance, a patient told he was depressed by one doctor might be called anxious or neurotic by another. The field’s diagnostic manual, at the time a pamphlet-like document rooted in Freudian ideas, left wide latitude for the therapist’s judgment. Dr. Spitzer, a rising star at Columbia University, was himself looking for direction, increasingly frustrated with Freudian analysis. A chance meeting with a colleague working on a new edition of the manual — the Diagnostic and Statistical Manual of Mental Disorders, or the D.S.M. for short — led to a job taking notes for the committee debating revisions. There, he became fascinated with reliable means for measuring symptoms and behavior — i.e., assessment. “At the time, there was zero interest in assessment,” said Dr. Michael First, a professor of clinical psychiatry at Columbia. “He saw how important it was, and his whole career led to assessment being taken seriously.” © 2015 The New York Times Company
By Francine Russo Some children insist, from the moment they can speak, that they are not the gender indicated by their biological sex. So where does this knowledge reside? And is it possible to discern a genetic or anatomical basis for transgender identity? Exploration of these questions is relatively new, but there is a bit of evidence for a genetic basis. Identical twins are somewhat more likely than fraternal twins to both be trans. Male and female brains are, on average, slightly different in structure, although there is tremendous individual variability. Several studies have looked for signs that transgender people have brains more similar to their experienced gender. Spanish investigators—led by psychobiologist Antonio Guillamon of the National Distance Education University in Madrid and neuropsychologist Carme Junqué Plaja of the University of Barcelona—used MRI to examine the brains of 24 female-to-males and 18 male-to-females—both before and after treatment with cross-sex hormones. Their results, published in 2013, showed that even before treatment the brain structures of the trans people were more similar in some respects to the brains of their experienced gender than those of their natal gender. For example, the female-to-male subjects had relatively thin subcortical areas (these areas tend to be thinner in men than in women). Male-to-female subjects tended to have thinner cortical regions in the right hemisphere, which is characteristic of a female brain. (Such differences became more pronounced after treatment.) “Trans people have brains that are different from males and females, a unique kind of brain,” Guillamon says. “It is simplistic to say that a female-to-male transgender person is a female trapped in a male body. It's not because they have a male brain but a transsexual brain.” Of course, behavior and experience shape brain anatomy, so it is impossible to say if these subtle differences are inborn. © 2015 Scientific American
By David Shultz As the Rolling Stones, Revlon, and Angelina Jolie can attest, not many body parts are more sexualized than the lips. A new study published online today in Royal Society Open Science, suggests that we’re not the only primates that feel this way. Black-and-white snub-nosed monkeys (Rhinopithecus bieti, pictured) have a strict social hierarchy in which a few, older males mate with multiple females, while the younger males form bachelor groups and bide their time. The males’ lips naturally redden with age, but the story seems a little more complicated than that: A series of photographs taken over multiple months shows that mating males’ lips redden during the mating season, whereas the bachelor males’ become paler. Scientists still aren’t sure why the animals’ lips seem to correspond with their social rank, but one idea is that females prefer the redder shades when choosing a mate, similar to how a female peacock chooses the male with the most elaborate tail. Another explanation could be that the males are using lip color as a preemptive indicator of their status in order to minimize conflict: Paler lips could make bachelors appear less threatening, allowing the mating males to focus their aggression on other red-lipped competitors. Both mechanisms could also be acting simultaneously, the authors say. © 2015 American Association for the Advancement of Science.
Keyword: Sexual Behavior
Link ID: 21703 - Posted: 12.16.2015
By SINDYA N. BHANOO Prairie voles are small Midwestern rodents known for monogamous behavior. But some males are also known to stray and seek out other females. A new study reports that mating preferences in the voles are linked to genetic differences, and that both monogamous and nonmonogamous males are readily found in nature. The study appears in the journal Science. Generally, animal neuroscientists believe that natural selection minimizes genetic variation. In this case, however, one mating strategy does not seem to be more successful than the other. Monogamous males stay near their nests, which ensures that female mates remain faithful. Promiscuous males have more partners, but they also lose sight of their own mates. “When you roam, your own female is free to mate with whoever she wants,” said Steven M. Phelps, a neurobiologist at the University of Texas at Austin and one of the study’s authors. The genetic differences between nonmonogramous and monogamous males affect a part of the brain important for spatial memory. Good memory may help a male keep track of his mate or keep him from returning to a hostile male’s territory. “We’ve shown for the first time that not only can brains be variable, but natural selection can keep that variability around,” Dr. Phelps said. © 2015 The New York Times Company
By Andrea Anderson Mom's ovaries could hold clues to some autism cases, new research suggests—and this time it's not because of genetic vulnerabilities carried in her eggs. A new, large-scale study out of Sweden suggests that women with polycystic ovarian syndrome (PCOS)—an endocrine disorder that affects 5 to 10 percent of women of childbearing age—have an increased risk of giving birth to children with autism spectrum disorder (ASD). The Karolinska Institute's Renee Gardner, along with colleagues from Sweden and the U.S., tapped into a Swedish national population health database to look at potential ties between PCOS and ASD. As they reported online December 8 in Molecular Psychiatry, the team looked at 23,748 individuals with ASD and nearly 209,000 unaffected individuals, all born in Sweden between 1984 and 2007. Although identifying information about the individuals was removed, the researchers had access to information about their relationships to others in the database as well as documented diagnoses and use of health care services. The group found that ASD was 59 percent more prevalent in children born to women with PCOS—a relationship that was independent of PCOS complications such as increased neonatal distress or C-section delivery. This risk level is roughly comparable with that of having a father over age 50 (estimated to be 66 percent) but lower than it is in those with certain rare genetic syndromes or mutations. The authors of the analysis believe PCOS increases ASD risk in offspring to a greater extent than maternal infection, one of many factors previously implicated in autism. © 2015 Scientific American
By Ariana Eunjung Cha Attention-deficit/hyperactivity disorder is often thought of a boy thing. In explaining the jump in cases in recent years, numerous researchers, educators and parents have theorized that perhaps boys are hardwired to be more impulsive, wiggly and less able to stay on task in the early years than their female counterparts. That may be a myth. A study published in The Journal of Clinical Psychiatry on Tuesday shows a surprising 55 percent increase in prevalence of diagnoses among girls — from 4.7 percent to 7.3 percent from 2003 to 2011. The rise in cases in girls mirrors a similar but less-sharp rise in cases in boys from a prevalence of 11.8 to 16.5 percent. During the same period, the researchers found an increase in cases across all races and ethnicities but especially in Hispanic children. In all children, the prevalence increased from 8.4 percent to 12 percent. The analysis, conducted by George Washington University biostatistician Sean D. Cleary and his co-author Kevin P. Collins of Mathematica Policy Research, was based on data from the National Survey of Children's Health in which parents were asked whether they had been told by a doctor or other health care provider that their child has ADHD.
Laura Sanders Taking a pregnancy hormone staves off multiple sclerosis relapses, a small clinical trial suggests. The results hint at a potential therapy for women who suffer from MS, a debilitating disease in which the body’s immune system attacks the insulation that wraps around nerve cell fibers. A curious observation kicked off this line of research: Pregnancy offers a temporary reprieve for women with MS. Since that discovery, in the 1990s, scientists have been testing whether certain pregnancy hormones might combat MS in women who aren’t pregnant. In addition to a standard MS drug, 164 women with MS received either a placebo or estriol, an estrogen made by the placenta that peaks toward the end of pregnancy. After two years, women who received estriol had an average of 0.25 relapses a year, while women who received the placebo had 0.37 relapses a year, UCLA neurologist Rhonda Voskuhl and colleagues write online November 24 in Lancet Neurology. Researchers don’t know whether estriol would have similar effects in men with MS. The results warrant a larger clinical trial, the authors say. An accompanying commentary in the same issue of Lancet Neurology questions the results, though. MS specialist Annette Langer-Gould of Kaiser Permanente in Pasadena, Calif., raises methodological issues and writes that pregnancy comes with a host of changes that could be responsible for protection from MS. © Society for Science & the Public 2000 - 2015.
You may have read that having a male brain will earn you more money. Or maybe that female brains are better at multitasking. But there is no such thing as a female or male brain, according to the first search for sex differences across the entire human brain. It reveals that most people have a mix of male and female brain features. And it also supports the idea that gender is non-binary, and that gender classifications in many situations are meaningless. “This evidence that human brains cannot be categorised into two distinct classes is new, convincing, and somehow radical,” says Anelis Kaiser at the University of Bern, Switzerland. The idea that people have either a “female” or “male” brain is an old one, says Daphna Joel at Tel Aviv University in Israel. “The theory goes that once a fetus develops testicles, they secrete testosterone which masculinises the brain,” she says. “If that were true, there would be two types of brain.” To test the theory, Joel and her colleagues looked for differences in brain scans taken from 1400 people aged between 13 and 85. The team looked for variations in the size of brain regions as well as the connections between them. In total, the group identified 29 brain regions that generally seem to be different sizes in self-identified males and females. These include the hippocampus, which is involved in memory, and the inferior frontal gyrus, which is thought to play a role in risk aversion. When the group looked at each individual brain scan, however, they found that very few people had all of the brain features they might be expected to have, based on their sex. Across the sample, between 0 and 8 per cent of people had “all-male” or “all-female” brains, depending on the definition. “Most people are in the middle,” says Joel. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 21670 - Posted: 12.01.2015