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In the classic movie White Christmas, Bing Crosby jokingly tells Rosemary Clooney that by eating the right sandwich before bed, he can make sure he dreams about redheads, or blondes. If only we could all influence the content of our dreams so easily.

Well, a dream researcher in Hong Kong named Calvin Kai-Ching Yu, of Shue Yan University, says we can, at least a little.

For a study released last week in the journal Dreaming, he sampled 670 people, mostly university students, two-thirds of whom were females. He had them complete surveys about the intensities of their dreams, how often their dreams contained specific themes (such as flying, being chased, suffocation, and so on), and personality traits. They also indicated how often they slept on their sides, face up (supine), or face down (prone) on a five point scale from “never” to “almost every time.”

When he analyzed the numbers, he found that the prone sleepers, as a group, were much more likely to score highly on what he calls the Dream Motif Scale (DMS), regardless of their personality type. Motifs like “persecution,” “erotomania,” and “sex” appeared significantly more frequently.

He concluded that “this study provides the evidence that dream experiences, and in particular dream content, can be influenced by body posture during sleep.”

In other words, sleeping face down is more likely to give you intense dreams featuring several common themes. Among the persecution motifs, for example, people reported “being tied up,” “being locked up,” and “unable to move.”

But why would position so influence the content of our dreams? Kai-Ching Yu believes that the prone position provides more intense physical stimulus, making it tougher to breathe, for example, and making our bodies feel more constricted.

“The unconscious brains of the dreamers try to make sense, and even make use of, the external stimuli,” he told NBCNews.com.

It’s something like the dreams we have – common across cultures – when we have to urinate. We’re sleeping, but the pressure begins influencing our dream content so we start dreaming about bathrooms, or having to go. Also, when we’re face down, our genitals are receiving more stimulus from the bed and sheets, he speculates, so our brains incorporate that into sex-related dreaming.

He may be right, but there are reasons to be skeptical. First, a common problem in dream research is that people often don’t accurately recall their dreams even when they’ve just awakened. Also, while many people may think they know what position they sleep in, they’re often wrong. The dream scales Kai-Ching Yu used in his study were invented by him and, he said, they have not been validated by other researchers, though he has used them in many studies and gotten consistent results.

But the biggest reason for skepticism is that other scientists argue we’re cut off from the external world when we’re asleep. We’re in a completely internal realm – at the mercy of what sleep researchers from Harvard have called “a virtual reality system” without meaningful responses to the outside world, like the touch of sheets or the pressure of our bodies laying face down.

He doesn’t completely disagree, but said “I believe that the brain during sleep is not at all totally detached from the external world, and somatosensory stimuli, including those stemming from the environment, are probably incorporated into dream content more often than people observe or are aware of.” This is especially true, he thinks, at the unconscious level. That’s where our brains try to make sense, even if distorted, of what the body’s feeling.

Brian Alexander (www.BrianRAlexander.com) is co-author, with Larry Young PhD., of "The Chemistry Between Us: Love, Sex and the Science of Attraction," (www.TheChemistryBetweenUs.com) to be published Sept. 13.

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Sitting at your desk, a muscle in your leg palpitates quickly. Or a muscle under your eye flutters. These sudden twitches, known as fasciculation, occur commonly and seem random.

But are these spasms simply minor annoyances? Or are they signs of something more. 

“[A fasciculation] is small and it involves one muscle and it is a local problem,” explains Dr. Jagan Pillai, a neurologist for the Center for Brain Health at Cleveland Clinic.

Fasciculation occurs when a muscle spontaneously becomes excited because of nerve miscommunication. Motor neurons, which live in the spinal cord and base of the brain, send their axons out to tell muscles how to move, but in some situations a disruption occurs, causing fasciculation. Exhaustion, anxiety or depression, nicotine, or too much caffeine can make nerves hyper-excited, disrupting the motor neurons and causing a muscle to flutter wildly.

“Fasciculation is a twitching in the muscles because of abnormal firing of the nerves,” says Dr. Kourosh Rezania, an assistant professor of neurology at the University of Chicago Medical Center.

 “Very often it’s of unclear significance and doesn’t lead to any long term problems.”

Because physicians believe things such as stress and exhaustion cause fasciculation, most solutions are at-home remedies.  

“If [muscle twitches] are really bothersome, the best thing to do is lifestyle modification; get plenty of sleep, exercise, relaxation, and minimize caffeine [consumption],” says Dr. Carlayne Jackson, a professor of neurology at the University of Texas Health Science Center, San Antonio and a member of the American Academy of Neurology.

While the majority of muscle twitches are harmless, fasciculation can be a symptom of other disorders, ranging from very serious to mild. Fasciculation occurring with muscle weakness and atrophy can be a sign ALS, also known as Lou Gehrig’s disease. 

“If [patients] have fasciculation and no weakness, it is unlikely it will have an ominous outcome,” explains Jackson.  

Having frequent fasciculation does not mean that one will develop ALS or any other disease. People with ALS complain more of muscle weakness and pain, Rezania says. 

A less serious, rare condition—known as cramp fasciculation syndrome—causes cramps, pain, fasciculation, and fatigue.

“Cramp fasciculation symptom does not become ALS,” stresses Rezania. “The nerves are excitable and that causes increased symptoms.”

Pillai notes that if patients complain of jerks in their body, doctors must determine the cause of fasciculation—twitches can also be related to diseases such as MS, epilepsy, thyroid disease, or kidney disease, but these disorders almost always have other symptoms associated with them. And physicians must diagnosis whether the movements are fasciculation or myoclonus, which are sudden, involuntary muscle twitches, impacting a group of muscles. Hiccups and hypnic jerks are both forms of myoclonus.  

“[Fasciculation] is commonly noted in normal people, but it could be a sign of a neurological problem. If it is persisting for a long time, it should be taken more seriously than [a twitch] that lasts for a few minutes or an hour,” Pillai says.

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People suffering from motor neuron diseases, such as ALS, often lose their ability to speak. Being unable to communicate can be frustrating and alienating. To help them, various researchers have searched for ways to help such patients “talk.”

A researcher in France taught people to write with their eyes, making it possible for people who lost the ability to speak to communicate again.  

Jean Lorenceau, director of research in cognitive neuroscience at CNRS (the French National Centre for Scientific Research), and six others learned how to use smooth pursuit eye movements to write in cursive. Smooth pursuit eye movements are those we use to track something as it moves, like watching a car drive down the street. These movements only occur if there is something for the eye to follow.

“We have an exquisite, fast, and accurate oculomotor system that has a whole repertoire of movements,” says Lorenceau via email.

“Too bad that [the oculomotor system] is only used to see and cannot be used to act on the environment. Cursive writing is continuous, curved, and smooth, just as pursuit eye movements are, so [these] eye movements should be suitable for this activity.”

In anywhere from three to five, 30-minute training sessions (the faster the learner, the fewer training session), the subjects learned how to control their smooth eye muscle movements to write in cursive.

“We move the eyes all the time, so eye writing relies on a natural activity, although slightly unusual,” he says.

On a computer screen, Lorenceau projected a reverse phi-movement effect, an optical illusion where static objects look like they are moving, in the background as the object that the eye tracks. This allowed them to learn how to independently move their eyes using smooth pursuit eye movements.

"[The paper] presents a novel and highly innovative new technique for gaze-controlled cursive writing," explains Miriam Spering, an assistant professor in the department of ophthalmology and visual sciences perception and action at the University of British Columbia."The type of eye movement used here are so-called smooth pursuit eye movements--the eyes' main response to moving visual stimuli. Until [Lorenceau's] contribution, it was widely believed that this type of eye movement could not be controlled at will."

Lorenceau recorded the subjects, using an eye tracker, a video camera connected to a computer. As the camera films the movement in one eye, a software program tracks the position of the pupil over time and Lorenceau collects all the recorded movements and compiles them, making the letters.

While learning how to move their eyes—which Lorenceau says is similar to learning how to surf and stay on a wave—the subjects experienced frustration because they could not initially force their eyes to move how they wanted. Users cannot see what they are writing with their eyes; it can be tiring and confusing at times.

While others have designed systems that enable people to communicate with their eyes by blinking to select a letters from a screen or to surf the web, Lorenceau’s method offers something more.

“My device brings personal, creative, and emotional ways of communication, for instance the ability to sign a document using one’s signature,” he explains.

Lorenceau plans on testing this technology with people with ALS. And he is working with a French technology company to create other applications of this system so that it might be easier for people to access.  

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When Lauren Kornacki discovered her father crushed beneath his BMW 525i,  which had slipped off the carjack as he was working on it, the 22-year-old wedged herself under the mid-sized vehicle -- and pulled it off her father.

We hear tales from time to time of people exhibiting superhuman strength in life-and-death emergencies. After experiencing amazement over such a feat, we all wonder: How can a regular person lift something that weighs more than a ton?

Actually, most people "can lift six to seven times their body weight," says Michael Regnier, professor and vice chair of bioengineering at the University of Washington. But most people don’t push themselves so hard, though athletes often push themselves more than most. Fear, fatigue and pain prevent people from attempting feats of amazing strength in daily life, says Dr. Javier Provencio, director of the neurological ICU at Cleveland Clinic.

Regnier, a former world-class weightlifter, has experienced bouts of incredible strength both as an athlete and as someone who helped after an accident. About 20 years ago, Regnier was driving on a Los Angeles freeway when he spotted a wrecked car on the side of the road. The driver sat slumped over his steering wheel so Regnier pulled over to help. It was instinct; he couldn’t fathom leaving the man without doing something. The driver’s door had caved in and Regnier couldn’t get him out any other way—he ripped the door off to pull the man out.

Regnier remembers his hands hurting from cuts he sustained while tearing off the car door, but he doesn’t know what happened with the driver because he left when the EMTs arrived.

Ripping doors off cars or lifting vehicles from people could be considered hysterical strength. Little medical evidence exists about such cases; most of it remains anecdotal.    

Physicians once believed that the adrenaline that flooded the system caused an extra boost to the muscles, allowing people to be stronger. But that’s not quite accurate. Adrenaline certainly primes the body for emergency action, it speeds up the heart and lungs, dilates the blood vessels and releases nutrients, both of which ready the muscles for quick responses.  

And while the adrenaline fueled fight-or-flight reflex spurs people into action, the body’s entire stress response contributes to superhuman strength. Cascades of enzymes and proteins release, helping people sustain the activity.

“Endorphins are very important,” says Provencio. Our bodies release endorphins when we exercise, providing that “runner’s high.” 

These neuropeptides make people feel good and suppress pain as well as providing people with an extra boost to finish their superhuman task.

“[Endorphins] sort of make the brain available to handle these stressful situations. You focus on the task you are doing,” says Regnier. “The endorphins will have a longer lasting affect.” 

While the body’s stress response enables humans to turn into less angry Incredible Hulks, our emotions truly motivate people to attempt such actions.  In most cases, the rescuers believe the victim will die without help. Take 21-year-old Danous Estenor, a University of South Florida football player, who lifted a car off a 34-year-old tow truck driver pinned under a tire in 2011. He believed Pedro Arzola would have perished without his intervention.

“The people who do these things are really under a lot of stress,” says Provencio. “It really touches them personally.” 

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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."

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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.

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It’s nearing 1 a.m. The lights are dim in the bar and the opening riffs of Queen’s “We are the Champions” blare from the stereo. Suddenly, it seems like everyone in the bar is singing, “We are the champions, my friends, and we’ll keep on fighting, till the end …” 

“I was out on a night out and I saw [several] groups sort of huddled together belting out songs at the top of their lungs. And I was blown away by the all enthusiasm and vigor,” says Alisun Pawley, a musicologist and lecturer at Kendal College in England.

“It had a tribal quality. What is it about this song?” 

To understand why people croon in bars, Pawley visited pubs and clubs in several towns in Northern England. Over 30 days, she recorded 1,110 songs, played throughout the evening. In addition to capturing the song, she noted what lyrics roused the crowd and estimated the number of people singing when the tune reached its climax. 

She and a colleague, Daniel Müllensiefen, a music psychologist at Goldsmiths, University of London, analyzed the most popular songs to see if they shared any particular similarities. 

Paul McCartney leads athletes and audience members in what amounted to one massive sing-a-long to the Beatles song

“We looked at various aspects from their melodic aspects, the range, the intervals between notes -- I thought that maybe if [the intervals] weren’t as far apart it would be easier to sing, [but] that wasn’t influential,” she says. “We looked at the aspect of the lyrics and how relevant they were in the context of a pub.”

Pawley found that pub-goers most enjoyed crooning high-energy songs sung by male vocalists with high chest voices and fewer warbles (these qualities describe something known as an anthemic vocal performance). All the popular songs spent at least four weeks on the UK music charts. Crowds that engaged in sing-a-longs were normally younger and the later it was, the more likely it was they would sing.      

“The later on in the evening, the more people sang along and we largely relate that to alcohol,” she says. 

While Pawley thought that songs with nonsense words such as “Hey Jude,” with its "nah, nah, nah, nah" would be more popular, she found nonsense words didn’t add a song’s appeal. (“Hey Jude” united the world in a sing-a-long during the opening ceremony of the 2012 London Olympics, which Pawley says was “just brilliant.” She believes the song was a hit with an international crowd because non-English speakers don’t need to understand nah to enjoy it.)

People gravitated toward songs with some cultural significance. Even if “YMCA” isn’t on a personal favorite, people know the words and it’s a mainstay at festive events.

“Songs have kind of a tradition about them and very new songs haven’t necessarily built a culture.”

She hopes to conduct similar research in the United States. She suspects the songs might have different titles, but will share the same musical properties. 

The article will be published in the journal Music Perception later this year.

Top 10 pub songs in England:

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