Dan Joling / AP

A nearly full moon sets over waters of Cook Inlet and a children's whale slippery slide just before sunrise on Tuesday, at Elderberry Park in downtown Anchorage, Alaska. Anchorage's next full moon is Wednesday.

When there's a full moon (like the one Wednesday), there's a tendency to blame some people's strange behavior on it. But a new Canadian study dismisses this popular belief and suggests that more people with psychological problems do not show up at hospital emergency rooms during a full moon.

Researchers found little evidence that the moon's lunar cycles were linked to an increased incidence of mental health concerns. 

In other words, the moon's behavior seems to have no effect on human behavior on planet Earth. Sure, the word "lunatic" derives from the Latin word "luna" for "moon," but science has found little connection between the moon and madness.

Even so, that won't stop some of us from thinking that lunar cycles can influence psychological symptoms. By one estimate, 80 percent of nurses and 64 percent of doctors who work in the emergency department believe it affects patients' mental health.

In the study, which will appear in the journal General Hospital Psychiatry, researchers reviewed medical records from two hospitals in Montreal over a three-year period. They looked at nearly 800 patients who came to the emergency room for unexplained chest pains, meaning doctors aren't sure what caused their heart trouble.

Researchers studied unexplained chest pains because people with this complaint often suffer from many psychological difficulties, including panic attacks, anxiety and mood disorders, and suicidal thoughts.

They also investigated this topic because the research team was already conducting a study on panic attacks and unexplained chest pains. And the emergency department personnel would often make comments, such as "This would be a good night for research because it's a full moon," says study researcher William Foldes-Busque, PhD, an assistant professor of psychology at the University of Quebec in Montreal, Canada. So, experimenters knew some health professionals already had this perception in their heads, but they wanted to see if the idea had any truth to it.

After patients completed a mental health evaluation, scientists then analyzed data to find out if their psychological symptoms revealed any seasonal patterns or lunar phase influence. Researchers were able to determine which one of the moon's four phases -- new moon, first quarter, full moon, or last quarter -- was present on the day each patient came to the emergency room.

The study found that lunar cycle had no influence on the occurrence of psychological problems, such as panic attacks, anxiety and mood disorders, or suicidal thoughts. The only exception was a 32% drop in the frequency of anxiety disorders during the moon's last quarter. 

"We don't know for sure why this happened," says Foldes-Busque.

Other studies have looked at admissions to psychiatric hospitals, calls to crisis hotlines, or homicide rates, and also failed to turn up a link between the moon's illumination and behavior changes. But if you talk to health professionals or police officers, they may think there's more nuttiness and craziness during a full moon. 

It's possible that people are more prone to notice -- and remember -- a full moon, so they may link any strange behaviors they see that day to it. And perhaps when people act odd during other times of the month, they're just considered weird -- no further explanations given.

Foldes-Busque says it's possible the moon affects mental health in other ways. "I've heard that the full moon may affect sleep, mostly because of increased luminosity," he says.

What's his advice for today's full moon? "Don't do anything special or change anything because of it."

Related: 

Do you hear what I hear? Your brain on Christmas music

Coffee helps you see the bright side

Want more weird health news? Find The Body Odd on Facebook.

Noah Berger / AP file

All those holiday shoppers...and all that holiday music. Can your brain handle it?

Shana McGough likes Christmas music, until she hears too much of it.

"I think at first Christmas music is nice, it's nostalgic, and it gets me into the holiday spirit," says the writer from Escondido, Calif. Then, "it gets old, and it can start to feel like a part of a giant sales machine trying to bleed me dry."

She also suspects that for anyone of a different faith who doesn't celebrate Christmas,"holiday music must be beyond annoying, right into offensive."

If it’s not started already, by the time the Thanksgiving meal is devoured and the stores open for Black Friday, Christmas music will be inescapable. After hearing 'Rockin' Around the Christmas Tree' and 'Frosty the Snowman' for the umpteenth time, you might be hoping for a silent night.

Earlier this month Canada's top pharmacy chain Shoppers Drug Mart Corp. heeded shopper complaints and put the holiday music on pause until later in the season. Even for people who celebrate Christmas, listening to the same seemingly inescapable seasonal songs over and over again may be incredibly irritating.

Endless loops of “Rudolph, the Red-Nosed Reindeer” or any tinsel-y tune can have a psychological impact known as the 'mere exposure effect,' says Victoria Williamson, Ph.D, who conducts research on the psychology of music at Goldsmiths, University of London. There's a U-shaped relationship between the amount of times we hear music that we like and our subsequent reaction to it, she says.

As Williamson puts it, at first we like music a bit, then we like it more and more until it hits a peak. And then we crash down -- we have overheard it. That's when boredom and annoyance at the repetition of the same sound hits home. "Anyone who has worked in a Christmas store over the holidays will know what I'm talking about," Williamson says. When asked why holiday music seems to have a polarizing effect, driving some people crazy while others like, or at least, can tolerate it, Williamson suggests that music's effect on us in any situation depends on our own psychological state.

People who are already stressed out about the holidays -- worrying about money, traveling, or seeing relatives -- may find the musical reminder of the cause of their stress very unwelcome, she says. But those who approach the holidays in a receptive, relaxed state are more likely to get a boost from the happy associations -- childhood memories, family gatherings, or the holiday's religious meaning -- triggered by holiday music.

Of course, the reason Christmas music is played in every department store, supermarket from Thanksgiving through December. Music can put us in the mood to spend money, research suggests.

"We've shown that 'holiday appropriate' music combined with congruent 'holiday scents' can influence shoppers by increasing the amount of time they spend in a store, their intention to revisit it, and intention to purchase," says Eric Spangenberg, Ph.D, dean of the College of Business at Washington State University in Pullman, who has studied the  influence of music on holiday shopping.

He says that some types of music work better than others. "Slower tempo music slows down shoppers, and they spend more time and money in a store," Spangenberg explains. Faster-paced pieces move people through the store quicker than retailers would like.

For Charlie Muldoon, only certain types of holiday music can put him in a good mood.

"I find the traditional songs sung by the great artists of the 50s and 60s or the funny songs about 'Grandma Getting Run Over by a Reindeer' put a smile on my face," says the Washington, DC-based professional polo player. 

"But those remakes by commercial singers and rappers make me want to go postal," Muldoon confesses. And some sounds make him forget the season's peace on earth, goodwill toward men sentiment. "Those 'elevator' versions of holiday music make me want to take a bat to the machine that plays them," he says.

As long as Christmas songs are played after Thanksgiving, Mary Leach, a public relations professional who lives in Cambridge, Mass., doesn’t mind. To her, "Christmas [music and decorations] much prior to Turkey Day is just plain wrong."

More from The Body Odd: 

• See Jesus in toast? Science explains the mind trick
• Itching is contagious. I'm scratching already 
• Even your strangest dreams are rooted in reality

Want more weird health news? Find The Body Odd on Facebook.

Getty Images stock

This is no laughing matter (or maybe it is): A small British study has found that laughter can increase your tolerance of pain. It seems that cracking up in the company of other people releases endorphins, the same feel-good brain chemicals triggered while exercising.

Laughter is helpful when you're hurting because it's hard work for the body. A hearty, sustained laugh is a good workout for muscles in the chest and lungs, and this can trigger the release of endorphins to mask the pain, says Robin Dunbar, PhD, a professor of evolutionary psychology at Oxford University, who led the study. When endorphin levels increase, a person's pain threshold rise, he explains. 

For the study, published in the Proceedings of the Royal Society B, scientists ran a series of six different experiments in the lab and one in a real-world setting, during live stage performances at the Edinburgh Fringe Festival. Many of the tests were done in small groups because other research has shown that laughter is 30 times more likely to occur in a social situation than when you're alone.

In some studies, half of the volunteers watched a comedy video -- ranging from episodes of "South Park" and "Friends" to "Mr. Bean" and "The Simpsons" -- while the others viewed a documentary on dull stuff like golf instruction, pet training, or a nature show. 

Each participant's individual pain threshold was tested before and after watching the videos, using such pain-inducing techniques as an increasingly tighter blood pressure cuff around the upper arm or a frozen wine cooler sleeve placed on the forearm and held there until the person couldn't take it any longer. Pain tolerance was considered a proxy measure of endorphin levels.

Researchers also recorded the amount of time participants spent laughing. But polite titters wouldn't cut it; only relaxed social laughter that stretched smile muscles in the face counted.

Pain tolerance was shown to be higher in men and women who watched funny videos, but they stayed the same or were lower in those who didn't. Scientists were also able to tease out that a person's ability to handle more pain was due to the laughter itself and not just because it put someone in a better mood.

Laughter is definitely some of the best medicine for pain, says Dunbar. It seems that endorphins tune up the immune system, so triggering their release through laughter helps you recover from disease and allows the body to resist infection, he explains

Would some comic relief help those suffering from chronic pain? Presumably, the more you engage in social events that involve laughter, you'll be better able to bear chronic pain, Dunbar says.

"No doubt the pharmaceutical companies won't like it, but laughter would save on hospital bills," he points out.

Related:

People who don't laugh easily are only fooling themselves

Your doc's sick sense of humor is good for your health

We may hate laugh tracks -- but they work

Want more weird health news? Find The Body Odd on Facebook.

Do you see a face in the back of this train? It's one of the images used by researchers to figure out which people are most inclined to see faces in objects.

People have claimed to see Jesus in their burnt toast. Others have spotted the Virgin Mary in a 10-year-old grilled cheese sandwich, or seen a vague resemblance to Elvis in an oddly shaped potato chip. 

Courtesy of Tapani Riekki

Is this rock looking at you? Researchers showed subjects a group of images, like this one, to find out who was most likely to see faces on inanimate objects.

These folks aren't wacky or crazy, and they don't need their eyes examined. They're experiencing what's known as the illusory face perception, a tendency to see face-like areas in non-human things. They may see facial features in nature (in cloud formations or rock ledges) or inanimate objects (food or household items).

Now, a small study from Finland, published in the journal Applied Cognitive Psychology, has attempted to find out what types of people are most likely people to pick up on these visual perceptions.

"An ability to see faces is more common in some people than others due to differences in how our brains process information," says study author Tapani Riekki, a doctoral student in the division of cognitive psychology and neuropsychology at the University of Helsinki. "It's normal, and actually fun, that our mind plays tricks and triggers the face perception when no actual faces are present," he suggests.

Researchers wanted to determine if religious and paranormal beliefs played a role in a person's ability to perceive a face when no face is truly there. So they recruited 47 men and women, and they compared 19 people who had a favorable opinion of paranormal powers -- such as clairvoyance and astrology -- to a group of 20 participants who were skeptical of these phenomena.

A second analysis compared results from 20 people who considered themselves religious to 19 non-religious individuals.

NBCNews.com

In 2004, a Florida woman sold this grilled cheese sandwich, which some say features the face of the Virgin Mary, for $28,000 on ebay.

In the study, researchers had volunteers complete a detection task: Participants viewed 185 color photos on a computer screen (98 had face pictures, 87 did not) and they had four seconds to determine if they could detect a face-like area with eyes and a mouth within each picture. If they saw a face, they were asked to point to its location.

The images included landscapes and nature scenes as well as buildings and objects. Some face-like features were staged (an arrangement of tools on a table), while others were found naturally in the real world (in rock formations or tree trunks).

The researchers purposely chose "face" photos that were harder to detect to better show the individual differences between all four experimental groups.

The study found that religious people and paranormal believers perceived more face-like areas when some were present compared to non-religious individuals and skeptics.  But believers also saw more face-like patterns in pictures when none were there.

"Our results show that the difference between the groups is not at the perception level but at the level of interpreting," says Riekki. More specifically, they found that the difference was in how much information was needed to raise the perception of "something face-like" in the image.

Citrus Christ? Cheesus? 13 religious sightings

Paranormal and religious believers had a lower criteria for believing they saw a face, and they also rated faces as more face-like and showing stronger emotions. These findings imply believers may be more susceptible to the suggestion that faces may be present in the images.

"Even a small amount of information, perhaps just two dots that slightly resemble eyes may trigger the idea that this could be face-like," Reikki explains.

"In other words, the believer groups found more meaningful patterns in ambiguous pictures," he points out.

See more religious sightings

More from The Body Odd:

Face of pain? Man's image seen in ultrasound

Itchiness is contagious, just like yawning

Guys with shaved heads seem tougher, study finds

Young people can't read emotion on wrinkled faces

Want more weird health news? Find The Body Odd on Facebook.

Lew Robertson / Getty Images

Screeech! The sound of nails on a chalkboard are in the top 5 worst sounds, according to a new study.

Which sounds drive our ears absolutely bonkers?

A British study rated the screechy scrape of a sharp knife along the surface of a ridged metal bottle as the most unpleasant sound. It earned the top spot in a recent ranking of 75 different sounds.

A steel fork scraping along a glass finished a close second among the nastiest noises heard by 50 college students during the research. And the annoying squeal of chalk on a blackboard was the third most awful sound in this small experiment , in which listeners rated each sound on a nine-point scale from 0 for least unpleasant to 9 for most unpleasant.

The study volunteers all had good hearing and used headphones to listen to a variety of natural and man-made sound recordings, which ranged from a cat screaming and a clarinet squeaking to a fire alarm blaring and an engine revving.

Interestingly, the always cringe-inducing sound of fingernails on a blackboard came in fifth on the rankings -- behind a ruler on a bottle but ahead of a woman's scream.

"It was a bit surprising that a female scream and a baby's cry were rated lower than the scratchy sounds, such as a knife on a bottle," says study author Sukhbinder Kumar, Ph.D., a neuroscientist at Newcastle University Medical School in the U.K.

He says the reason the scratchy sounds may have scored higher may have to do with the acoustic structure of sounds that result from scraping actions. Scratchy noises, like knife on glass, may be the most unpleasant because more of the sound's energy is concentrated in the frequency band of 2000 to 5000 Hz, where our ears are most sensitive. (Screams also have energy in the same frequency band, but its concentration is less.)

In a new study published in The Journal of Neuroscience, Kumar and his colleagues built upon this earlier research to understand the brain mechanism behind why people perceive certain sounds to be so unpleasant.

They asked 13 healthy adults to listen to the same sounds as they previously tested while in a functional MRI machine. Volunteers rated the sounds on a scale from 1 (least unpleasant) to 5 (most unpleasant).

This time, study participants rated chalk on a blackboard at the worst sound while they found bubbling water to be the most soothing. Kumar suspects that the noisy and confining quarters of the MRI machine and the smaller number of participants may have contributed to the slight differences in results between this research and the earlier study.

The brain scans allowed the scientists to see the interaction between the sensory (auditory) part of the brain, involved in hearing, and the emotional part of the brain (the amygdala) in response to the various noises. 

What they found was that the emotional part of the brain modulates, or changes, the activity of the sensory part of the brain based on the emotional value of the sound. Kumar says that if a sound is "highly unpleasant," which may have the potential to cause harm, the emotional part of the brain heightens up the response of the sensory cortex, which provokes a negative reaction to its perceived unpleasantness.

Kumar suggests that these new findings may help shed light on the brain's reaction to disorders such as migraine and tinnitus (ringing in the ears), in which people are super sensitive to the unpleasant aspects of sound.

Want to test your reaction to some of the sounds used in both studies? Listen to some of the sounds here:

The 10 worst sounds based on both studies were:

1.  Knife on a bottle

2.  Fork on a glass

3.  Chalk on a blackboard

4.  Plastic ruler on a bottle

5.  Nails on a blackboard

6.  Female scream

7.  Angle grinder tool used on a hollow metal pipe

8.  Bicycle breaks squealing

9.  Baby crying

10. Electric drill running at a range of speeds

The 4 least unpleasant sounds were:

1.  Applause

2.  Baby laughing

3.  Thunder

4.  Water flowing

Want more weird health news? Find The Body Odd on Facebook.

New England Journal of Medicine, copyright 2012

This man's deep skin folds that resemble the surface of the brain are the result of a rare condition called cutis verticis gyrata.

The strange folds and furrows covering a Brazilian man's entire scalp was neither a funky new look nor a hipster trend. Rather the 21-year-old's bizarre looking scalp with its deep skin folds in a pattern said to resemble the surface of the brain is a sign of a rare medical condition known as cutis verticis gyrata.

In this week's New England Journal of Medicine, two Brazilian doctors describe this young man's case and share a picture of its odd appearance. When he was 19, the skin on his scalp started to change. It grew thicker, forming many soft, spongy ridges and narrow ruts.

Even his hair had an unusual configuration. It was normal in the furrows but sparser over the folds as is common for this strange scalp condition. No doubt, visits to the barber shop as well as washing his squishy scalp and combing his hair were peculiar experiences.

Despite the extent of his scalp affected, "the patient did not have the habit of covering his head," with a hat, for instance, says Dr. Karen Schons a dermatologist at the Hospital Universitario de Santa Maria, who examined the patient and co-authored the case study. In fact, the case study reports that "the condition did not bother him cosmetically."

Cutis verticis gyrata occurs much more commonly in men, and it typically develops not long after puberty occurs. Doctors aren't sure exactly what causes the scalp changes that lead to its weird appearance.

In this Brazilian man's case, no one else in his family had the condition, and he did not have any symptoms because of it. He was intellectually impaired and had performed poorly in school, but this was not linked with the skin folds and furrows on his scalp.

In fact, his doctors found he had no symptoms of neurological or psychiatric disorders, even though cutis verticis gyrata has sometimes been associated with cognitive disabilities or other brain-related disorders, such as schizophrenia and seizures.

"It's a benign and essentially aesthetic condition," explains Schons. Although his head probably attracted some curious stares, this man wasn't self-conscious about it. He needed no treatment.

Schons says there are surgical methods that can correct some of the disfigurement, but it may not be a good option for patients with extensive scalp involvement.

Doctors saw the young man a year after he was diagnosed, and his scalp looked the same and he continued to have no health concerns or concerns about his appearance. 

More from the Body Odd:

Boredom has more to do with you than the situation

Your weird attraction to Prince Harry: A theory

Want more weird health news? Find The Body Odd on Facebook.

Slideshow: Bald and beautiful

EPA. AP

Launch slideshow

Sometime in his late 30s, after his hair had been thinning for several years, Dr. Albert Mannes decided to shave what was left of his mane. He then noticed a curious thing: "Strangers were more standoffish, more deferential," he recalls.

"I found that people treated me differently once I started shaving my head, which made me wonder whether my experience was unique," says Mannes.

This led Mannes, a lecturer at the Wharton School, at the University of Pennsylvania, to design three experiments that tested other people's perception of men with shaved heads. His findings appear in the journal Social Psychological and Personality Science.

All three studies found similar results: A man's shorn scalp was linked with dominance. In other words, men with shaved heads were perceived as powerful by others.

It seems that closely cropped or bald domes have a certain manly swagger to them that project a powerful look.

In the first study, 59 college students looked at 25 photographs of men enrolled in a business school program. Ten of the men had shaved heads while the rest wore their hair in various styles and lengths.

Volunteers rated the photos of men with shorn scalps as more dominant, meaning they looked more powerful, influential, and authoritative than those with a full head of hair.

In a second experiment, 344 adults were shown photographs of four different men. One photo was of the man's real hair and a second shot of him had been digitally altered to remove all of it.

Adults rated men with the digitally shaved heads as more dominant than his coiffed counterpart, an effect researchers say was largely due to perceiving men with shorn scalps as having more confidence and masculinity.

In addition, men without much hair were viewed as nearly an inch taller and 13 percent stronger than men with plenty of it. Although a shaved head had its advantages, men were rated as less attractive and looking nearly four years older than guys with full heads of hair.

Why is a nearly bare head perceived as more dominant? Mannes offers three explanations.

For one, he points to stereotypes. "Shaved heads are found in American culture in traditionally masculine professions, such as the military, law enforcement, and sports," Mannes explains.

A second is that a man who shaves his head is viewed as unconventional. And there's some evidence that the powerful are less inhibited about violating conventional norms, he says.

Finally, Mannes suggests that since "Society places such a high aesthetic value on hair, it takes confidence for a man to dispense with it."

In a third experiment, no photographs were used and more than 500 adults rated their perception of a man based solely on a written physical description of him. All volunteers read the exact same profile except for the description of his hair, which portrayed him as having thick brown hair, thinning brown hair, or a shaved head.

The man described as having a shaved head was rated highest in dominance, masculinity, leadership potential, and strength. The guy with thick tresses scored higher for attractiveness than a shorn scalp and slightly higher on confidence.

The dude with thinning hair scored the lowest on every trait except for norm violation. 

"Men with thinning hair may improve their self-esteem and how they are perceived by others by shaving," Mannes suggests.

He advises men who are getting sparse on top "to stop fighting Mother Nature and try the shaved look."

Related: 

• Why the whole bar sings along to certain songs
• Younger people can't read emotions on wrinkly faces

Want more weird health news? Find The Body Odd on Facebook.

The New England Journal of Medicine

A 30-year-old woman with a history of bulimia was trying to demonstrate to her friends that she no longer had a gag reflex -- and then she swallowed the knife she was using to demonstrate.

Playing with a knife is risky, as one young woman learned the hard way.

A 30-year-old woman who suffered from bulimia was showing off for her sister. To prove that she no longer had a gag reflex, she stuck a table knife to the back of her throat and unexpectedly laughed during her demonstration.

The giggles accidentally sent the knife sliding down her throat, and the result was no laughing matter: She swallowed the knife and soon started throwing up blood and having chest pain.

Fortunately for her, she chose a table knife, not the sharpest knife in the drawer -- but even so, it quickly landed her in the emergency room. In a case reported in this week's New England Journal of Medicine, X-rays revealed the knife was stuck in her esophagus and the upper part of her stomach.

She needed a "rigid esophagogastroduodenoscopy" to remove the knife. This medical procedure involves inserting a tube with a camera into the throat and advancing it down to the esophagus.

"This allows the removal of the knife under direct vision using forceps as well as inspecting the GI tract," says Dr. Aida Venado, who, along with Dr. Sarah Prebil, authored the case study and treated the woman when both were internal medicine residents at Emory University School of Medicine in Atlanta.

Doctors found no immediately visible cuts from the knife in her GI tract. But since these tiny tears may be hard to spot, they did a second test in which they gave the woman a special liquid to drink to see if there were any leaks in her digestive system. None were found.

"The patient was very fortunate to have a good outcome," says Venado. The risks of swallowing a "foreign body" as the knife is referred to in medical circles, include perforating the GI or respiratory tract, injury to major blood vessels, and a serious infection, explains Venado.

"It definitely helped that the object was removed promptly," she says. 

But sadly, this wasn't the first time the woman had swallowed a knife. Her husband told doctors that his wife had also swallowed a knife four years earlier, which had required surgery to remove it.

It's unclear what circumstances had brought about the earlier episode, yet she did have a surgical scar in her abdomen as proof of the incident.

After a few days in the hospital following the latest knife swallowing episode, doctors transferred the woman to the inpatient psychiatric unit for help in treating her bulimia.

Dr. Venado says she doesn't see too many patients who have swallowed unusual objects. But more common culprits are meat bones, coins, batteries, and this time of year, wire bristles from grill-cleaning brushes.

Accidentally or intentionally swallowing these foreign objects can be a life-threatening emergency, where careful removal may be needed, Venado suggests. 

Although this woman's story turned out OK, it might have been helpful for her to have a normally functioning gag reflex in response to placing a knife down her throat.

Related:

• Woman's breast implant disappears during Pilates
• Engineer lived with bullet in his head for 8 decades
• Swallowed pen still works 25 years later
• X-ray reveals thermometer in woman's lung

Want more weird health news? Find The Body Odd on Facebook.

Everyone dreams. But less than 1 percent of adults have a rare condition that causes them to act out their dreams while asleep.

During a vivid dream involving lots of action, people with REM sleep behavior disorder, (RBD) may punch, kick, scream, shout, swear or grab someone while sleeping or they may jump out of bed -- injuring themselves or hurting a bedmate in the process. 

RBD episodes happen during rapid-eye-movement (REM) sleep, a stage of shut-eye when dreaming occurs, or roughly every two hours.

Usually the body is "paralyzed" during REM sleep. But this doesn't happen in people with RBD, so their arms and legs are free to move while dreaming. As a result, if someone with RBD is dreaming of being attacked, they may fight back in their sleep. There's medication to treat RBD symptoms, yet doctors have previously known little about who is affected by the disorder other than it is more common in men and typically strikes people after age 50.

For reasons that are still unclear, REM sleep behavior disorder also seems to increase a person's risk for Parkinson's disease and one type of dementia. Some studies have suggested that more than 50 percent of those with this rare sleep disorder may go on to develop a neurodegenerative disease.

To learn more, a recent study published in the journal Neurology tried to determine the risk factors for RBD and whether they were similar to those for Parkinson's disease or dementia.

They compared the lifestyle habits of 347 people with RBD to the same number of people who didn't have this sleep problem but were similar in age and gender. 

The study identified several potential risk factors for RBD, including having a previous head injury, being a farmer, and working in a job with pesticide exposure. All three of these risks have also been linked with Parkinson's disease.

Researchers also found that people who had fewer years of education increase their chances of RBD.

"Many of the risk factors for RBD are the same as for Parkinson's disease, however, it is ultimately where they differ that can teach us the most," says study author Dr. Ronald Postuma, a neurologist and associate professor at McGill University in Montreal, Canada.

One important difference scientists found was that people who smoke were more likely to develop RBD, but nicotine has been shown to reduce the odds of Parkinson's disease. A second difference is that coffee drinking was not linked with the sleep disorder while other studies have suggested it helps protect against Parkinson's disease.

Postuma suspects that in some people, REM sleep behavior disorder can be an important sign of early Parkinson's disease. In these early stages, he says the disease may affect areas of the brain involved in sleep, smell, and bladder control.

As Parkinson's advances, it affects the motor areas of the brain, producing symptoms such as tremors, rigid muscles, and problems with walking or posture.

Someone who is acting out their dreams at night often first learns they're doing this from their sleep partner. Sleep talking or sleep walking is usually something quite different from RBD, points out Postuma.

A specialist at a sleep clinic can confirm the diagnosis. Postuma also recommends that RBD patients should be followed by a neurologist, who can monitor and treat their symptoms should any Parkinson changes emerge. 

Want more weird health news? Find The Body Odd on Facebook.

Having wrinkles adds well, a new wrinkle for young people trying to gauge the emotions seen on older people's faces. A new study suggests that younger people may make more mistakes when judging the emotions of older folks.

To younger adults, age-related changes, such as wrinkles and folds, look like facial expressions, so they may interfere with the perception of emotion in an older face and perhaps convey the wrong message.

In the study, published online in the Journal of Experimental Social Psychology, researchers asked 65 college students to view computer-generated black and white faces. They viewed faces of three men and three women who were young (ages 19 to 21) or old (ages 76 to 83) displaying one of four facial expressions: neutral, happy, sad, or angry.

Participants were asked to rate the emotional expression on the person's face on a scale from 1 for "not at all intense" to 7 for "very intense."

Young people were were most accurate in recognizing an angry expression and least accurate in judging sadness in old faces. They perceived happy faces in older people as showing less overall emotion than a younger person.

The study found that a facial expression, such as pure anger, on an older face is perceived differently -- and less clearly -- than the very same expression displayed on a younger person.

"In the case of the older expresser, the anger is seen as mixed with other emotions,"  says lead author Dr. Ursula Hess, a professor of psychology at Humboldt-University in Berlin, Germany.  "Clearly it makes a difference whether you think someone is just angry or someone is both angry and sad," she adds.

Even when it came to a neutral face, volunteers perceived that there was more emotion in a neutral older face than in a younger one.

Courtesy of Dr. Ursula Hess

Here's an example of the images researchers used in the study.

Researchers suggest that wrinkles do impact the communication of emotion.

"We may make mistakes when judging the emotions of the elderly," says Hess. "This may result in less harmonious interactions."

The age of the observers also likely made a difference in the results. Had the study participants been closer in age to the older faces, they would have had more experience at recognizing older faces to overcome the difficulties posed by a less clear emotional signal, Hess explains.

Although Botox may help smooth out the furrows and lines of an older face, it won't make it any easier for people to gauge your emotions. The cosmetic injections may limit facial expressions, making them harder to read.

So how can an older person make their emotions more visible -- and less obscure -- to other people?

Emotions are usually transmitted via a number of channels, including voice and posture, as well as the face, suggests Hess. And during everyday interactions, expressions are more dynamic than looking at a black-and-white photograph in a lab.

Since there are many different sources of emotion information, "an attentive interaction partner could learn how to properly decode the emotion," says Hess. That's probably why older people are better at decoding other older people's expressions.

Related:

• Is 'old person smell' real? Yes, but it's not what you think
• Happy deathday? You're more likely to die on your birthday
• What 25 years of driving a truck can do to your skin

Want more weird health news? Find The Body Odd on Facebook.

Crossing that bridge when you come to it is terrifying when you have a fear of bridges.

Known as gephyrophobia (pronounced jeff-i-ro-fo-bia), people with an intense fear of driving over a bridge -- or for some, the mere thought or anticipation of it -- brings on a panic attack. Their hearts race and palms sweat, and they may also have trouble breathing and feel light-headed.

If driving, their hands death-grip the steering wheel. They worry about losing control of the car and veering off the bridge, or of becoming so freaked out that they stop traffic with no shoulder of the road to pull into. 

Gephyrophobes are "not worried about the bridge collapsing, they're worried about themselves collapsing," says Jean Ratner, a social worker who directs the Center for Travel Anxiety in Bethesda, Md. She says a bridge phobia may stem from a fear of heights, and what's at the root of the problem is being scared of having a panic attack and not being able to manage it.

This anxiety disorder usually has a sudden onset and tends to strike extremely good drivers, suggests Ratner. It often catches a person by surprise because this was someone who previously had no trouble crossing bridges. Then one day, a panicky feeling occurs on a tall bridge, typically on the first half of it as the car is climbing up the arch.

Both the length and the height of the bridge can freak out sufferers, who may drive miles out of the way to find an alternative route or make excuses for their travel-related anxieties. A dread of bridges is more likely when the person is doing the driving, but may also occur as a passenger. 

Although less common than a fear of flying, bridge phobia is treatable in 6 to 9 months, suggests Ratner. She starts with office-based sessions to develop relaxation strategies that target the symptoms of panic, such as a slower breathing pattern and looking straight ahead. Then these behavioral methods might be practiced in a car on local roads.

Next Ratner might accompany that person while they walk across a bridge. Very gradually, the person works up to walking halfway across alone.

As a person slowly builds up more courage, then Ratner will discuss driving over a small bridge in a car with her sitting in the front seat. Then they may attempt a bigger bridge together. The next session may find Ratner in the back seat, then eventually to her in a separate car trailing behind the fearful driver.

Some people may take a mild tranquilizer to help them get over their bridge jitters, or carry it in a purse or wallet in case of panic.

Of the phobias she treats, Ratner says this is a hard one. With a fear of flying, people realize they're not piloting the plane. But with a fear of bridges, the driver is in charge and that person often feels an incredible sense of responsibility especially if other family members are depending on this individual to transport them safely.

Some bridges have drive-over services for the skittish. Nervous motorists can arrange to have someone else shuttle your car while you close your eyes or cower in the back seat. Some places charge for the service while others do it for free.

If drive-over services helps people get where they want to go, Ratner says she's very open them. But working with a therapist who treats phobias can be a bridge to getting over these fears for good.

Related:

• That weird urge to jump off a bridge, explain
• Some insomniacs may just be afraid of the dark
• Spiders look bigger to arachnophobes

Want more weird health news? Find The Body Odd on Facebook.

You've heard about the elephant in the room, which no one wants to talk about. Now new research describes a gorilla in the room, which not everyone seems to hear.

For the first time, a study has confirmed the existence of "inattentional deafness." This is "when the absence of attention causes people to miss sounds that are otherwise easily detectable," says study author Dr. Polly Dalton, a senior lecturer in cognitive psychology at Royal Holloway, University of London.

In this study, appearing online in the journal Cognition, Dalton and co-author Nick Fraenkel asked 45 people aged 16 to 47 to listen to a recording on headphones. Half of the participants were told to pay attention to the two women talking in the recording, while the others were told to tune in to a conversation between two men.

Halfway through the recording, a man's voice is heard repeatedly saying "I'm a gorilla" for 19 seconds.

Participants were later asked if they heard anything unusual. To hear what the audio sounded like, click here. 

While 10 percent of the people listening to the men's voices failed to detect the "gorilla," 70 percent of the volunteers listening to the women's voices didn't hear it.

Afterward when researchers explained the study, "most of our participants found it hard to believe that they had missed such an unusual and distinctive sound, particularly given that it lasted for 19 seconds," says Dalton.

The research was modeled after a classic psychology study of "inattentional blindness."

This "invisible gorilla" study found that when people were focused on a visual task -- watching a video and counting the number of basketball passes made by one team --  they failed to notice someone walking across a basketball court dressed in a gorilla suit.

Dalton and Fraenkel monkeyed around with this concept replacing the visible gorilla with an auditory one to see if it would also go undetected.

In a second version of the experiment with 50 different volunteers, the male voice saying "I'm a gorilla" walked closer to the two women talking.

There was even more "inattentional deafness" in this scenario because 35 percent of participants focused on the men's conversation failed to hear the "gorilla" and 55 percent of volunteers concentrating on the women's discussion missed it.

"I think the most surprising aspect of the findings was just how strong the effects of attention could be," points out Dalton. When attention is lacking, it can leave people "deaf" to sounds or "blind" to visual images they would otherwise hear or see. 

One real-life example of inattentional deafness is when you're sitting in a restaurant with a friend, and two people are having an interesting conversation at a nearby table. But you've completely missed everything your friend has been saying to you because you've been listening in -- eavesdropping, really -- to the others' talk. 

Dalton suspects inattentional deafness happens because the brain is prioritizing the signals when concentrating on one task, but it filters out irrelevant information to avoid being distracted.

But don't go blaming inattentional deafness the next time you hear the words "Please, take out the garbage." That's usually a deliberate failure between your ears known as selective hearing, or only hearing what you want to hear.

Want more weird health news? Find The Body Odd on Facebook.