What are dreams for? Some say dreams let us fulfill our wishes[1] , others that they help consolidate our memories or give our minds a cognitive warm-up for emotional tasks[2] in the day ahead.


But in fact, no one really knows the precise function of dreams. One thing's for sure, though: dreams are very, very strange things. Keep reading for six fascinating facts about dreams and dreaming...


Most dreams aren't very sweet. In fact, dreams tend to be pretty darn unpleasant. A 2008 study confirmed that our dream experiences are negatively biased[3] . Some studies suggest that we've evolved to dream about scary situations more than positive ones because that prepares us for survival in case we come across a threat in real life.


"If you missed a threat[4] , you were lunch," Dr. Ross Levin, a psychologist and sleep disorder specialist at Yeshiva University in New York City, told Reuters. "The 'default' dream is basically the bad dream."


Dreams can be a "warning sign" of health problems. Just because you have a nightmare doesn't mean something is wrong with you. But a recent study showed that nightmares are sometimes linked[5] to heart conditions and migraines.


Also, "any infection increases the amount of slow-wave sleep[6] we have, however, this delays the starting point of when we enter dreaming sleep, so dreaming sleep starts late, and can erupt into consciousness," Dr. Patrick McNamara, a neurologist from Boston University Medical School, told the International Business Times. "This leads to vivid dreams and strange hallucinations.”


'Wet dreams' affect women too. While it's easier to find evidence for men having orgasms during their dreams, women have them too. In a 1986 study of university students, 37 percent of women reported having had a nocturnal orgasm[7] .


Dreams paralyze you--but only temporarily. During rapid-eye movement (REM) sleep, our muscles become paralyzed[8] -- a good thing, since that keeps our bodies from acting out jumping, running, punching, etc. Research has shown that two powerful brain chemical systems[9] work together to paralyze skeletal muscles during REM sleep.


You see more than you hear. Dreams tend to be more visual than auditory[10] , and more auditory than stimulating to the touch, Dr. Robert Stickgold, director of sleep and cognition at Beth Israel Deaconess Medical Center and a Harvard Medical School professor, told The Huffington Post.


We all have them... every night. You may not always remember your dreams, but scientists say we all dream at some point during sleep. The only exception is if you're suffering a disease or brain disorder of some kind.


Craving some more dream facts? Check out a slideshow and "Talk Nerdy To Me" episode on why we dream below.




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  • You Can Use Them For Problem-Solving


    You’ve heard it before, and now it’s legit: Sleep on your problems to solve them. The catch? According to a recent study from the U.K.’s University of Lancaster, <a href="http://link.springer.com/article/10.3758%2Fs13421-012-0256-7">dreaming is only an advantage when it comes to solutions that require a Eureka-like flash of insight.</a> (For instance: What word can form a compound word with <i>canal</i>, <i>true</i> and <i>boat</i>?) During REM (rapid eye movement) sleep -- the eyeball-jerking stage when vivid dreams often occur -- the frontal cortex processes new information like the riddle above. As new experiences integrate with preexisting knowledge, memory networks are stimulated -- and as a result, form new, random and sometimes wacky connections between unrelated concepts. Later, we wake up, stretch, and -- we can’t explain <em>how</em> -- the brilliant and now-perfectly-obvious answer just comes to us. (One we couldn’t see when we were doggedly trying to get at, for instance, the word <i>love</i>.)




  • You Can Dream Up The Next Big Thing


    The automatic sewing machine, the computer-controlled anti-aircraft gun, Otto Loewi’s Nobel Prize-winning experiment on nerve impulses -- all came as concrete plans in a dream, says <a href="http://en.wikipedia.org/wiki/Deirdre_Barrett">Deirdre Barrett, a psychologist at Harvard University</a> and author of <i><a href="http://www.amazon.com/The-Committee-Sleep-Scientists-Solving/dp/0982869509">The Committee of Sleep</a></I>. So: How do you increase the chances that you'll have your own Nobel-worthy breakthrough? First, think of your problem right before you go to sleep, says Barrett. Conjure up an image of the problem you need to solve (your Mac’s frozen screen; your husband’s sad face). Then, whatever you do, <em>don’t move</em> when you wake up. (Even turning your head may displace the dream!) If you've had nonsensical dreams, think about whether the imagery or events could be a metaphor for something that relates in any way to the problem you're stuck on, says Barrett. In her weeklong study, 50 percent of the volunteers had a dream about their problem and 25 percent actually dreamt up a solution.




  • Why, Yes! You CAN Be In Fiji By Midnight Tonight


    You can try to control the content and stickiness of your dreams -- if you believe the many new smartphone apps that are available. A recent tool, <a href="http://sigmundapp.com/">Sigmund</a>, developed by Harvard and MIT graduate students, whisperingly repeats words that you pick out of a database (<em>beach, flying, mermaid, queen</em>) during your REM cycle (based on predictable sleep-wake times). Another app, <a href="http://www.dreamonapp.com/">Dream:ON</a>, uses the phone’s motion-detecting accelerometer to gauge when you’re in REM (you’ll be stick-still), at which point it kicks in with the sounds of your pre-programmed dream (walking in the woods, frolicking at the shore, whatever). No one’s saying app-influenced dreams are exactly like the movie “Inception” -- not yet, anyway.




  • Bigger Dreamers Have Tinier Waistlines


    We see headlines for the “Dream Diet” after finding this gem: The more time you dream each night, the less hungry you are for fats and carbs. <a href="http://ajpregu.physiology.org/content/303/9/R883.full.pdf+html">Volunteers in a study at St Luke’s Hospital ate prescribed meals for four days under various sleep conditions</a>, fasted for a day, and then ate as much of any food they craved on days six and seven. When they slept for only four hours per night, their metabolism slowed down and they consumed more foods of the pasta and chocolate-pudding variety. One culprit is less energy-regulating stage-2 sleep than usual. Another is fewer cycles of REM. Dreaming is calorically demanding -- and because REM cycles get longer and longer only after the six-hour mark, you burn off fewer calories (yet paradoxically crave more) when you wake up too soon. If we dream a lot about cake, we may not (as desperately) want to eat it too. (Try a banana instead: A preliminary study finds that<a href="http://www.dailymail.co.uk/news/article-2127013/Want-remember-dreams-Start-taking-vitamin-B-6-eat-lots-bananas.html"> vitamin B-6 boosts dream vividness and recall</a>.)




  • Your Night-Owl Habit Has A Downside


    Ninety percent of us have had a nightmare in the past year. But <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1479-8425.2011.00511.x/abstract">night owls (especially female ones) are likelier to be among the 2 to 6 percent who have bad dreams weekly</a>, finds a study at Yúzúncú Yil University in Turkey. Sleep patterns are one possible culprit: Staying up and waking up late throws off circadian rhythms. And while everyone’s level of cortisol rises in the morning, the stress hormone may invade night owls’ dreams more -- because it coincides with the REM cycle they’re having right before they wake up.




  • The Upside Of Nightmares, Part One


    The positive news: Nightmares can be good for your mental health. Stressed-out, sheet-dampening dreams actually lead us to a healthier state of mind when we’re awake, finds psychologist Rosalind Cartwright from Rush University. When she studied people undergoing serious stress -- a divorce -- she found a surprising paradox: <a href="http://www.researchgate.net/publication/232575402_Dreams_that_work_The_relation_of_dream_incorporation_to_adaptation_to_stressful_events">Depressed people often had dreams that were pleasurable</a> (also short and lacking in detail), while their better-adjusted, more resilient peers had those of the ruthless variety. (Importantly, the nightmares involved the ex.) On a subconscious level, dreaming about conflicts helps to resolve inner turmoil at the times when we need to most. This is how we work through our emotions. Oh, and incidentally, <a href="http://www.sciencedaily.com/releases/2009/01/090128104535.htm">women have more nightmares than men</a>.




  • The Upside Of Nightmares, Part Two


    <a href="http://www.ncbi.nlm.nih.gov/pubmed/18708267">Bad dreams during pregnancy</a> -- you know, the usual ones about birthing traumas and losing, hurting or rejecting the baby -- may actually result in a shorter labor, found researchers at the University of Messina in Italy. Eighty minutes, on average -- that’s how much faster women with nightmares gave birth, compared to those who had pleasant dreams. (<a href="http://www.ingentaconnect.com/content/klu/drem/2003/00000013/00000002/00463726?crawler=true">They also have a lower rate of postpartum depression.</a>)




  • You've Heard Of Jet Lag? Meet 'Dream Lag'


    You saw your ex on the street last Monday, so why is it that you’re dreaming about him now? A day’s events often come back to us in dreams that night -- but just as often, they show up a week later. It’s the <a href="http://www.ncbi.nlm.nih.gov/pubmed/20739193">“dream-lag effect”: During REM, the hippocampus takes five to seven days to transfer select memories to long-term storage in the neocortex</a>, found a study led by Mark Blagrove, director of the Sleep Lab at Swansea University. “Dream lag” is associated with more positive emotions about previous events -- which scientists chalk up to the way we reprocess memories in our dreams. This means that if you spot your ex today, next week’s dream will put him in a softer, kinder light than tonight’s.




  • The Best Sex Probably Isn’t In Your Dreams


    Most dreams are about conflict with others -- not sex with them -- says psychologist William Domhoff in his book <i><a href="http://www2.ucsc.edu/dreams/Library/fmid.html">Finding Meaning in Dreams</a></i>. Sex happens in only 4 percent of women’s dreams and 12 percent of men’s, Domhoff writes.