Chapter 8. Hormones and Sex
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By Helen Briggs Health editor, BBC News website The timing of when a girl reaches puberty is controlled by hundreds of genes, say scientists. And age at first period may vary in daughters from the same family because of genetic factors, research shows. The findings, published in Nature, could give clues to why early puberty may be linked to an increased risk of health conditions. Scientists at 166 institutions analysed the DNA of more than 180,000 women in one of the largest studies of its kind. They found that hundreds of genes were involved in the timing of puberty. Unusually, a girl's first period was also influenced by imprinted genes - a rare event where genes from either the mother of father are silenced. "Our findings imply that in a family, one parent may more profoundly affect puberty timing in their daughters than the other parent," said lead researcher Dr John Perry of the University of Cambridge. He said the biological complexity revealed in the study was "amazing". "We identified more than 100 regions of the genome associated with puberty timing, but our analysis suggests there are likely to be thousands," he told BBC News. Lifestyle BBC © 2014
By Katherine Harmon Courage Octopuses do the darndest things. Like kill their mate during mating—by strangling him with three arms, according to new observations from the wild. Enterprising scientists Christine Huffard and Mike Bartick watched wild octopuses in action. They found that, for males, mating can be a dangerous game. Especially when your lady has long limbs. Some of the more dicey encounters are detailed in a new paper, published online July 11 in Molluscan Research. Hold on a second, you say. Strangling octopuses? Octopuses don’t even have necks—or inhale air. So how, exactly, does that work? The strangulation seems to happen when “an octopus wraps at least one arm around the base of the mantle of the competitor” (or mate), Huffard wrote in 2010. This constriction then keeps the octopus from taking in fresh water to run past its gills—starving the animal of its oxygen source. Octopuses are not known to get cuddly with one another on a day-to-day basis. In fact, “octopuses touch each other with their arms primarily in the context of mating and aggression,” the researchers write. And in this case it seems to have been both. Huffard came across a pair of mating day octopuses (Octopus cyanea) near Fiabacet Island in Indonesia. The female, as is often the case in this species, was larger—with a body about seven-and-a-half inches long; the male was closer to six inches long. They were positioned on a reef, outside the female’s den, the male’s mating arm (hectocotylus) inserted into the female’s mantle from a (presumably) safe distance. © 2014 Scientific American
Keyword: Sexual Behavior
Link ID: 19869 - Posted: 07.23.2014
By JAN HOFFMAN As it has for decades, the Centers for Disease Control and Prevention last week released its annual National Health Interview Survey on the health of Americans. But this year, there was a difference: For the first time, the respondents were asked about their sexual orientation. Of 34,557 adults ages 18 and older, the survey reported, 1.6 percent said they were gay or lesbian. Some critics say the numbers are low, but they fall in the range of other surveys. In the new survey, however, only 0.7 percent of respondents described themselves as bisexual; other studies have reported higher numbers. Adults who identified themselves as gay, lesbian or bisexual reported some different behaviors and concerns — for example, more alcohol consumption and cigarette smoking — than those who said they were straight. But it can be difficult to elicit information that many people consider private. The New York Times spoke about such challenges with Gary J. Gates, a demographer at the Williams Institute at the U.C.L.A. School of Law, which focuses on law and policy issues related to sexual orientation and gender identity. Some of Dr. Gates’s findings were echoed in the new survey. This interview was edited and condensed. Q.How was this survey conducted? A.Survey takers had a computer that guided them through questions which they asked the respondent in person, and they used flash cards to show them potential answers. Q.Why do you think the figure for bisexuality was lower than in other surveys? A.There is evidence that bisexuals perceive more stigma and discrimination than gay and lesbian people. They are much less likely to tell important people around them that they are bisexual. © 2014 The New York Times Company
Keyword: Sexual Behavior
Link ID: 19862 - Posted: 07.22.2014
By Joel Achenbach Friends often look alike. The tendency of people to forge friendships with people of a similar appearance has been noted since the time of Plato. But now there is research suggesting that, to a striking degree, we tend to pick friends who are genetically similar to us in ways that go beyond superficial features. For example, you and your friends are likely to share certain genes associated with the sense of smell. Our friends are as similar to us genetically as you’d expect fourth cousins to be, according to the study published Monday in the Proceedings of the National Academy of Sciences. This means that the number of genetic markers shared by two friends is akin to what would be expected if they had the same great-great-great-grandparents. “Your friends don’t just resemble you superficially, they resemble you genetically,” said Nicholas A. Christakis, a physician and social scientist at Yale University and a co-author of the study. The resemblance is slight, just about 1 percent of the genetic markers, but that has huge implications for evolutionary theory, said James Fowler, a professor of medical genetics and political science at the University of California at San Diego. “We can do better than chance at predicting if two people are going to be friends if all we have is their genetic data,” Fowler said. This is a data-driven study that covers hundreds of friendship pairs and stranger pairs, plus hundreds of thousands of genetic markers. There’s no single “friendship” gene driving people together. There’s no way to say that a person befriended someone else because of any one genetic trait.
By ALEX STONE Last summer, in a failed attempt at humor, Clorox ran an online ad that declared, “Like dogs or other house pets, new dads are filled with good intentions but lacking the judgment and fine motor skills to execute well.” Although the company pulled the ad amid a flurry of scorn from the online commentariat, it nevertheless played to a remarkably widespread stereotype — that fathers are somehow unfit to raise children. In “Do Fathers Matter?” — spoiler alert: they do — the veteran science writer Paul Raeburn jumps to Dad’s defense, drawing on several decades of research and his own experience as a five-time father. What emerges is a thought-provoking field piece on the science of fatherhood, studded with insights on how to apply it in the real world. Historically, developmental psychologists have largely dismissed fathers as irrelevant. Nearly half the articles on child and adolescent psychology published in leading journals from 1997 to 2005, for example, make no mention of fathers; before 1970, when fathers weren’t even allowed in delivery rooms, less than a fifth of the research on parental bonding took them into account. This bias reflects a deeply ingrained assumption that fathers play a marginal role in how their children turn out, a belief enshrined in the theory of infant attachment, which grew out of the work of the British psychiatrist John Bowlby in the second half of the 20th century. “It focused exclusively on mothers,” Mr. Raeburn writes. “The role of the father, Bowlby believed, was to provide support for the mother. In the drama of childhood, he was merely a supporting actor.” This was more or less the established view until a few decades ago, when psychologists, motivated in part by the growing number of women entering the work force, finally started paying attention to fathers. © 2014 The New York Times Company
|By William Skaggs Jet lag is a pain. Besides the inconvenience and frustration of traveling more than a few time zones, jet lag likely causes billions of dollars in economic losses. The most effective treatment, according to much research, is structured exposure to light, although the drug melatonin may also sometimes be helpful at bedtime. Both approaches have been used for more than 20 years, and during that time no viable new interventions have appeared. Recently, however, research into the molecular biology of circadian rhythms has raised the prospect of developing new drugs that might produce better results. Jet lag occurs when the “biological clock” in the brain becomes misaligned with the local rhythm of daily activity. The ultimate goal of circadian medicine is a treatment that instantly resets the brain's clock. Failing that, it would be helpful to have treatments that speed the rate of adjustment. Four recent discoveries suggest new possibilities. The first involves vasopressin, which is the main chemical signal used to synchronize cellular rhythms of activity in the brain area that is responsible for our biological clock. Blocking vasopressin makes it much easier to reset this clock. Potentially, a drug that interferes with vasopressin could work as a fast-acting treatment for jet lag. The second and third possibilities involve a pair of brain chemicals called salt-inducible kinase 1 (SIK1) and casein kinase 1ε (CK1ε), both of which limit the ability of light to reset the brain's clock. Drugs already exist that interfere with their action and greatly increase the effectiveness of light exposure. The existing drugs are not viable jet-lag treatments, because they are hard to administer and have unpleasant side effects, but researchers hope better drugs can be developed that work in a similar way. © 2014 Scientific American,
By Virginia Morell Many moth species sing courtship songs, and until now, scientists knew of only two types of such melodies. Some species imitate attacking bats, causing a female to freeze in place, whereas others croon tunes that directly woo the ladies. But the male yellow peach moth (Conogethes punctiferalis, pictured) belts out a combination song, scientists report online today in the Proceedings of the Royal Society B. These tiny troubadours, which are found throughout Asia, emit ultrasonic refrains composed of short and long pulses by contracting their abdominal tymbals, sound-producing membranes. (Listen to a male’s courtship song above.) The short pulses, the scientists say, are similar to the hunting calls of insectivorous horseshoe bats. However, unlike other moth species, these males aren’t directing the batlike tunes at females, but rather at rival males. Using playback experiments, the scientists showed that a male drives away competitors with the short pulses of his ditty, while inducing a female to mate with the long note. Indeed, a receptive virgin female moth (1 to 3 days old) typically raises her wings after hearing this part of the male’s song—a sign that she accepts the male, the scientists say. It is thus the first moth species known to have a dual-purpose melody. © 2014 American Association for the Advancement of Science
By LISA SANDERS, M.D. On Wednesday, we challenged Well readers to solve the case of a middle-aged woman who suddenly began to have episodes of confusion caused by low blood sugars. Her endocrinologist thought she might have an insulinoma, an insulin-producing tumor of the pancreas, but the testing he did seemed to rule out that diagnosis. Nearly 200 of you took on the challenge of trying to figure out what was causing her life-threatening drops in blood sugar level. The correct diagnosis is… Insulinoma The first respondent to make the diagnosis was Karen Unkel of Kinder, La. She is not a doctor but has a longstanding interest in hypoglycemia that allowed her to recognize the disease even in the face of an apparently negative work-up. Well done, Ms. Unkel. An insulinoma is a rare tumor of pancreatic tissue that makes and secretes insulin independently of blood glucose levels. This results in episodes of hypoglycemia that can be quite severe, even life-threatening. The diagnosis is suspected when a patient fulfills what is known as Whipple’s triad: 1) symptoms of hypoglycemia 2) associated with low measured blood sugar and 3) which improve when blood sugar is raised to the normal range. The diagnosis is made when doctors show that the patient is making too much insulin given his or her blood sugar level. Measuring insulin levels is not always accurate because insulin is processed rapidly in the body and because it is difficult to distinguish between insulin made naturally in the pancreas and any insulin that the patient might be injecting. What is measured instead is something known as C-peptide. Insulin is first made as a larger molecule known as proinsulin. When blood sugar rises, an extra bit is shaved off the molecule; that extra bit is C-peptide, and both the resulting insulin and C-peptide are released into the bloodstream. © 2014 The New York Times Company
Karen Ravn To the west, the skies belong to the carrion crow. To the east, the hooded crow rules the roost. In between, in a narrow strip running roughly north to south through central Europe, the twain have met, and mated, for perhaps as long as 10,000 years. But although the crows still look very different — carrion crows are solid black, whereas hooded crows are grey — researchers have found that they are almost identical genetically. The taxonomic status of carrion crows (Corvus corone) and hooded crows (Corvus cornix) has been debated ever since Carl Linnaeus, the founding father of taxonomy, declared them to be separate species in 1758. A century later, Darwin called any such classification impossible until the term 'species' had been defined in a generally accepted way. But the definition is still contentious, and many believe it always will be. The crows are known to cross-breed and produce viable offspring, so lack the reproductive barriers that some biologists consider essential to the distinction of a species, leading to proposals that they are two subspecies of carrion crow. In fact, evolutionary biologist Jochen Wolf from Uppsala University in Sweden and his collaborators have now found that the populations living in the cross-breeding zone are so similar genetically that the carrion crows there are more closely related to hooded crows than to the carrion crows farther west1. Only a small part of the genome — less than 0.28% — differs between the populations, the team reports in this week's Science1. This section is located on chromosome 18, in an area associated with pigmentation, visual perception and hormonal regulation. It is no coincidence, the researchers suggest, that the main differences between carrion and hooded crows are in colouring, mating preferences (both choose mates whose colouring matches theirs), and hormone-influenced social behaviours (carrion crows lord it over hooded ones). © 2014 Nature Publishing Group,
by Laura Sanders Some brain cells need a jolt of stress to snap to attention. Cells called astroglia help regulate blood flow, provide energy to nearby cells and even influence messages’ movement between nerve cells. Now, scientists report June 18 in Neuron that astroglia can be roused by the stress molecule norepinephrine, an awakening that may help the entire brain jump into action. As mice were forced to walk on a treadmill, an activity that makes them alert, astroglia in several parts of their brains underwent changes in calcium levels, a sign of activity, neuroscientist Dwight Bergles of Johns Hopkins University School of Medicine and colleagues found. Norepinephrine, which acts as a fight-or-flight hormone in the body and a neural messenger in the brain, seemed to cause the cell activity boost. When researchers depleted norepinephrine, treadmill walking no longer activated astroglia. It’s not clear whether astroglia in all parts of the brain heed this wake-up call, nor is it clear whether this activation influences behavior. Norepinephrine might help shift brain cells, both neurons and astroglia, into a state of heightened vigilance, the authors write. © Society for Science & the Public 2000 - 2013.
By PAM BELLUCK Cindy Wachenheim was someone people didn’t think they had to worry about. She was a levelheaded lawyer working for the State Supreme Court, a favorite aunt who got down on the floor to play with her nieces and nephews, and, finally, in her 40s, the mother she had long dreamed of becoming. But when her baby was a few months old, she became obsessed with the idea that she had caused him irrevocable brain damage. Nothing could shake her from that certainty, not even repeated assurances from doctors that he was normal. “I love him so much, but it’s obviously a terrible kind of love,” she agonized in a 13-page handwritten note. “It’s a love where I can’t bear knowing he is going to suffer physically and mentally/emotionally for much of his life.” Ms. Wachenheim’s story provides a wrenching case study of one woman’s experience with maternal mental illness in its most extreme and rare form. It also illuminates some of the surprising research findings that are redefining the scientific understanding of such disorders: that they often develop later than expected and include symptoms not just of depression, but of psychiatric illnesses. Now these mood disorders, long hidden in shame and fear, are coming out of the shadows. Many women have been afraid to admit to terrifying visions or deadened emotions, believing they should be flush with maternal joy or fearing their babies would be taken from them. But now, advocacy groups on maternal mental illness are springing up, and some mothers are blogging about their experiences with remarkable candor. A dozen states have passed laws encouraging screening, education and treatment. And celebrities, including Brooke Shields, Gwyneth Paltrow and Courteney Cox, have disclosed their postpartum depression. © 2014 The New York Times Company
By Denali Tietjen Caffeine isn’t healthy, but that’s no news. The withdrawal headaches, jitteriness and dehydration kind of gave that one way. What is news, however, is that starting at puberty, it’s worse for boys than girls. Girls and boys have the same cardiovascular reactions to caffeine in childhood, but begin to react differently in adolescence, finds a new study conducted by researchers from The University of Buffalo. In the double-blind study published in the June issue of Pediatrics, researchers examined the cardiovascular reactions of 52 pre-pubescent (ages eight to nine) and 49 post-pubescent (ages 15 to 17) children to varying levels of caffeine. Participants consumed either the placebo, 1 mg/kg or 2 mg/kg caffeinated sodas, and then had their heart rates and blood pressures taken. The results found that pre-pubescent children had the same reaction to caffeine regardless of gender, while post-pubescent boys had much stronger cardiovascular reactions to caffeine than girls. The study also examined post-pubescent girls’ reactions to caffeine at various phases of their menstrual cycles. At different stages of the cycle, the girls metabolized caffeine differently. “We found differences in responses to caffeine across the menstrual cycle in post-pubertal girls, with decreases in heart rate that were greater in the mid-luteal phase and blood pressure increases that were greater in the mid-follicular phase of the menstrual cycle,” Dr. Jennifer Temple, one of the researchers who conducted the study said in a University at Buffalo press release announcing the study.
by Bethany Brookshire Human vocal chords can produce an astonishing array of sounds: shrill and fearful, low and sultry, light and breathy, loud and firm. The slabs of muscle in our throat make the commanding sound of a powerful bass and a baby’s delightful, gurgling laugh. There are voices that must be taken seriously, voices that play and voices that seduce. And then there’s vocal fry. Bringing to mind celebrity voices like Kim Kardashian or Zooey Deschanel, vocal fry is a result of pushing the end of words and sentences into the lowest vocal register. When forcing the voice low, the vocal folds in the throat vibrate irregularly, allowing air to slip through. The result is a low, sizzling rattle underneath the tone. Recent studies have documented growing popularity of vocal fry among young women in the United States. But popular sizzle in women’s speech might be frying their job prospects, a new study reports. The findings suggest that people with this vocal affectation might want to hold the fry on the job market — and that people on the hiring side of the table might want to examine their biases. Vocal fry has been recognized since the 1970s, but now it’s thought of as a fad. Study coauthor Casey Klofstad, a political scientist at the University of Miami in Goral Gables, Fla., says that the media attention surrounding vocal fry generated a lot of speculation. “It is a good thing? Is it bad? It gave us a clear question we could test,” he says. Specifically, they wanted to study whether vocal fry had positive or negative effects on how people who used the technique were perceived. Led by Rindy Anderson from Duke University, the researchers recorded seven young men and seven young women speaking the phrase “Thank you for considering me for this opportunity.” Each person spoke the phrase twice, once with vocal fry and once without. Then the authors played the recordings to 800 participants ages 18 to 65, asking them to make judgments about the candidates based on voice alone. © Society for Science & the Public 2000 - 2013
Virginia Morell If we humans inhale oxytocin, the so-called “love hormone,” we become more trusting, cooperative, and generous. Scientists have shown that it’s the key chemical in the formation of bonds between many mammalian species and their offspring. But does oxytocin play the same role in social relationships that aren’t about reproduction? To find out, scientists in Japan sprayed either oxytocin or a saline spray into the nostrils of 16 pet dogs, all more than 1 year old. The canines then joined their owners, who were seated in another room and didn’t know which treatment their pooch had received. The owners were instructed to ignore any social response from their dogs. But those Fidos that inhaled the oxytocin made it tough for their masters not to break the rule. A statistical analysis showed the canines were more likely to sniff, lick, and paw at their people than were those given the saline solution. The amount of time that the oxytocin-enhanced dogs spent close to their owners, staring at their eyes, was also markedly higher, the scientists report online today in the Proceedings of the National Academy of Sciences. Getting a whiff of oxytocin also made the dogs friendlier toward their dog pals as determined by the amount of time they spent in close proximity to their buddies. The study supports the idea, the scientists say, that oxytocin isn’t just produced in mammals during reproductive events. It’s also key to forming and maintaining close social relationships—even when those are with unrelated individuals or different species. © 2014 American Association for the Advancement of Science.
Keyword: Hormones & Behavior
Link ID: 19716 - Posted: 06.10.2014
By Jenny Graves The claim that homosexual men share a “gay gene” created a furor in the 1990s. But new research two decades on supports this claim – and adds another candidate gene. To an evolutionary geneticist, the idea that a person’s genetic makeup affects their mating preference is unsurprising. We see it in the animal world all the time. There are probably many genes that affect human sexual orientation. But rather than thinking of them as “gay genes,” perhaps we should consider them “male-loving genes.” They may be common because these variant genes, in a female, predispose her to mate earlier and more often and to have more children. Likewise, it would be surprising if there were not “female-loving genes” in lesbian women that, in a male, predispose him to mate earlier and have more children. We can detect genetic variants that produce differences between people by tracking traits in families that display differences. Patterns of inheritance reveal variants of genes (called “alleles”) that affect normal differences, such as hair color, or disease states, such as sickle cell anemia. Quantitative traits, such as height, are affected by many different genes, as well as environmental factors. It’s hard to use these techniques to detect genetic variants associated with male homosexuality partly because many gay men prefer not to be open about their sexuality. It is even harder because, as twin studies have shown, shared genes are only part of the story. Hormones, birth order and environment play roles, too.
Ian Sample, science correspondent Research on children in Denmark has found that boys with autism were more likely to have been exposed to higher levels of hormones in their mother's wombs than those who developed normally. Boys diagnosed with autism and related disorders had, on average, raised levels of testosterone, cortisol and other hormones in the womb, according to analyses of amniotic fluid that was stored after their mothers had medical tests during pregnancy. The findings add to a growing body of evidence that the biological foundations of autism are laid down well before birth and involve factors that go beyond the child's genetic make-up. The results may help scientists to unravel some of the underlying causes of autism and explain why boys are four to five times more likely to be diagnosed with the condition, which affects around one percent of the population. Amniotic fluid surrounds babies in the womb and contains hormones and other substances that they have passed through their urine. The liquid is collected for testing when some women have an amniocentesis around four months into their pregnancy. Scientists in Cambridge and Copenhagen drew on Danish medical records and biobank material to find amniotic fluid samples from 128 boys who were later diagnosed with autism. Compared to a control group, the boys with autism and related conditions had higher levels of four "sex steroid" hormones that form a biological production line in the body that starts with progesterone and ends with testosterone. "In the womb, boys produce about twice as much testosterone as girls, but compared with typical boys, the autism group has even higher levels. It's a significant difference and may have a large effect on brain development," said Simon Baron-Cohen, director of the Autism Research Centre at Cambridge University. © 2014 Guardian News and Media Limited
By MARK OPPENHEIMER When our young daughters first decided to play on top of our Honda minivan, parked in our driveway, my wife was worried. But to me, it seemed no less safe than chasing a ball that frequently ended up in the street. And they loved the height, the novelty, the danger. So I let them stay. They never fell. And with the summer weather here, playing on the car is once again keeping them occupied for hours. Now that I have read Paul Raeburn’s “Do Fathers Matter?,” I know that my comfort with more dangerous play — my willingness to let my daughters stand on top of a minivan — is a typically paternal trait. Dads roughhouse with children more, too. They also gain weight when their wives are pregnant and have an outsize effect on their children’s vocabulary. The presence of dads can delay daughters’ puberty. But older dads have more children with dwarfism and with Marfan syndrome. In Mr. Raeburn’s book, there is plenty of good news for dads, and plenty of bad. A zippy tour through the latest research on fathers’ distinctive, or predominant, contributions to their children’s lives, “Do Fathers Matter?” is filled with provocative studies of human dads — not to mention a lot of curious animal experiments. (You’ll learn about blackbirds’ vasectomies.) But above all, Mr. Raeburn shows how little we know about the role of fathers, and how preliminary his book is. Its end is really a beginning, a prospectus for further research. Mr. Raeburn writes that “as recently as a generation ago, in the 1970s, most psychologists” believed that “with regard to infants, especially, fathers were thought to have little or no role to play.” When it came to toddlers and older children, too, the great parenting theories of the 20th century placed fathers in the background. Freud famously exalted, or damned, the mother for her influence. John Bowlby’s attachment theory, which he developed beginning in the 1940s, focused on the mother or “mother-figure.” © 2014 The New York Times Company
Keyword: Sexual Behavior
Link ID: 19686 - Posted: 06.03.2014
By NICHOLAS BAKALAR The hormone estrogen is the recommended treatment for menopausal night sweats and hot flashes, but some women are unable or unwilling to use it. Now a clinical trial suggests that the antidepressant venlafaxine, often used as an alternative, is equally effective. In an eight-week placebo-controlled double-blind study, researchers randomly assigned 339 perimenopausal and postmenopausal women to one of three treatments: 0.5 milligrams a day of estrogen (in the form of estradiol), 75 milligrams a day of the antidepressant venlafaxine (a generic form of Effexor), or a placebo. Before the start of the study, all the women had had symptoms at least 14 times a week. Compared to the rate before the study — an average of 8.1 episodes a day — the frequency of hot flashes and night sweats declined by 52.9 percent in the estradiol group, 47.6 percent in the Effexor group, and 28.6 percent among those who took a placebo. Both Effexor and estradiol were effective treatments, but the study, published online in JAMA Internal Medicine, was not large enough to show that one was significantly better than the other. “Women have important choices of different medications to discuss with their doctors,” said the lead author, Dr. Hadine Joffe, an associate professor of psychiatry at Harvard. “They should know, as they think about these options, that both are effective.” © 2014 The New York Times Company
Keyword: Hormones & Behavior
Link ID: 19673 - Posted: 05.31.2014
By Denali Tietjen If you watch porn, you probably have a small brain, a new study published in the Journal of the American Medical Association (JAMA) shows. The study, conducted by the Max Plank Institute for Human Development in Berlin, found a significant negative correlation between frequent pornography consumption and grey matter in the brain (that’s the stuff that tells your brain how to react to sensory information.) The keyword here is correlation. While the study’s findings are significant, the researchers don’t know if it’s the porn that causes the low grey-matter volume in porn-watchers, or if it’s the other way around. It could be a neurological pre-condition that makes watching porn particularly satisfying. However, researchers have reason to believe that porn does negatively impact the brain. Previous research proves that frequent porn consumption can cause negative social behavior. Porn consumption can cause viewers to be less satisfied during sex and viewers often want to adopt acts they’ve seen in illegal pornography, according to the report. If porn can affect social behavior, it can probably affect cognitive behavior, too. The study examined the cognitive structure of 64 males ages 21 to 45 years old that consumed porn at varying levels of frequency. While few people openly admit to watching porn, 66 percent of all men and 41 percent of American women view pornography at least once a month, and an estimated 50 percent of internet traffic is sex-related, according to the journal.
Elizabeth Norton Cultures around the world have long assumed that women are hardwired to be mothers. But a new study suggests that caring for children awakens a parenting network in the brain—even turning on some of the same circuits in men as it does in women. The research implies that the neural underpinnings of the so-called maternal instinct aren't unique to women, or activated solely by hormones, but can be developed by anyone who chooses to be a parent. "This is the first study to look at the way dads' brains change with child care experience," says Kevin Pelphrey, a neuroscientist at Yale University who was not involved with the study. "What we thought of as a purely maternal circuit can also be turned on just by being a parent—which is neat, given the way our culture is changing with respect to shared responsibility and marriage equality." The findings come from an investigation of two types of households in Israel: traditional families consisting of a biological mother and father, in which the mother assumed most of the caregiving duties, though the fathers were very involved; and homosexual male couples, one of whom was the biological father, who'd had the child with the help of surrogate mothers. The two-father couples had taken the babies home shortly after birth and shared caregiving responsibilities equally. All participants in the study were first-time parents. Researchers led by Ruth Feldman, a psychologist and neuroscientist at Bar-Ilan University in Ramat Gan, Israel, visited with the families in their homes, videotaping each parent with the child and then the parents and children alone. The team, which included collaborators at the Tel Aviv Sourasky Medical Center in Israel, also took saliva samples from all parents before and after the videotaped sessions to measure oxytocin—a hormone that's released at times of intimacy and affection and is widely considered the "trust hormone.” Within a week of the home visit, the participants underwent functional magnetic resonance imaging scanning to determine how their brains reacted to the videotapes of themselves with their infants. © 2014 American Association for the Advancement of Science