Side. Stomach. Back. Fetal: Most people have a preferred sleeping position. But can the way you get shut-eye say something about your personality?
But some experts say there is little evidence to back up the claims. And as it turns out, the recently cited "research" is actually a survey -- conducted by a hotel chain -- about the most common sleep positions.
Robert Phipps, a U.K.-based body language specialist, then gave an analysis he says was akin to a horoscope.
"Yes, it was never meant to be taken seriously and there was no research on my part," Phipps told The Huffington Post in an email.
The analysis in question linked sleep positions with different personality characteristics. As the Telegraph reported:
People who sleep in the fetal position are "worriers." (The tighter they curl up, the more comfort they're supposedly seeking.) Those who sleep on their stomachs, with their arms stretched are "free fallers. (They reportedly feel their lives are out of their control.) "Yearners" -- those who sleep on their sides, with their arms outstretched -- have a dream-chasing nature about them. And "Logs," those who sleep straight, have rigid personalities.
Despite the idea of a "sleep-o-scope" sounding somewhat far-fetched, this isn't first time personality types and sleep positions have been linked.
According to Dr. Chris Idzikowski of the Edinburgh Sleep Centre, in the 1940s, there was an article by a psychiatrist who claimed side-sleepers lacked moral fiber. The article prompted Idzikowski's decision to research whether there was any link between personality traits and sleep position, he told HuffPost in an email.
Idzikowski surveyed 1,004 British subjects about their preferred sleeping positions and asked them to check boxes with adjectives they felt described their personalities. Through factor analysis of the data, Idzikowski found an association between certain sleep positions and certain psychological traits.
The BBC reported on the results in 2003: Those who sleep in fetal position were said to be tough on the outside but sensitive on the inside, for example. "Log" sleepers were found to be easy-going and social. "Yearners" were open, cynical and slow to make up their minds. "Free fallers" were outgoing but thin-skinned and did not like criticism.
Still, Idzikowski's research relied on self-evaluations, and he said that when the survey was conducted among a group of Southeast Asians, the archetypes no longer held up.
Philip Gehrman, a professor of psychiatry and a member of the Penn Sleep Center, expressed doubts over whether there's deep meaning behind how people sleep.
"You can't argue with the fact that they did in fact find a correlation between sleeping position and personality," Gehrman told HuffPost. "[But] the link between sleeping [position] and personality is unlikely to be anywhere near strong enough to make those kinds of statements."
So what does influence the way people sleep? According to Gehrman, it's simply personal preference.
"It's really just a matter [of whether] you are comfortable," he said.
According to Dr. Stuart Quan, a professor of sleep medicine at Harvard Medical School, it would be difficult for people to have their personalities tied to one sleep position, because most people move around in their sleep.
"They will toss and turn. They're naturally switching positions," Quan said. "People who say 'I only sleep on my side, my left side,' they tend to move."
On the other hand, correlations between sleep positions and quality of sleep can exist, according to Quan, but such ties are likely the result of pre-existing health conditions.
Sleep apnea, for example, a disorder in which people experience irregular breathing during sleep, can be made worse by sleeping on one's back, Quan said. Heartburn, too, is another condition that could be made worse by the position a person sleeps.
What can influence the quality of sleep, according to Quan, is what people do while they are awake.
"Nicotine is a stimulant. If you exercise right before you go to sleep, you tend to be hyped," Quan explained. "Even if you get into an argument with your partner and then you try to go to sleep, those are obviously things that affect people trying to go to sleep."
Caffeine, medications and exposure to certain light -- like that of a laptop -- can all sabotage the potential for a good night's sleep. As a result, Quan discourages people from checking emails or watching television right before bed.
"We tell people the bedroom is for two things and they both start with S," said Quan. "The other things should be omitted and should be done somewhere else."
Can't sleep? Michael Decker, Michael Decker, Ph.D., an associate professor at Georgia State University and spokesperson for the American Academy of Sleep Medicine, breaks down which old-fashioned remedies really work.