By Nathan Seppa A nutritional supplement that is free of charge, offers a wide range of health benefits and poses little risk sounds like fodder for a late-night TV commercial. But proponents of vitamin D are increasingly convinced that the sunshine vitamin delivers the goods, no strings attached. It offers a safe route to better health, these advocates say, by promoting proper function of the bones, heart, brain, immune system, you name it. Yet, the proponents claim, most people don’t get enough. Whereas humans’ pre­historic ancestors lived outdoors and made oodles of vitamin D in their sun-exposed skin, people today have become shut-ins by comparison — and scant sun exposure means low vitamin D. Of course, not everyone sees such a grand reach for the vitamin. While scientists concur that it is essential for bone maintenance, some stop right there. The skeptics note that vitamin D’s other promising qualities have shown up largely in studies that fall short of the gold standard of medicine — the randomized controlled trial, in which groups of people get either a placebo or the real thing. While a handful of randomized trials have shown additional benefits, others have not, leaving a gap in the vitamin’s otherwise sterling reputation. This debate came to a head last November, when an Institute of Medicine panel of scientists announced new vitamin D recommendations. The old intake levels were barely high enough to prevent rickets, a bone condition associated with the Industrial Revolution. The IOM panel boosted the recommended daily intake of the vitamin from 200 to 600 international units per day for most of the population. The new dose is about 15 micrograms, in the range of vitamin D found in most multivitamins. © Society for Science & the Public 2000 - 2011

Keyword: Parkinsons; Aggression
Link ID: 15531 - Posted: 07.05.2011

By Janet Raloff An ingredient in many clear plastics also renders some gender-linked behaviors plastic, at least in mice. Two new studies link feminized behaviors in adult males with exposures during development to bisphenol A, a weak estrogen-mimicking chemical. In one study, some behaviors in BPA-exposed females morphed into features characteristic of males. The findings come from laboratory studies conducted in different species. Each experiment also exposed animals at a different time during development — one from the womb through weaning, the other during the rodent equivalent of adolescence and early adulthood. The trials therefore identify different periods during which the brain appears vulnerable to pollutants that mimic or alter the activity of sex hormones. Because early BPA exposures left no lasting changes in sex hormone levels, the authors of each study note, the behavioral changes they observed in adulthood probably trace to an earlier rewiring of brain circuitry — most likely in an area known as the hippocampus. Cheryl Rosenfeld of the University of Missouri–Columbia and her colleagues added BPA to the chow they fed to pregnant deer mice. BPA concentrations in the moms peaked at around 9 nanograms per milliliter, Rosenfeld says, “which is in the range of what’s been measured in humans.” © Society for Science & the Public 2000 - 2011

Keyword: Sexual Behavior; Aggression
Link ID: 15516 - Posted: 06.30.2011

by Elizabeth Norton Life for those with a genetic disease called Prader-Willi syndrome, which affects an estimated one out of 15,000 people, can be challenging both for the patient and his or her family. Sufferers have an insatiable hunger that can lead to life-threatening obesity if access to food is not restricted. And worse, they have behavioral problems akin to autism. Tantrums and tears are common because these patients have difficulty understanding the motives of others and controlling their own emotions. But treatment with the brain hormone oxytocin may help bring both emotions and eating into balance, according to a new study. Several clues pointed to the potential of oxytocin, often thought of as the "trust hormone." Research conducted on the brain tissue donated after death from Prader-Willi patients showed that the hypothalamus (the body's thermostat) has abnormalities in the nerve cells that produce this hormone. Moreover, the hypothalamus releases oxytocin in response to touching, social interactions, relaxation, and trust—all the things people with Prader-Willi syndrome have trouble with. And oxytocin treatments have improved the social skills of autistic patients. Finally, the hormone is thought to contribute to feelings of fullness after eating, "satiety" in scientific parlance. To see whether oxytocin could benefit individuals with Prader-Willi syndrome, endocrinologist Maïthé Tauber of the Children's Hospital in Toulouse, France, and colleagues injected oxytocin or a placebo into the noses of 24 adult patients. The researchers monitored the patients' behavior; they also used cartoon stories to test patients' grasp of social interactions and pictures of faces to see how well they could recognize emotions. © 2010 American Association for the Advancement of Science

Keyword: Hormones & Behavior; Aggression
Link ID: 15485 - Posted: 06.25.2011

By KATHRYN HARRISON Readers who can’t identify Jean-Martin Charcot as the name of the French neurologist whose 19th-century experiments with hypnosis influenced Sigmund Freud’s theory of neurosis may yet recognize the work he conducted at the Saltpêtrière Hospital in Paris. Photographs and illustrations of Charcot’s patients, all women suffering hysteria, remain in currency today, 140 years after they were made, if more as curiosities than as clinically valuable documents. Once seen, these images — of, for example, a woman wearing little more than a tangle of bed sheets, her eyes rolled up into her head in either “ecstasy” or “delirium,” or fixed on the invisible object of her “amorous supplication” — are not easily forgotten, let alone dismissed. Poses classified as “passionate attitudes,” they have the disquieting aspect of pornography masquerading as intellectual inquiry. Charcot, as portrayed in Asti Hust­vedt’s consistently enthralling “Medical Muses,” focused intently — myopically, one could argue — on using hypnosis to induce hysteria and make “his hysterics, with their bizarre fits and spasms, into ideal medical specimens.” But the provocative behavior of those “specimens” transformed Saltpêtrière into something closer to a carnival than a teaching hospital. As much showman as physician, Charcot gave weekly two-hour lectures to a packed amphitheater, including demonstrations designed to captivate an audience accustomed to staged séances and exhibitions of mesmerism or telepathy. One of Charcot’s students described the dramatic potential of exhibiting hypnotized women: “We can cut them, prick them and burn them, and they feel nothing.” © 2011 The New York Times Company

Keyword: Hormones & Behavior
Link ID: 15460 - Posted: 06.20.2011

FOR people worried about the feminising effect of oestrogen-like chemicals in the water there is now a modern-day equivalent of the canary in the coal mine: a genetically modified fish in a bowl. Male fish exposed to oestrogen have delayed sperm development and grow smaller testes. Some industrial chemicals, such as bisphenol A, mimic oestrogen, but little is known about how the effects of different oestrogen-like chemicals add up in water. To find out, Xueping Chen and colleagues at Vitargent, a biotechnology company in Hong Kong, have created a genetically engineered fish that glows green when it is exposed to oestrogen-like chemicals. Chen's team took the green fluorescent protein gene from jellyfish and spliced it into the genome of the medaka fish, Oryzias melastigma, next to a gene that detects oestrogen. Chemicals that have oestrogen-like activity cause the fish to express the modified gene, making them glow. When the team tested the fish at eight sites around Hong Kong, they found that some chemicals that showed weak or no oestrogenic activity, including UV filters used in sunscreen, had combined in water to amplify or create an oestrogenic effect. The work is as yet unpublished. William Price of the University of Wollongong in New South Wales, Australia, warns the approach does not detect a biological response. © Copyright Reed Business Information Ltd.

Keyword: Hormones & Behavior; Aggression
Link ID: 15415 - Posted: 06.11.2011

By Tina Hesman Saey Women with lower levels of the hormone oxytocin in their blood during late stages of pregnancy are more likely to develop postpartum depression, new research suggests. The finding, published online May 11 in Neuropsychopharmacology, may be a first step toward identifying pregnant women who are at risk of becoming depressed after the birth of their babies. While the link is intriguing, “there’s a lot of steps to go between a correlation and using it as a biomarker,” says Ziad Nahas, a psychiatrist and mood disorders researcher at the Medical University of South Carolina in Charleston who was not involved in the study. Oxytocin helps stimulate contractions and lactation in pregnant women. The hormone has also been implicated in facilitating emotional bonds between people, including mothers and children. Some earlier studies have linked oxytocin to depression, but not to postpartum depression. Of 73 women who volunteered blood samples for the study, 14 later developed postpartum depression. Oxytocin concentrations in the women’s blood varied widely, from 14.4 to 245.7 picograms per milliliter. Although the researchers found a great deal of overlap in oxytocin levels between the two groups, women who got depressed tended to have lower levels. The link is too preliminary for doctors to use oxytocin levels to predict which patients are likely to develop postpartum depression, says Gunther Meinlschmidt, a psychobiologist at the University of Basel in Switzerland who led the study. Even if a woman has low levels of the hormone, there’s no guarantee she will get depressed. “This is not a yes, no, one-or-zero factor. It’s one of several factors” that determine a woman’s risk for the condition, he says. It’s also unclear whether treating women with oxytocin would have any effect on depression. © Society for Science & the Public 2000 - 2011

Keyword: Depression; Aggression
Link ID: 15320 - Posted: 05.12.2011

By LISA SANDERS, M.D. A fiercely independent and active 76-year-old woman spent the past decade caring for her aged mother, who died at 99. Weeks after her mother’s death, the woman collapsed at home. She was found to have bleeding from a collection of abnormal blood vessels (known as AVMs, or arteriovenous malformations) in her colon. In the months after, the patient’s red-blood-cell count returned to normal, but she never regained her old energy and strength. She told her daughters that she was weaker and more tired than she had ever been in her life. Dr. Susan Wiskowski, a family physician in Hartford, was the woman’s doctor. Until recently, the patient was in good health for her age, with only a few medical problems: high blood pressure, which was controlled with one medication; hypothyroidism, treated with Synthroid; and cataracts, which had been surgically repaired. Now, out of the blue, she was experiencing rapid weight gain, swelling and weakness in her legs, which made it hard to walk. A couple of weeks after the cardiac work-up, the patient’s behavior became erratic and strange. Despite her complaints of weakness, she veered between bursts of activity — endlessly cleaning her house, giving large dinner parties — and days of isolation and fatigue. She was sometimes elated, telling her four daughters that she’d found where heaven was located. She began to talk about giving away her possessions. One afternoon she seemed completely out of control. A neighbor called 911, and the patient was rushed by ambulance to St. Francis Hospital in Hartford. © 2011 The New York Times Company

Keyword: Hormones & Behavior
Link ID: 15297 - Posted: 05.07.2011

Joanna Marchant Female athletes may not be eligible to compete as women if they have natural testosterone levels in the male range. That's the upshot of new guidelines on female hyperandrogenism, recommended by the International Olympic Commission (IOC) on 5 April and accepted by the International Association of Athletics Federations (IAAF) on 12 April. The rules have been welcomed by experts as a reasonable compromise, but there remain some doubts over how they would work in practice. Nature looks at the science behind the tests. The regulations cover female athletes with hyperandrogenism, a condition in which the body produces higher than normal levels of hormones called androgens, particularly testosterone. This can cause the development of bulky muscles, perhaps giving athletes an unfair competitive advantage. The issue hit the headlines in 2009, when the South African athlete Caster Semenya was asked to undergo sex testing after winning the 800-metre final at the Berlin World Championships in Athletics (see 'A question of sex'). She was unable to compete for nearly a year, but has now returned to the track. The results of her tests remain confidential. Officials deny that the new rules are a direct response to Semenya's case, however. There have been other controversial cases, and they say there has long been a need to clarify the rules and procedures involved. This week's announcement is the culmination of an 18-month review carried out by the IOC Medical Commission and the IAAF, including a meeting held last October and attended by scientists as well as athletes, bioethicists, human-rights lawyers and a representative of the intersex community. © 2011 Nature Publishing Group,

Keyword: Sexual Behavior; Aggression
Link ID: 15219 - Posted: 04.16.2011

By Amina Zafar, CBC News The role estrogen plays in women's brains remains murky but researchers are beginning to clarify it. The first Women's Brain Health Academic Symposium in Toronto on Wednesday brought together experts from North America leading a discussion about trying to better understand the female brain. "Seventy per cent of Alzheimer's patients are women," said Lynn Posluns, founder and chair of the Women of Baycrest, which aims to raise $5 million for a research chair devoted to women's brain health. Researchers want to uncover exactly how estrogen affects different regions of the female brain.Researchers want to uncover exactly how estrogen affects different regions of the female brain. Brian Snyder/Reuters Yet most laboratory studies today are done on male rats because female rats are considered too complex, Posluns said. "I'm saying there's a real disconnect here. It is time for scientists to better understand the female brain." At the symposium, Gillian Einstein, a professor of psychology and public health at the University of Toronto, talked about her early findings exploring the role of estrogen on brain functions such as mood and memory. "I want women to be circumspect about the effect of their hormones on their mood and cognition," said Einstein. "It may or may not be PMS that makes you grumpy. It's possible that your husband really did do something crappy, and you have a reasonable response to it. [On the other hand] I also think it's important to think they may be having an effect." © CBC 2011

Keyword: Hormones & Behavior; Aggression
Link ID: 15191 - Posted: 04.07.2011

by Jessica Hamzelou BASEBALL star Barry Bonds is back in the spotlight this week, for all the wrong reasons. The sports legend is on trial in the US, accused of lying to a grand jury when he denied that he had ever knowingly taken performance-enhancing steroids. Meanwhile, psychologists are beginning to work out how these drugs can trigger aggressive behaviour and suggesting potential therapies that could be taken alongside steroids to block this unwelcome side effect. But could such a therapy encourage drug abuse? At the end of 2007, Bonds was charged with making false statements and obstruction of justice. He pleaded not guilty and his trial commenced on 21 March this year. In support of the case that Bonds took steroids, his ex-girlfriend, Kimberly Bell, gave evidence in which she claimed that he exhibited periods of aggressive behaviour. Aggression is one of the better-known side effects of steroid use and is often referred to as "roid rage". A survey in 2008 of 7000 American teenage boys found those who took anabolic steroids reported significantly higher levels of violent behaviour than boys who did not take them (American Journal of Public Health, DOI: 10.2105/ajph.2008.137018). Now, Thomas Hildebrandt's team at Mount Sinai School of Medicine in New York are conducting the first longitudinal study of anabolic steroid users. By monitoring participants before, during and after cycles of steroid use, the group hopes to work out how the drugs exert their effects and how long these might last. © Copyright Reed Business Information Ltd.

Keyword: Aggression; Aggression
Link ID: 15185 - Posted: 04.07.2011

by Sara Reardon If you want to know whether your new fluffy puppy will be a cuddly friend or snarl at and bite anything that moves, you might want to check out the length of its genes. Researchers at the University of Tokyo in Japan asked 100 Akita owners to fill out questionnaires about whether their pooches were naughty or nice. When they looked at the doggies' DNA, the scientists found that the meanest males more often had a shortened gene for a receptor that responds to various male hormones. The gene variant produces a form of the protein that has previously been shown to respond more strongly to testosterone. This is the first time that canine aggression has been associated with genetic differences in the male hormone receptor, the researchers report in Biology Letters this week. Over half of the Akitas they studied had this variant. Yet mean female dogs weren't more likely to have the short variant than the gentle dogs, suggesting that females respond differently to these hormones. © 2010 American Association for the Advancement of Science.

Keyword: Aggression; Aggression
Link ID: 15156 - Posted: 03.31.2011

by Rebecca Kessler Fear of heights can drive people to extremes, from crossing the country by bus to avoid flying to commuting extra hours every week to circumvent a high bridge. A new study now suggests one counterintuitive path to relief: The human stress hormone cortisol seems to improve the effectiveness of behavioral therapy to help people overcome their fear of heights. The standard treatment for many phobias involves exposing someone to the source of their fear in a safe environment—either in real life or, increasingly, using virtual reality. When nothing bad happens, that person gradually learns that the source—whether it's heights, snakes, or enclosed spaces—is safe. In a process called "extinction," new memories of safe experiences prevail over ingrained memories of scary ones. The treatment works, but it can take many repetitions to stick and is unpleasant enough that some patients drop out. So researchers have been looking for drugs that might be used in combination with extinction-based therapy and can help speed it up. One drug called D-cycloserine, which helps new memories form, is being tested in clinical trials in people with certain phobias. But human and animal studies have shown that hormones released during stressful situations go one step further, not only promoting the creation of new "safe" memories but also inhibiting fear memories, says cognitive neuroscientist Dominique de Quervain of the University of Basel in Switzerland, who lead the present study, published today in the Proceedings of the National Academy of Sciences. © 2010 American Association for the Advancement of Science.

Keyword: Emotions; Aggression
Link ID: 15143 - Posted: 03.29.2011

CONJURE up an image of a financial risk-taker, and you'll probably picture an aggressive Wall Street trader, testosterone surging as he closes the deal. But new research suggests that people with low levels of the male sex hormone are also likely to take financial risks. Previous studies have linked high levels of testosterone to certain risk-seeking behaviours. To investigate whether financial risk-taking follows a similar pattern, Scott Huettel at Duke University in Durham, North Carolina, measured the testosterone levels of 298 people, who then took part in trials in which they chose between a fixed known reward or a gamble between getting a payout - mostly larger than the fixed reward - or nothing. Overall, the volunteers generally preferred the known return than the gamble, even if they would have been better off, on average, by taking a chance. Surprisingly, the biggest risks were taken by people with very high or very low testosterone, compared with the average levels for their gender (Psychological Science, DOI: 10.1177/0956797611401752). Economists want to predict who is likely to be successful at playing financial markets, says Dario Mastripieri at the University of Chicago. "It's legitimate to ask if biology is going to have an effect." © Copyright Reed Business Information Ltd.

Keyword: Hormones & Behavior; Aggression
Link ID: 15118 - Posted: 03.21.2011

Ewen Callaway A sperm's path to an egg is more a deadly obstacle course than a track sprint. The one ejaculated sperm cell in a million that is lucky enough to reach the fallopian tubes, where eggs await fertilization, must conquer thick, gelatinous layers of mucus and cells surrounding the egg to reach its prize. Fortunately for the sperm, there is help. Two studies published today in Nature1,2 show how sperm sense progesterone, a female sex hormone, that has been released by cells surrounding the egg. The hormone may guide the sperm towards the egg as well as giving it a final push to get there, the research suggests. The findings could be used to design a new class of contraceptive drug. "It really is a significant step forward in terms of how we understand what regulates sperm," says Steven Publicover, a reproductive biologist at the University of Birmingham, UK, who was not involved in either study. In some previous experiments, ejaculated human sperm have been shown to swim towards areas with high levels of progesterone. The hormone also causes the cells to beat their whip-like tails more powerfully to make it through to the egg, a condition called hyperactivity. "We've got good reason to think that the response to progesterone matters, but it's bloody difficult to pin it down," says Publicover. Changing channel The latest studies, led by independent teams in Germany and the United States who agreed to publish their findings simultaneously, show that progesterone activates a molecular channel called CatSper, which floods sperm cells with calcium. © 2011 Nature Publishing Group

Keyword: Sexual Behavior; Aggression
Link ID: 15111 - Posted: 03.17.2011

by Greg Miller Only a small minority of people who fall victim to a violent attack or witness a bloody accident suffer the recurring nightmares, hypervigilance, and other symptoms of posttraumatic stress disorder (PTSD). Women seem to be twice as susceptible as men, but otherwise researchers know virtually nothing about who is most at risk or why. Now a study has linked a genetic mutation and blood levels of a particular peptide—a compound made from a short string of the same building blocks that make up proteins—to the severity of PTSD symptoms in women. The finding could lead to tests to identify people who may need extra help after a traumatic event. In the new study, researchers led by Kerry Ressler, a psychiatrist and molecular neurobiologist at Emory University in Atlanta, focused on a peptide thought to play a role in cells' response to stress: pituitary adenylate cyclase-activating polypeptide (PACAP). The team measured levels of PACAP in the blood of 64 patients who volunteered for their study at Grady Memorial Hospital in Atlanta. The vast majority of volunteers were from poor neighborhoods in the city, and Ressler says more than 90% reported having witnessed or suffered from a traumatic event such as gun violence or physical or sexual assault in the past. The researchers found a correlation between PACAP levels and scores on a standard scale of PTSD symptoms in women—but no such correlation in men. In a second group of 74 women, the researchers found a similar correlation between PACAP levels and symptom severity. Ressler estimates that with all else being equal, women with high PACAP levels are up to five times as likely as women with low levels to have symptoms severe enough to meet the diagnostic criteria for PTSD. © 2010 American Association for the Advancement of Science.

Keyword: Stress; Aggression
Link ID: 15044 - Posted: 02.24.2011

by Wendy Zukerman Is it that time of the month? These are the words no man should ever utter. How about this for a diplomatic alternative: "Are your GABA receptors playing up?" You may be spot on. It seems that these brain cells are to blame for some women's monthly mood swings. Many women feel a little irritable before menstruating, but up to 8 per cent suffer extreme symptoms, including anxiety, depression and fatigue. Symptoms of what's called premenstrual dysphoric disorder (PMDD) begin around a week before menstruation when women are in the "late luteal phase" of their cycle and progesterone levels are at their height. Symptoms quickly subside after menstruation, once the so-called "follicular phase" has kicked in. To investigate potential mechanisms behind PMDD, Andrea Rapkin at the University of California, Los Angeles used a PET scan, which shows where glucose is being metabolised to identify activity in the brain. The idea was to analyse the brain activity of 12 women with PMDD and 12 without the condition, at various times throughout their menstrual cycle. Before each scan, the women rated the severity of any symptoms they had on a scale of one to six. Blood samples were also taken to test their hormone levels. Fluctuating hormones were not to blame: all the women experienced similar jumps in progesterone levels throughout their cycle, irrespective of whether they had PMDD or not. © Copyright Reed Business Information Ltd.

Keyword: Hormones & Behavior; Aggression
Link ID: 15002 - Posted: 02.15.2011

By Bruce Bower SAN ANTONIO — Oxytocin, a hormone with a rosy reputation for getting people to love, trust and generally make nice with one another, can get down and dirty, according to evidence presented on January 28 at the annual meeting of the Society for Personality and Social Psychology. This brain-altering substance apparently amplifies whatever social proclivities a person already possesses, whether positive or negative, says psychologist Jennifer Bartz of Mount Sinai School of Medicine in New York City. Previous work has shown that a nasal blast of the hormone encourages a usually trusting person to become more trusting (SN Online: 5/21/08), but now Bartz and her colleagues find that it also makes a highly suspicious person more uncooperative and hostile than ever. “Oxytocin does not simply make everyone feel more secure, trusting and prosocial,” Bartz says. These new results raise concerns about plans by some researchers to administer oxytocin to people with autism and other psychiatric conditions that include social difficulties, she adds. Her team studied 14 people diagnosed with borderline personality disorder and 13 volunteers with no psychiatric conditions. Symptoms of borderline personality disorder include severe insecurity about relationships, fears of abandonment and constant, needy reassurance-seeking from partners. © Society for Science & the Public 2000 - 2011

Keyword: Hormones & Behavior; Aggression
Link ID: 14942 - Posted: 02.01.2011

By NICHOLAS BAKALAR A new study suggests that a widely prescribed antidepressant may provide at least some relief for women with hot flashes. Hormone replacement therapy is now the only treatment approved by the Food and Drug Administration for menopausal symptoms, but many believe its risks outweigh its benefits. This study, published Thursday in The Journal of the American Medical Association, was a randomized, double-blinded, placebo-controlled trial of escitalopram (brand name Lexapro) in which 97 menopausal women took the drug for eight weeks while a matched group took a placebo. Just over half of the women in the treatment group reported a decrease of at least 50 percent in the frequency of hot flashes; 36 percent did in the placebo group. Women taking escitalopram averaged 1.41 fewer hot flashes per day than in those on the placebo, and there were no serious side effects. And almost two-thirds of the treatment group wanted to continue the medication, compared with 42 percent of the others. The lead author, Ellen W. Freeman, a professor of obstetrics and gynecology at the University of Pennsylvania, stressed that this is an off-label use of the drug not approved by the F.D.A. Still, she said, “it provides an option, and there’s not much out there that has been shown to be effective.” © 2011 The New York Times Company

Keyword: Hormones & Behavior; Aggression
Link ID: 14914 - Posted: 01.25.2011

Having the lights on before bedtime could result in a worse night's sleep, according to a study to be published in the Journal of Endocrinology and Metabolism. The research shows that the body produces less of the sleep hormone melatonin when exposed to light. Sleep patterns have been linked to some types of cancer, blood pressure and diabetes. The US researchers also found lower melatonin levels in shift workers. Lifestyles may have moved on from a day/night rhythm, but it seems the human body has not. The pineal gland produces melatonin through the night and starts when darkness falls. Researchers have shown that switching on lights in the home switches off the hormone's production. In the study, 116 people spent five days in room where the amount of light and sleep was controlled. They were awake for 16 hours and asleep for eight hours each day. Initially the patients were exposed to 16 hours of room light during their waking hours. They were then moved onto eight hours of room light in the morning and eight hours of dim light in the evening. The researchers found that electrical light between dusk and bedtime strongly suppressed melatonin levels. With dim light, melatonin was produced for 90 minutes more a day. BBC © MMXI

Keyword: Biological Rhythms; Aggression
Link ID: 14880 - Posted: 01.17.2011

By NICHOLAS WADE Oxytocin has been described as the hormone of love. This tiny chemical, released from the hypothalamus region of the brain, gives rat mothers the urge to nurse their pups, keeps male prairie voles monogamous and, even more remarkable, makes people trust each other more. Yes, you knew there had to be a catch. As oxytocin comes into sharper focus, its social radius of action turns out to have definite limits. The love and trust it promotes are not toward the world in general, just toward a person’s in-group. Oxytocin turns out to be the hormone of the clan, not of universal brotherhood. Psychologists trying to specify its role have now concluded it is the agent of ethnocentrism. A principal author of the new take on oxytocin is Carsten K. W. De Dreu, a psychologist at the University of Amsterdam. Reading the growing literature on the warm and cuddly effects of oxytocin, he decided on evolutionary principles that no one who placed unbounded trust in others could survive. Thus there must be limits on oxytocin’s ability to induce trust, he assumed, and he set out to define them. In a report published last year in Science, based on experiments in which subjects distributed money, he and colleagues showed that doses of oxytocin made people more likely to favor the in-group at the expense of an out-group. With a new set of experiments in Tuesday’s issue of the Proceedings of the National Academy of Sciences, he has extended his study to ethnic attitudes, using Muslims and Germans as the out-groups for his subjects, Dutch college students. © 2011 The New York Times Company

Keyword: Hormones & Behavior; Aggression
Link ID: 14855 - Posted: 01.11.2011