Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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By BENEDICT CAREY and PAM BELLUCK He was a graduate student who seemingly had it all: drive, a big idea and the financial backing to pay for a sprawling study to test it. In 2012, as same-sex marriage advocates were working to build support in California, Michael LaCour, a political science researcher at the University of California, Los Angeles, asked a critical question: Can canvassers with a personal stake in an issue — in this case, gay men and women — actually sway voters’ opinions in a lasting way? He would need an influential partner to help frame, interpret and place into context his findings — to produce an authoritative scientific answer. And he went to one of the giants in the field, Donald P. Green, a Columbia University professor and co-author of a widely used text on field experiments. “I thought it was a very ambitious idea, so ambitious that it might not be suitable for a graduate student,” said Dr. Green, who signed on as a co-author of Mr. LaCour’s study in 2013. “But it’s such an important question, and he was very passionate about it.” Last week, their finding that gay canvassers were in fact powerfully persuasive with people who had voted against same-sex marriage — published in December in Science, one of the world’s leading scientific journals — collapsed amid accusations that Mr. LaCour had misrepresented his study methods and lacked the evidence to back up his findings. On Tuesday, Dr. Green asked the journal to retract the study because of Mr. LaCour’s failure to produce his original data. Mr. LaCour declined to be interviewed, but has said in statements that he stands by the findings. © 2015 The New York Times Company
Keyword: Sexual Behavior
Link ID: 20979 - Posted: 05.26.2015
Richard A. Friedman AMERICANS disapprove of marital infidelity. Ninety-one percent of them find it morally wrong, more than the number that reject polygamy, human cloning or suicide, according to a 2013 Gallup poll. Yet the number of Americans who actually cheat on their partners is rather substantial: Over the past two decades, the rate of infidelity among married men has been pretty constant at around 21 percent, while the percentage of married women who admitted to cheating has mostly hovered between 10 and 15 percent, according to the General Social Survey at the University of Chicago’s independent research organization, NORC. We are accustomed to thinking of sexual infidelity as a symptom of an unhappy relationship, a moral flaw or a sign of deteriorating social values. When I was trained as a psychiatrist we were told to look for various emotional and developmental factors — like a history of unstable relationships or a philandering parent — to explain infidelity. But during my career, many of the questions we asked patients were found to be insufficient because for so much behavior, it turns out that genes, gene expression and hormones matter a lot. Now that even appears to be the case for infidelity. We have long known that men have a genetic, evolutionary impulse to cheat, because that increases the odds of having more of their offspring in the world. But now there is intriguing new research showing that some women, too, are biologically inclined to wander, although not for clear evolutionary benefits. Women who carry certain variants of the vasopressin receptor gene are much more likely to engage in “extra pair bonding,” the scientific euphemism for sexual infidelity. © 2015 The New York Times Company
By SINDYA N. BHANOO Male Java sparrows are songbirds — and, scientists reported on Wednesday, natural percussionists. The sparrows click their bills against a hard surface while singing. That clicking is done in coordination with the song, much as a percussion instrument accompanies a melody. Researchers at Hokkaido University in Japan observed the birds producing clicks frequently toward the beginning of their songs and around specific notes. Birds that were related produced similar percussive patterns, but whether this behavior is learned or innate is unclear. Next the scientists, who described their findings on Wednesday in the journal PLOS One, would like to know whether male sparrows use bill clicks during courtship communication. © 2015 The New York Times Company
by Karl Gruber "As clever as a guppy" is not a huge compliment. But intelligence does matter to these tropical fish: big-brained guppies are more likely to outwit predators and live longer than their dim-witted peers. Alexander Kotrschal at Stockholm University, Sweden, and his colleagues bred guppies (Poecilia reticulata) to have brains that were bigger or smaller than average. His team previously showed that bigger brains meant smarter fish. When put in an experimental stream with predators, big-brained females were eaten about 13 per cent less often than small-brained ones. There was no such link in males, and the researchers suspect that their bright colours may counter any benefits of higher intelligence. They did find, Kotrschal says , that large-brained males were faster swimmers and better at learning and remembering the location of a female. "This is exciting because it confirms a critical mechanism for brain size evolution," says Kotrschal. It shows, he adds, that interactions between predator and prey can affect brain size. It might seem obvious that bigger brains would help survival. Yet previous research simply found a correlation between the two, leaving the possibility open that some third factor may have been driving the effect. Now, direct brain size manipulation allowed Kotrschal's team to pin it down as a cause of better survival. "This is the first time anyone has tested whether a larger brain confers a survival benefit," says Kotrschal. "The fact that large-brained females survived better in a naturalistic setting is the first experimental proof that a larger brain is beneficial for the fitness of its bearer. This is like watching evolution happen and shows how brain size evolves." © Copyright Reed Business Information Ltd.
Alexandra Sifferlin Autism, already a mysterious disorder, is even more puzzling when it comes to gender differences. For every girl diagnosed with autism, four boys are diagnosed, a disparity researchers don’t yet fully understand. In a new study published in the journal Molecular Autism, researchers from the UC Davis MIND Institute tried to figure out a reason why. They looked at 112 boys and 27 girls with autism between ages 3 and 5 years old, as well as a control sample of 53 boys and 29 girls without autism. Using a process called diffusion-tensor imaging, the researchers looked at the corpus callosum — the largest neural fiber bundle in the brain — in the young kids. Prior research has shown differences in that area of the brain among people with autism. They found that the organization of these fibers was different in boys compared with girls, especially in the frontal lobes, which play a role in executive functions. “The sample size is still limited, but this work adds to growing body of work suggesting boys and girls with autism have different underlying neuroanatomical differences,” said study author Christine Wu Nordahl, an assistant professor in the UC Davis Department of Psychiatry and Behavioral Sciences, in an email. In other preliminary research presented at the International Meeting for Autism Research, or IMFAR, in Salt Lake City, the study authors showed that when girls and boys with autism are compared with typically developing boys and girls, the behavioral differences between girls with autism and the female controls are greater than the differences among the boys. Nordahl says this suggests that girls can be more severely affected than boys.
Margaret Wente Child psychiatrist Susan Bradley was a pioneer in treating kids with gender-identity disorders. In the 1970s, she founded the child and adolescent gender identity clinic at the Clarke Institute in Toronto, which eventually became part of the Centre for Addiction and Mental Health (CAMH). Back then, the field was virtually unknown. Today, it is Ground Zero in a fierce battle between oldfangled psychiatry and transgender activists who insist that practitioners like Dr. Bradley are guilty of child abuse. Caught in the middle are confused parents, well-meaning schools, and – most important of all – troubled and bewildered kids. The new rush to turn little Jason into Janey, or Sally into Sam, is generally regarded (in the media, at least) as progress – proof of what a tolerant and progressive society we’ve become. But what if it’s just another fad? What if the radical step of changing genders isn’t always the right answer for a child’s emotional distress – especially when that child is only 10 or 6, or 3? “Some of these kids are quite significantly ill,” says Dr. Bradley. “They often have serious family problems and anxiety disorders. Or they’ve had serious trauma. A girl I saw had been raped, and after that she decided she was going to be a male. If you didn’t pay attention to the trauma you’re not doing that kid a service.” These days, that eminently reasonable view is being challenged by people who believe that children’s sexual confusion should automatically be taken at face value. The clinic that Dr. Bradley helped to found – which does, in fact, support gender transition for a sizable minority of its patients – is being pilloried as transphobic. “Is CAMH trying to turn trans kids straight?” screamed a headline in NOW magazine. Under pressure from activists, CAMH has put its gender clinic under six-month review. And a new bill before the Ontario legislature, which is supported by Premier Kathleen Wynne, would explicitly bar the therapeutic approach taken by the clinic, wrongly equating it to the notorious “conversion” therapy that seeks to turn gay people straight. © Copyright 2015 The Globe and Mail Inc.
by Jessica Hamzelou GOO, bah, waahhhh! Crying is an obvious sign something is up with your little darling but beyond that, their feelings are tricky to interpret – except at playtime. Trying to decipher the meaning behind the various cries, squeaks and babbles a baby utters will have consumed many a parent. Some researchers reckon babies are simply practising to learn to speak, while others think these noises have some underlying meaning. "Babies probably aren't aware of wanting to tell us something," says Jitka Lindová, an evolutionary psychologist at Charles University in Prague, Czech Republic. Instead, she says, infants are conveying their emotions. But can adults pick up on what those emotions are? Lindová and her colleagues put 333 adults to the test. First they made 20-second recordings of five- to 10-month-old babies while they were experiencing a range of emotions. For example, noises that meant a baby was experiencing pain were recorded while they received their standard vaccinations. The team also collected recordings when infants were hungry, separated from a parent, reunited, just fed, and while they were playing. The volunteers had to listen to a selection of the recordings then guess which situation each related to. The adults could almost always tell whether a baby was distressed in some way. This makes sense – a baby's survival may depend on an adult being able to tell whether a baby is unwell, in pain or in danger. © Copyright Reed Business Information Ltd.
|By Brian Bienkowski and Environmental Health News Male minnows exposed to a widely used diabetes drug ubiquitous in wastewater effluent had feminized reproductive parts and were smaller and less fertile, according to a new study. It is the first study to examine the drug metformin’s impact on fish endocrine systems and suggests that non-hormone pharmaceuticals pervasive in wastewater may cause reproductive and development problems in exposed fish. Metformin is largely used to combat insulin resistance associated with type-2 diabetes, which accounts for about 90 percent of all diagnosed U.S. adult diabetes cases. Researchers from the University of Wisconsin-Milwaukee exposed young fathead minnows to water containing levels of metformin commonly found in wastewater effluent. Eighty-four percent of 31 metformin-exposed male fish exhibited feminized reproductive organs. “Normally in females you see eggs developed in ova, in males, you see a different structure – producing tiny sperm instead of an egg structure,” said Rebecca Klaper, an associate professor at the University of Wisconsin-Milwaukee and senior author of the study. “We saw development of larger egg structures within the [male’s] testis.” © 2015 Scientific American
Keyword: Sexual Behavior
Link ID: 20867 - Posted: 04.30.2015
by Laura Sanders Here I am, fresh off of my second maternity leave ready to serve up lots of juicy fresh science about babies. And I would love to do that, if only I were sleeping more at night. With her intoxicating baby aroma, squishy face and sweet little coos, our newest little daughter is irresistible by day. Night is another story altogether. And it’s a sad one. Our tale begins and ends with her cries wrenching me from a dead sleep over and over again. Sometimes I lie in bed for a split second, deluding myself into thinking that maybe this time she’ll go back to sleep. That pause is long enough for me to notice all the ways her cries affect me: Pounding heart, sweaty hands and feet, and most importantly, a single-minded, maniacal focus on that sound. Evolution didn’t give babies many ways to communicate, but the method they have, crying, sure gets the job done. So I read with interest an April 23 study in Nature that explains one way in which baby cries sledgehammer a mother’s brain. Upon hearing a lost pup’s cries, mother mice promptly go and fetch the wayward pup by the scruff of its neck. But this behavior has to be learned — a first-time mom isn’t as attuned to the sounds of her pups’ cries. As she gets the hang of that whole mothering thing, the momma mouse’s brain gets better at picking the sound of a distant crying pup out of the background din. These pup cries bore their way into the mother’s brain in an interesting way, the researchers found. © Society for Science & the Public 2000 - 2015.
By Linda Carroll Women may have a harder time recovering from concussion, a new study suggests. Taiwanese researchers found women were more likely than men to continue to have memory deficits nearly three months after a mild traumatic brain injury, or mTBI, according to the study published in the journal Radiology. The findings provide "evidence that women may have greater risk for developing working memory impairment after mTBI and may have longer recovery time," said study coauthor Dr. Chi-Jen Chen, a professor at Taipei Medical University Shuang-Ho Hospital. "According to our preliminary results, more aggressive management should be initiated once mTBI is diagnosed in women, including close monitoring of symptoms, more aggressive pharmacological treatments, rehabilitation, as well as longer follow-up." Chen had noticed that almost twice as many women as men were showing up in her clinic after concussions. She wondered if there might be some kind of physical difference making concussions more severe in women. To determine whether there was a real effect, she and her colleagues rounded up 30 concussed patients and 30 non-brain-injured volunteers. Each group had equal numbers of men and women. The concussed patients were scanned shortly after doing a memory test with functional MRI twice: one month after their injury and again six weeks later. The volunteers were scanned once. All the study participants took neuropsychological tests designed to measure attention span, impulsivity, and deficits in working memory.
Mothers may influence the mood and behaviour of their babies through their breast milk, researchers say. There's growing evidence that mother's milk doesn't just affect the growth of a baby's body "but also areas of their brain that shape their motivations, their emotions, and therefore their behavioural activity," says Katie Hinde, an assistant professor of human evolutionary biology at Harvard University. In a paper published in the journal Evolution, Medicine and Public Health, Hinde and two other researchers propose a way in which the composition of breast milk could influence a baby's brain and behaviour. If food is scarce or there are a lot of predators around, it may be better for a mother to have a baby that is calmer and focuses on growing rather than one that is very active and playful, Hinde told CBC Radio's Quirks & Quarks in an interview that airs Saturday. It may be possible to influence a baby's activity level by changing the composition of the milk to affect the bacteria in the infant's gut, she added. Breast milk contains a lot of sugars that infants can't digest, but that feed bacteria that live in human intestines. Those bacteria don't just help digest food, said Hinde. "They can release chemical signals that travel to the infant's brain and shape neurodevelopment." ©2015 CBC/Radio-Canada
By Virginia Morell Like many newborn mammals, baby mice cry to get their mother’s attention. But the mother doesn’t instinctively recognize these calls; she must learn the sounds of her offspring—just as human parents must learn the cries of their infants. Now, a team of researchers has discovered that the hormone oxytocin, which has been tied to trust and maternal bonding, holds the key to how this learning occurs. Only after oxytocin tweaks the brain of a female mouse does she respond with a mother’s concern and attentiveness to crying pups. “It’s an exciting study with implications that … could be helpful to certain disorders, such as autism,” says Larry Young, a neuroscientist at Emory University in Atlanta who was not involved in the work. To understand the role oxytocin plays in a mother mouse’s brain, scientists at New York University School of Medicine first investigated how female mice in general respond to the distress calls of baby mice. Pups emit ultrasonic cries when they are separated from the nest, which sometimes happens when a mother carries her babies to a new location. (Moms change nest locations regularly to elude predators.) When a mother hears these cries, she runs to the lost pup, picks it up, and carries it back to her nest. Other scientists have shown that moms respond even to the distress cries of pups that aren’t their own, readily approaching loudspeakers that broadcast the calls. Most virgin female mice, though, couldn’t care less; they seem completely indifferent to the pups’ cries for help. And yet, some virgin females that have either been housed with a mother and her litter or have been injected with oxytocin will retrieve crying infants. © 2015 American Association for the Advancement of Science.
By JAMES GORMAN Studies of hunters and gatherers — and of chimpanzees, which are often used as stand-ins for human ancestors — have cast bigger, faster and more powerful males in the hunter role. Now, a 10-year study of chimpanzees in Senegal shows females playing an unexpectedly big role in hunting and males, surprisingly, letting smaller and weaker hunters keep their prey. The results do not overturn the idea of dominant male hunters, said Jill D. Pruetz of Iowa State University, who led the study. But they may offer a new frame of reference on hunting, tools and human evolution. “We need to broaden our perspective,” she said. Among the 30 or so chimps Dr. Pruetz and her colleagues observed, called the Fongoli band, males caught 70 percent of the prey, mostly by chasing and running it down. But these chimps are very unusual in one respect. They are the only apes that regularly hunt other animals with tools — broken tree branches. And females do the majority of that hunting for small primates called bush babies. Craig Stanford, an anthropologist at the University of Southern California who has written extensively on chimp hunting and human evolution, said the research was “really important” because it solidified the evidence for chimps hunting with tools, which Dr. Pruetz had reported in earlier papers. It also clearly shows “the females are more involved than in other places,” he said, adding that it provides new evidence to already documented observations that female chimps are “much more avid tool users than males are.” All chimpanzees eat a variety of plant and animal foods, including insects like termites. And all chimpanzees eat some other animals. The most familiar examples of chimpanzee hunting are bands of the apes chasing red colobus monkeys through the trees in the rain forests of East Africa. © 2015 The New York Times Company
Boer Deng Universities in the United States employ many more male scientists than female ones. Men are paid more, and in fields such as mathematics, engineering and economics, they hold the majority of top-level jobs. But in a sign of progress, a 13 April study finds that faculty members prefer female candidates for tenure-track jobs in science and engineering — by a ratio of two to one. That result, based on experiments involving hypothetical job seekers, held true regardless of the hirer’s gender, department, career status or university type, researchers report in the Proceedings of the National Academy of Sciences1. “We were shocked,” says Wendy Williams, a psychologist at Cornell University in Ithaca, New York, and a co-author of the study. With fellow Cornell psychologist Stephen Ceci, she surveyed 873 tenure-track faculty members in biology, psychology, economics and engineering at 371 US universities. One experiment presented participants with three hypothetical job candidates, of which two were identical except for their gender. Another experiment added descriptions of marital and parental status, to test whether underlying assumptions about gender choices affected hiring. “You don’t frequently see that level of attention and sophistication” in statistical analysis, says Robert Santos, vice-president of the American Statistical Association in Alexandria, Virginia. Nothing seemed to sway study participants’ preference for female job candidates. The authors say that this is interesting given their previous finding that a relatively low percentage of female PhDs in the social and biological sciences secure academic positions — in part because they are less likely than men to apply for these jobs. Other research suggests that in the physical sciences, women and men are just as likely to secure a tenure-track position within five years of earning a PhD. © 2015 Nature Publishing Group
Keyword: Sexual Behavior
Link ID: 20792 - Posted: 04.14.2015
by Bethany Brookshire In 2011, a group of scientists “turned mice gay.” The only issue is, of course, they didn’t. Rather, Yi Rao and colleagues at Peking University in Beijing, China, showed that male mice will cheerfully mount both male and female mice, as long as their brains are deficient in one chemical messenger: serotonin. The paper, published in Nature, received plenty of media coverage. Now, two other research groups report seemingly opposite findings: Male mice with no serotonin in their brains still prefer female mice to males. The researchers contend that serotonin is about social communication and impulsive behaviors, not sex. Mounting behavior aside, sexual preference in mice is not about “turning mice gay.” It never has been. Instead, it’s about the role that a single chemical can play in animal behavior. And it’s about what, exactly, those behaviors really mean. Serotonin serves as a messenger between cells. It plays important roles in mood. Serotonin-related drugs are used to treat some forms of migraine. And of course, serotonin plays a role in the psychedelic effects of recreational drugs such as hallucinogens. So when the Peking University group set out to show serotonin’s role in sexual preference, they attacked it from several angles. They used mice that had been genetically engineered to lack the brain cells that usually produce serotonin. They used a chemical to deplete serotonin in the brains of normal mice. And they created another strain of mice that lacked the enzyme that makes serotonin in the brain. © Society for Science & the Public 2000 - 2015
Keyword: Sexual Behavior
Link ID: 20787 - Posted: 04.11.2015
By Emily Underwood A splashy headline appeared on the websites of many U.K. newspapers this morning, claiming that men whose brothers or fathers have been convicted of a sex offense are “five times more likely to commit sex crimes than the average male” and that this increased risk of committing rape or molesting a child “may run in a family’s male genes.” The study, published online today in the International Journal of Epidemiology, analyzed data from 21,566 male sex offenders convicted in Sweden between 1973 and 2009 and concluded that genetics may account for at least 40% of the likelihood of committing a sex crime. (Women, who commit less than 1% of Sweden’s sexual offenses, were omitted from the analysis.) The scientists have suggested that the new research could be used to help identify potential offenders and target high-risk families for early intervention efforts. But independent experts—and even the researchers who led the work, to a certain degree—warn that the study has some serious limitations. Here are a few reasons to take its conclusions, and the headlines, with a generous dash of salt. Alternate explanations: Most studies point to early life experiences, such as childhood abuse, as the most important risk factor for becoming a perpetrator of abuse in adulthood. The new study, however, did not include any detail about the convicted sex criminals’ early life exposure to abuse. Instead, by comparing fathers with sons, and full brothers and half-brothers reared together or apart, the scientists attempted to tease out the relative contributions of shared environment and shared genes to the risk of sexual offending. Based on their analyses, the researchers concluded that shared environment accounted for just 2% of the risk of sexual offense, while genetics accounted for roughly 40%. Although there is likely some genetic contribution to sexual offending—perhaps related to impulsivity or sex drive—the group “may be overestimating the role of genes” because their assumptions were inaccurate, says Fred Berlin, a psychiatrist and sexologist at Johns Hopkins University in Baltimore, Maryland. © 2015 American Association for the Advancement of Science.
Drawing on the widest survey of sexual behaviour since the Kinsey Report, David Spiegelhalter, in his book Sex By Numbers, answers key questions about our private lives. Here he reveals how Kinsey’s contested claim that 10% of us are gay is actually close to the mark For a single statistic to be the primary propaganda weapon for a radical political movement is unusual. Back in 1977, the US National Gay Task Force (NGTF) was invited into the White House to meet President Jimmy Carter’s representatives – a first for gay and lesbian groups. The NGTF’s most prominent campaigning slogan was “we are everywhere”, backed up by the memorable statistical claim that one in 10 of the US population was gay – this figure was deeply and passionately contested. So where did Bruce Voeller, a scientist who was a founder and first director of the NGTF, get this nice round 10% from? To find out, we have to delve back into Alfred Kinsey’s surveys in 1940s America, which were groundbreaking at the time but are now seen as archaic in their methods: he sought out respondents in prisons and the gay underworld, made friends with them and, over a cigarette, noted down their behaviours using an obscure code. Kinsey did not believe that sexual identity was fixed and simply categorised, and perhaps his most lasting contribution was his scale, still used today, in which individuals are rated from exclusively heterosexual to exclusively homosexual on a scale of 0 to 6. Kinsey’s headline finding was that “at least 37% of the male population has some homosexual experience between the beginning of adolescence and old age”, meaning physical contact to the point of orgasm. © 2015 Guardian News and Media Limited
Keyword: Sexual Behavior
Link ID: 20760 - Posted: 04.06.2015
by Alison George Misguided notions about our sexual appetites are missing the bigger picture and making people unhappy, says Emily Nagoski Why is there no such thing as a sex drive? A drive is a motivational system to deal with life-or-death issues, like hunger or being too cold. You're not going to die if you don't have sex. But biologists might say that if you don't reproduce, that is a form of death Yes. That's the argument that was used when desire was being added to the way sexual dysfunctions were diagnosed in the 1970s, to justify the framing of sexual desire as a drive. But when it comes to sex, there just isn't any physical evidence of a drive mechanism. So what's going on? If sex is a drive then desire should be spontaneous, like a hunger. When you see a sexy person or have a stray sexy thought, it activates an internal craving or urge for sex. That's called "spontaneous desire". It feels like it comes out of the blue. But there is another way of experiencing desire which is also healthy and normal, called "responsive desire", where your interest only emerges in response to arousal. So, your partner comes over and starts kissing your neck and you're like, "oh, right, sex, that's a good idea". Do you think an absence of spontaneous desire is normal? Yes. If our metaphor for desire is hunger, if you are never hungry for food there will be dire consequences and that's clearly a disorder, right? That's a medical problem that needs to be fixed. But not experiencing spontaneous hunger for sex doesn't have dire consequences; it is not a medical disorder. I think the reason we expect everyone to have spontaneous desire is because that's how most men experience it. © Copyright Reed Business Information Ltd
Keyword: Sexual Behavior
Link ID: 20759 - Posted: 04.06.2015
Hannah Devlin, science correspondent They may stop short of singing The Bells of Saint Mary’s, as demonstrated by the mouse organ in Monty Python, but scientists have discovered that male mice woo females with ultrasonic songs. The study shows for the first time that mouse song varies depending on the context and that male mice have a specific style of vocalisation reserved for when they smell a female in the vicinity. In turn, females appear to be more interested in this specific style of serenade than other types of squeak that male mice produce. “It was surprising to me how much change occurs to these songs in different social contexts, when the songs are thought to be innate,” said Erich Jarvis, who led the work at Duke University in North Carolina. “It is clear that the mouse’s ability to vocalise is a lot more limited than a songbird’s or human’s, and yet it’s remarkable that we can find these differences in song complexity.” The findings place mice in an elite group of animal vocalisers, that was once thought to be limited to birds, whales, and some primates. Mouse song is too high-pitched for the human ear to detect, but when listened to at a lower frequency, it sounds somewhere between birdsong and the noise of clean glass being scrubbed. The Duke University team recorded the male mice when they were roaming around their cages, when they were exposed to the smell of female urine and when they were placed in the presence of a female mouse. They found that males sing louder and more complex songs when they smell a female but don’t see her. By comparison, the songs were longer and simpler when they were directly addressing their potential mate, according to the findings published in Frontiers of Behavioural Neuroscience. © 2015 Guardian News and Media Limited
Sara Reardon A new study finds that children's cognitive skills are linked to family income. The stress of growing up poor can hurt a child’s brain development starting before birth, research suggests — and even very small differences in income can have major effects on the brain. Researchers have long suspected that children’s behaviour and cognitive abilities are linked to their socioeconomic status, particularly for those who are very poor. The reasons have never been clear, although stressful home environments, poor nutrition, exposure to industrial chemicals such as lead and lack of access to good education are often cited as possible factors. In the largest study of its kind, published on 30 March in Nature Neuroscience1, a team led by neuroscientists Kimberly Noble from Columbia University in New York City and Elizabeth Sowell from Children's Hospital Los Angeles, California, looked into the biological underpinnings of these effects. They imaged the brains of 1,099 children, adolescents and young adults in several US cities. Because people with lower incomes in the United States are more likely to be from minority ethnic groups, the team mapped each child’s genetic ancestry and then adjusted the calculations so that the effects of poverty would not be skewed by the small differences in brain structure between ethnic groups. The brains of children from the lowest income bracket — less than US$25,000 — had up to 6% less surface area than did those of children from families making more than US$150,000, the researchers found. In children from the poorest families, income disparities of a few thousand dollars were associated with major differences in brain structure, particularly in areas associated with language and decision-making skills. Children's scores on tests measuring cognitive skills, such as reading and memory ability, also declined with parental income. © 2015 Nature Publishing Group,