Chapter 11. Emotions, Aggression, and Stress
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By JAMES DAO Reviving a 20-year debate over illnesses of veterans of the 1991 Persian Gulf war, a new scientific paper presents evidence that nerve agents released by the bombing of Iraqi chemical weapons depots just before the ground war began could have carried downwind and fallen on American troops staged in Saudi Arabia. The paper, published in the journal Neuroepidemiology, tries to rebut the longstanding Pentagon position, supported by many scientists, that neurotoxins, particularly sarin gas, could not have carried far enough to sicken American forces. The authors are James J. Tuite and Dr. Robert Haley, who has written several papers asserting links between chemical exposures and gulf war illnesses. They assembled data from meteorological and intelligence reports to support their thesis that American bombs were powerful enough to propel sarin from depots in Muthanna and Falluja high into the atmosphere, where winds whisked it hundreds of miles south to the Saudi border. Once over the American encampments, the toxic plume could have stalled and fallen back to the surface because of weather conditions, the paper says. Though troops would have been exposed to low levels of the agent, the authors assert that the exposures may have continued for several days, increasing their impact. Though chemical weapons detectors sounded alarms in those encampments in the days after the January 1991 bombing raids, they were viewed as false by many troops, the authors report. © 2012 The New York Times Company
A specific pattern of neuronal firing in a brain reward circuit instantly rendered mice vulnerable to depression-like behavior induced by acute severe stress, a study supported by the National Institutes of Health has found. When researchers used a high-tech method to mimic the pattern, previously resilient mice instantly succumbed to a depression-like syndrome of social withdrawal and reduced pleasure-seeking — they avoided other animals and lost their sweet tooth. When the firing pattern was inhibited in vulnerable mice, they instantly became resilient. "For the first time, we have shown that split-second control of specific brain circuitry can switch depression-related behavior on and off with flashes of an LED light," explained Ming-Hu Han, Ph.D. External Web Site Policy, of the Mount Sinai School of Medicine, New York City, a grantee of NIH’s National Institute of Mental Health (NIMH). "These results add to mounting clues about the mechanism of fast-acting antidepressant responses." Han, Eric Nestler, M.D., Ph.D. External Web Site Policy,of Mount Sinai, and colleagues, report on their study in the journal Nature. In a companion article, NIMH grantees Kay Tye, Ph.D. External Web Site Policy, of the Massachusetts Institute of Technology, Cambridge, Mass., and Karl Deisseroth, M.D., Ph.D. External Web Site Policy, of Stanford University, Stanford, Calif., used the same cutting-edge technique to control mouse brain activity in real time. Their study reveals that the same reward circuit neuronal activity pattern had the opposite effect when the depression-like behavior was induced by daily presentations of chronic, unpredictable mild physical stressors, instead of by shorter-term exposure to severe social stress.
By Joss Fong What do an orgasm, a multiplication problem and a photo of a dead body have in common? Each induces a slight, irrepressible expansion of the pupils in our eyes. For more than a century scientists have known that our eyes' pupils respond to more than changes in light. They also betray mental and emotional commotion. In fact, pupil dilation correlates with arousal so consistently that researchers use pupil size, or pupillometry, to investigate a wide range of psychological phenomena. And they do this without knowing exactly why our eyes behave this way. "Nobody really knows for sure what these changes do," says Stuart Steinhauer, director of the Biometrics Research Lab at the University of Pittsburgh School of Medicine. He views the dilations as a by-product of the nervous system processing important information. The visual cortex in the back of the brain assembles the actual images we see. But a different, older part of the nervous system—the autonomic—manages the continuous tuning of pupil size (along with other involuntary functions such as heart rate and perspiration). Specifically, it dictates the movement of the iris to regulate the amount of light that enters the eye, similar to a camera aperture. The iris is made of two types of muscle: a ring of sphincter muscles that encircle and constrict the pupil down to a couple of millimeters across to prevent too much light from entering; and a set of dilator muscles laid out like bicycle spokes that can expand the pupil up to eight millimeters—approximately the diameter of a chickpea—in low light. © 2012 Scientific American
by Debora Mackenzie The Toxoplasma parasite is an unusually devious operator. When it infects mice, it alters their behaviour so they become fearless enough to seek out cats and get eaten. But exactly how it did this was a mystery. Now it appears that the parasite hijacks its victim's immune system, causing it to produce a chemical normally found in the brain. The discovery suggests that the brain and immune system might have evolved using similar processes to control their behaviour, including electrical and chemical signals now known mainly in nerves. Toxoplasma gondii spends part of its life in a cat's gut, then spreads to mice via cat droppings. It invades their brains and causes them to behave fearlessly towards cats – quickly returning the parasite to a cat's gut and completing its life cycle. The parasite can use other animals as a host, and can spread to humans via infected, uncooked meat as well as cat droppings. Acute infection can harm a fetus, so pregnant women are told to avoid cat litter boxes. A quarter of people have a lifelong Toxoplasma infection and may suffer psychological effects, including increased recklessness. Antonio Barragan of the Karolinska Institute in Stockholm, Sweden, has now discovered that the parasite's mind-bending abilities could be a side effect of the way it hijacks the immune system. Invaders like Toxoplasma normally get engulfed by white blood cells called dendritic cells (DCs), a process that helps other immune cells learn to recognise them. © Copyright Reed Business Information Ltd.
By Kyle Hill You careen headlong into a blinding light. Around you, phantasms of people and pets lost. Clouds billow and sway, giving way to a gilded and golden entrance. You feel the air, thrusted downward by delicate wings. Everything is soothing, comforting, familiar. Heaven. It’s a paradise that some experience during an apparent demise. The surprising consistency of heavenly visions during a “near death experience” (or NDE) indicates for many that an afterlife awaits us. Religious believers interpret these similar yet varying accounts like blind men exploring an elephant—they each feel something different (the tail is a snake and the legs are tree trunks, for example); yet all touch the same underlying reality. Skeptics point to the curious tendency for Heaven to conform to human desires, or for Heaven’s fleeting visage to be so dependent on culture or time period. Heaven, in a theological view, has some kind of entrance. When you die, this entrance is supposed to appear—a Platform 9 ¾ for those running towards the grave. Of course, the purported way to see Heaven without having to take the final run at the platform wall is the NDE. Thrust back into popular consciousness by a surgeon claiming that “Heaven is Real,” the NDE has come under both theological and scientific scrutiny for its supposed ability to preview the great gig in the sky. But getting to see Heaven is hell—you have to die. Or do you? © 2012 Scientific American
By Michelle Warwicker BBC Nature The youngest members of zebra finch broods "explore more" than older siblings in adult life, say scientists. Researchers investigated how the birds' behaviour was affected by the way their parents cared for them as hatchlings. The team studied broods where females lay and incubate a clutch of eggs over a period of days, resulting in a size hierarchy within the clutch. They found the youngest birds were more likely to explore their environment as adults in search of food. The study, published in Animal Behaviour, tested over 100 captive zebra finches' exploratory behaviour to see whether hatching order, and consequently parental investment, affected their behaviour in adulthood. Late hatched birds are smaller than their older siblings, and it is the larger hatchlings that "get the lion's share" when parents bring in food "because they can reach up higher and beg better," explained research team member Dr Ian Hartley from Lancaster University. Hatching eggs over a span of time, rather than all at once, is known as "hatching asynchrony" and occurs when eggs are incubated as soon as they are laid. For zebra finch, this means that birds born up to four days apart can share the same nest and must compete for food. BBC © 2012
By Kate Shaw Early one morning I caught sight of Morpheus, silhouetted against a pink African dawn. Her long, sloping neck was stretched out as she loped away from me, disappearing over a hill. I followed her to a nearby plain and was met with the unmistakable sound of a group of hyenas squabbling over a carcass. Morpheus entered the fray, first lunging at a smaller male on her right. A moment later, she looked up briefly, her nose and mouth covered in blood, then turned and snapped at a hyena feeding nearby. I’m intimately acquainted with Morpheus and these other hyenas because they have been studied for more than twenty years by various members of the lab where I did my Ph.D. research; I’ve staked these hyenas out at dens for hours on end and followed them as they raced across open plains. From watching these animals, we’ve learned about hyenas’ social system, their physiology, and the conservation challenges they face. But to me, it’s the aggression that is the most fascinating thing about hyenas. It’s rule-based and constrained by specific social norms, but at the same time, it’s incredibly primal and ruthless. Studying aggression has helped us understand what makes hyenas tick, offering us a glimpse into the evolutionary pressures that have made them one of the most unusual and misunderstood species in the animal kingdom. For more than 1000 years, people believed that hyenas were hermaphrodites, since female hyenas have long, fully-erectile pseudopenises that mimic male genitalia. Seeing a hyena play the role of mom while sporting what looks like a penis would bewilder even an astute naturalist. Not only do female hyenas look like males, they are also the more aggressive and socially dominant sex, exhibiting aggression more than three times more often than male hyenas do. © 2012 Scientific American
by Emily Underwood On the reality television show Extreme Makeover: Home Edition, the lucky recipient gets a first look at his newly renovated home. For a split second, his face contorts with—shock? Joy? During intense emotional experiences, there's a fleeting moment when expressions of pleasure and pain are hard to distinguish. In fact, others read intense emotion more effectively by looking at a person's body language than by watching his facial expressions, a new study suggests. Most studies of facial cues rely on a set of stylized, recognizable expressions—perhaps made by actors in photographs. The actors make expressions meant to be obvious enough to translate across cultures: anger, disgust, fear, joy, sadness, and surprise. But these stylized images don't necessarily reflect the expressions that people make in the real world, says Hillel Aviezer, a neuropsychologist at who is now at The Hebrew University of Jerusalem and lead author of the new study, published online today in Science. Moreover, when emotions get particularly extreme, people undergoing fleeting peaks of intense pain, joy, grief, or anger look surprisingly similar, Aviezer says. From the face, at least, "when you compare extreme pain to extreme pleasure, you really can't tell them apart," he says. And yet most people are rarely confused about whether someone is experiencing grief or joy. To figure out what tips us off, Aviezer and his colleagues showed photos of professional tennis players to 45 Princeton University students, randomly divided into three groups of 15. Each tennis player had just won or lost an important match, and the participants rated the players' contorted facial expressions from negative to positive on a scale from 1 to 9, with 5 marking the neutral midway point. One group of participants looked at head-to-toe photos of the players, the second group looked at only the players' bodies, and the third group looked at only their heads. Only the final group had trouble making the correct identification, suggesting that facial expressions alone didn't tell them whether the players were joyous or in despair. © 2010 American Association for the Advancement of Science
By BENEDICT CAREY For years they have lived as orphans and outliers, a colony of misfit characters on their own island: the bizarre one and the needy one, the untrusting and the crooked, the grandiose and the cowardly. Their customs and rituals are as captivating as any tribe’s, and at least as mystifying. Every mental anthropologist who has visited their world seems to walk away with a different story, a new model to explain those strange behaviors. This weekend the Board of Trustees of the American Psychiatric Association will vote on whether to adopt a new diagnostic system for some of the most serious, and striking, syndromes in medicine: personality disorders. Personality disorders occupy a troublesome niche in psychiatry. The 10 recognized syndromes are fairly well represented on the self-help shelves of bookstores and include such well-known types as narcissistic personality disorder, avoidant personality disorder, as well as dependent and histrionic personalities. But when full-blown, the disorders are difficult to characterize and treat, and doctors seldom do careful evaluations, missing or downplaying behavior patterns that underlie problems like depression and anxiety in millions of people. The new proposal — part of the psychiatric association’s effort of many years to update its influential diagnostic manual — is intended to clarify these diagnoses and better integrate them into clinical practice, to extend and improve treatment. But the effort has run into so much opposition that it will probably be relegated to the back of the manual, if it’s allowed in at all. © 2012 The New York Times Company
Link ID: 17542 - Posted: 11.27.2012
By Scicurious Animals don’t handle stress well. I’m not talking about acute stressors, the predator charging at you through the brush, you run away and it’s over. We handle that stress very well indeed. But severe stress, losing a job, a divorce, a death in the family, these can really wear us down. Severe life stressors can not only impact your physical health, they also often occur before the onset of mental illness, particularly major depressive disorder. Depression takes many forms (lack of interest in activities, sleep changes, eating changes, severely depressed mood), but one of the most debilitating ones is the way that it impacts motivation. While some stressors (like, say, a deadline), might before have been a motivator, making you work to get it done, during depression, these stressors become insurmountable obstacles. Things you did before you couldn’t possibly get done now. You’ll never make the deadline. You can’t run the race. Stress can’t motivate you any more. What has changed? To look at this, Lemos et al at the University of Washington, Seattle, looked at one of the signals in response to stress in the brain: corticotropin releasing factor (CRF). CRF is the first step in the process that eventually allows cortisol to be released into the bloodstream, the molecule we usually associate with stress. You can see at the top of the chain there CRF being released from the hypothalamus. From there the next step in the chain is the anterior pituitary, and from there adrenocorticotropic releasing hormone (ACTH) is released, and stimulates the adrenal glands (sitting in little pads of fat above your kidneys) to release cortisol. But in the brain, it’s more complicated than that. CRF isn’t just released from the hypothalamus to the pituitary, it’s released to other regions, too. © 2012 Scientific American
Link ID: 17539 - Posted: 11.27.2012
By Wray Herbert In 2009 a regiment of Danish soldiers, the Guard Hussars, was deployed for a six-month tour in Afghanistan's arid Helmand province, a Taliban stronghold. They were stationed along with British soldiers—270 in all—at a forward operating base called Armadillo. Although none of the Guard Hussars were killed during the tour of duty, they nonetheless experienced many horrors of battle. A commander was seriously injured by a roadside bomb, and a night patrol ended in a firefight that killed and dismembered several Taliban combatants. The Guard Hussars' war experience is graphically depicted in the award-winning documentary film Armadillo, which debuted in 2010. It follows the soldiers from their emotional farewells in Denmark through their months in combat and, finally, back to joyous homecomings and family reunions. The film is a study of the inner lives of young men as they experience the excitement and camaraderie, the tedium and—mostly—the terror and trauma of war. Coincidentally, these same soldiers were also the subject of another, very different kind of study. At the same time that the film was being shot, the men were part of a larger group of Danish soldiers who were being scientifically observed and tested for emerging symptoms of post-traumatic stress disorder, or PTSD. A large team of Danish and American psychological scientists, led by Dorthe Berntsen of Aarhus University, wanted to do what had never been done before in this field of research: instead of studying soldiers who were already suffering from PTSD, they decided to assess young recruits before they were sent off to war, when they were still relatively unscathed, then to record them during the war experience, and finally to follow them back home and through several months of readjustment. In this way, the scientists hoped to see why some soldiers develop PTSD and others do not and how the symptoms of the disorder progress. © 2012 Scientific American
By GRETCHEN REYNOLDS Is playing football like falling in love? That question, which would perhaps not occur to most of us watching hours of the bruising game this holiday season, is the focus of a provocative and growing body of new science examining the role of oxytocin in competitive sports. Oxytocin is, famously, the “love hormone,” a brain peptide known to promote positive intersocial relations. It makes people like one another, especially in intimate relationships. New mothers are awash in oxytocin (which is involved in the labor process), and it is believed that the hormone promotes bonding between mother and infant. New-formed romantic couples also have augmented bloodstream levels of the peptide, many studies show. The original attraction between the lovers seems to prompt the release of oxytocin, and, in turn, its actions in the brain intensify and solidify the allure. Until recently, though, scientists had not considered whether a substance that promotes cuddliness and warm, intimate bonding might also play a role in competitive sports. But the idea makes sense, says Gert-Jan Pepping, a researcher at the Center for Human Movement Sciences at the University of Groningen in The Netherlands, and the author of a new review of oxytocin and competition. “Being part of a team involves emotions, as for instance when a team scores, and these emotions are associated with brain chemicals.” Copyright 2012 The New York Times Company
The Associated Press Chimpanzees going through a midlife crisis? It sounds like a setup for a joke. But there it is, in the title of a report published Monday in a scientific journal: "Evidence for a midlife crisis in great apes." So what do these apes do? Buy red Ferraris? Leave their mates for some cute young bonobos? Uh, no. "I believe no ape has ever purchased a sports car," said Andrew Oswald, an author of the study. But researchers report that captive chimps and orangutans do show the same low ebb in emotional well-being at midlife that some studies find in people. That suggests the human tendency toward midlife discontent may have been passed on through evolution, rather than resulting simply from the hassles of modern life, said Oswald, a professor of economics at the University of Warwick in England who presented his work Monday in the Proceedings of the National Academy of Sciences. A second study in the journal looks at a younger age group and finds that happiness in youth can lead to higher income a few years down the road. Several studies have concluded that happiness in human adults tends to follow a certain course between ages 20 and 70: It starts high and declines over the years to reach a low point in the late 40s, then turns around and rises to another peak at 70. On a graph, that's a U-shaped pattern. Some researchers question whether that trend is real, but to Oswald the mystery is what causes it. "This is one of the great patterns of human life. We're all going to slide along this U for good or ill," he said. "So what explains it?" © CBC 2012
By BENEDICT CAREY Hundreds of Iraq and Afghanistan veterans with post-traumatic stress have recently contacted a husband-and-wife team who work out of their home in suburban South Carolina to seek help. Many are desperate, pleading for treatment and willing to travel to get it. The soldiers have no interest in traditional talking cures or prescription drugs that have given them little relief. They are lining up to try an alternative: MDMA, better known as Ecstasy, a party drug that surfaced in the 1980s and ’90s that can induce pulses of euphoria and a radiating affection. Government regulators criminalized the drug in 1985, placing it on a list of prohibited substances that includes heroin and LSD. But in recent years, regulators have licensed a small number of labs to produce MDMA for research purposes. “I feel survivor’s guilt, both for coming back from Iraq alive and now for having had a chance to do this therapy,” said Anthony, a 25-year-old living near Charleston, S.C., who asked that his last name not be used because of the stigma of taking the drug. “I’m a different person because of it.” In a paper posted online Tuesday by the Journal of Psychopharmacology, Michael and Ann Mithoefer, the husband-and-wife team offering the treatment — which combines psychotherapy with a dose of MDMA — write that they found 15 of 21 people who recovered from severe post-traumatic stress in the therapy in the early 2000s reported minor to virtually no symptoms today. Many said they have received other kinds of therapy since then, but not with MDMA. The Mithoefers — he is a psychiatrist and she is a nurse — collaborated on the study with researchers at the Medical University of South Carolina and the nonprofit Multidisciplinary Association for Psychedelic Studies. © 2012 The New York Times Company
By Maggie Fox, NBC News Researchers trying to find a way to treat multiple sclerosis think they’ve come up with an approach that could not only help patients with MS, but those with a range of so-called autoimmune diseases, from type-1 diabetes to psoriasis, and perhaps even food allergies. So far it’s only worked in mice, but it has worked especially well. And while mice are different from humans in many ways, their immune systems are quite similar. “If this works, it is going to be absolutely fantastic,” said Bill Heetderks, who directs outside research at the National Institute of Biomedical Imaging and Bioengineering, part of the National Institutes of Health, which helped pay for the research. “Even if it doesn’t work, it’s going to be another step down the road.” In autoimmune disease, the body’s immune cells mistakenly attack and destroy healthy tissue. In MS, it’s the fatty protective sheath around the nerves; in type-1 or juvenile diabetes it’s cells in the pancreas that make insulin; in rheumatoid arthritis it’s tissue in the joint. Currently, the main treatment is to suppress the immune system, an approach that can leave patients vulnerable to infections and cancer. The new treatment re-educates the immune cells so they stop the attacks. The approach uses tiny little balls called nanoparticles made of the same material used to make surgical sutures that dissolve harmlessly in the body. They’re attached to little bits of the protein that the immune cells are attacking, the researchers report in Sunday’s issue of the journal Nature Biotechnology. © 2012 NBCNews.com
In 2009, Susannah Cahalan was a healthy 24-year-old reporter for the New York Post, when she began to experience numbness, paranoia, sensitivity to light and erratic behavior. Grasping for an answer, Cahalan asked herself as it was happening, "Am I just bad at my job — is that why? Is the pressure of it getting to me? Is it a new relationship?" But Cahalan only got worse — she began to experience seizures, hallucinations, increasingly psychotic behavior and even catatonia. Her symptoms frightened family members and baffled a series of doctors. After a monthlong hospital stay and $1 million worth of blood tests and brain scans that proved inconclusive, Cahalan was seen by Dr. Souhel Najjar, who asked her to draw a clock on a piece of paper. "I drew a circle, and I drew the numbers 1 to 12 all on the right-hand side of the clock, so the left-hand side was blank, completely blank," she tells Fresh Air's Dave Davies, "which showed him that I was experiencing left-side spatial neglect and, likely, the right side of my brain responsible for the left field of vision was inflamed." As Najjar put it to her parents, "her brain was on fire." This discovery led to her eventual diagnosis and treatment for anti-NMDA receptor encephalitis, a rare autoimmune disease that can attack the brain. Cahalan says that doctors think the illness may account for cases of "demonic possession" throughout history. Cahalan's new memoir is called Brain on Fire: My Month of Madness. ©2012 NPR
by Greg Miller Seeing someone yawn or hearing someone laugh makes you likely to follow suit. The same goes for scratching an itch. Now, for the first time, researchers have investigated the neural basis of contagious itch, identifying several brain regions whose activity predicts how susceptible people are to feeling itchy when they see someone else scratch. Researchers in the United Kingdom showed volunteers video clips of people scratching an arm or a spot on their chest. Sure enough, subjects reported feeling more itchy, and most scratched themselves at least once during the experiment. When a subset of the volunteers watched the videos inside an functional magnetic resonance imaging scanner, the scans revealed activity in several of the same brain regions known to fire up in response to an itch-inducing histamine injection. Activity in three of these areas correlated with subjects' self-reported itchiness, the team reports online today in the Proceedings of the National Academy of Sciences. Personality tests suggest that the trait that best predicts susceptibility to contagious itch is neuroticism, not empathy, as some researchers have suggested. © 2010 American Association for the Advancement of Science
By Laura Sanders The effects of a baby’s rough start can linger. An early stressful environment during a baby girl’s first year was associated with altered brain behavior and signs of anxiety in her late teens, scientists report online November 11 in Nature Neuroscience. Although the results are preliminary, they may help reveal how negative experiences early on can sculpt the brain. Studies in animals have pointed out how tough times in childhood can influence the brain and the animals’ behavior later in life. But it’s been hard to figure out how that process works in people, says Lawrence Price, a psychiatrist and clinical neuroscientist at Brown University in Providence, R.I. “One of the real advances of this paper is that it helps move us along on that pathway,” he says. The study, led by Cory Burghy of the University of Wisconsin–Madison, drew from the Wisconsin Study of Family and Work, which in 1990 recruited pregnant women in southern Wisconsin at prenatal visits. Three times during the first year of their babies’ lives, the mothers reported whether they were experiencing stressful situations such as depression, marital conflict, money woes or parenting stress. Researchers assumed that women who reported higher stress levels created a more stressful situation for their baby. Four and a half years later, daughters whose moms reported higher levels of stress had more of the stress hormone cortisol in their blood. That observation suggests the girls had trouble shutting down a hyperactive stress response. The same effect wasn’t found in boys. © Society for Science & the Public 2000 - 2012
By MICHAEL TRIMBLE IN 2008, at a zoo in Münster, Germany, a gorilla named Gana gave birth to a male infant, who died after three months. Photographs of Gana, looking stricken and inconsolable, were ubiquitous. “Heartbroken gorilla cradles her dead baby,” Britain’s Daily Mail declared. Crowds thronged the zoo to see the grieving mother. Sad as the scene was, the humans, not Gana, were the only ones crying. The notion that animals can weep — apologies to Dumbo, Bambi and Wilbur — has no scientific basis. Years of observations by the primatologists Dian Fossey, who observed gorillas, and Jane Goodall, who worked with chimpanzees, could not prove that animals cry tears from emotion. In his book “The Emotional Lives of Animals,” the only tears the biologist Marc Bekoff were certain of were his own. Jeffrey Moussaieff Masson and Susan McCarthy, the authors of “When Elephants Weep,” admit that “most elephant watchers have never seen them weep.” It’s true that many mammals shed tears, especially in response to pain. Tears protect the eye by keeping it moist, and they contain antimicrobial proteins. But crying as an embodiment of empathy is, I maintain, unique to humans and has played an essential role in human evolution and the development of human cultures. Within two days an infant can imitate sad and happy faces. If a newborn mammal does not cry out (typically, in the first few weeks of life, without tears) it is unlikely to get the attention it needs to survive. Around three to four months, the relationship between the human infant and its environment takes on a more organized communicative role, and tearful crying begins to serve interpersonal purposes: the search for comfort and pacification. As we get older, crying becomes a tool of our social repertory: grief and joy, shame and pride, fear and manipulation. © 2012 The New York Times Company
By Tia Ghose, LiveScience Humans can smell fear and disgust, and the emotions are contagious, according to a new study. The findings, published Nov. 5 in the journal Psychological Science, suggest that humans communicate via smell just like other animals. "These findings are contrary to the commonly accepted assumption that human communication runs exclusively via language or visual channels," write Gün Semin and colleagues from Utrecht University in the Netherlands. Most animals communicate using smell, but because humans lack the same odor-sensing organs, scientists thought we had long ago lost our ability to smell fear or other emotions. To find out, the team collected sweat from under the armpits of 10 men while they watched either frightening scenes from the horror movie "The Shining" or repulsive clips of MTV's "Jackass." Next, the researchers asked 36 women to take a visual test while they unknowingly inhaled the scent of men's sweat. When women sniffed "fear sweat," they opened their eyes wide in a scared expression, while those smelling sweat from disgusted men scrunched their faces into a repulsed grimace. (The team chose men as the sweat donors and women as the receivers because past research suggests women are more sensitive to men's scent than vice versa.) © 2012 NBCNews.com