Dreams can be fascinating, exciting, terrifying, or just plain weird. While there is no clear consensus on why we dream, researchers have learned quite a bit about what happens while we are dreaming. Here are 10 things you should know about dreams.

facts about dreams — Illustration by Brianna Gilmartin, Verywell

Everybody Dreams

Adults and babies alike dream for around two hours per night—even those of us who claim not to. In fact, researchers have found that people usually have several dreams each night, each one typically lasting for between five to 20 minutes.

During a typical lifetime, people spend an average of six years dreaming.

You Forget Most of Your Dreams

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7 Theories on Why We Dream Simplified

As much as 95 percent of all dreams are quickly forgotten shortly after waking. According to one theory about why dreams so difficult to remember, the changes in the brain that occur during sleep do not support the information processing and storage needed for memory formation to take place.

Brain scans of sleeping individuals have shown that the frontal lobes—the area that plays a key role in memory formation—are inactive during rapid eye movement (REM) sleep, the stage in which dreaming occurs.

Not All Dreams Are in Color

While most people report dreaming in color, there is a small percentage of people who claim to only dream in black and white. In studies where dreamers have been awakened and asked to select colors from a chart that match those in their dreams, soft pastel colors are those most frequently chosen.

Men and Women Dream Differently

Researchers have found some differences between men and women when it comes to the content of their dreams. In several studies, men reported dreaming about weapons significantly more often than women did, while women dreamed about references to clothing more often than men.

Another study showed that men's dreams tend to have more aggressive content and physical activity, while women's dreams contain more rejection and exclusion, as well as more conversation than physical activity.

Women tend to have slightly longer dreams that feature more characters. When it comes to the characters that typically appear in dreams, men dream about other men twice as often as they do about women, while women tend to dream about both sexes equally.

Animals Probably Dream

Many think that when a sleeping dog wags its tail or moves its legs, it is dreaming. While it's hard to say for sure whether this is truly the case, researchers believe that it's likely that animals do indeed dream.

Just like humans, animals go through sleep stages that include cycles of REM and non-REM sleep.

It's Possible to Control Your Dreams

A lucid dream is one in which you are aware that you are dreaming even though you're still asleep. Lucid dreaming is thought to be a combination state of both consciousness and REM sleep, during which you can often direct or control the dream content.

Approximately half of all people can remember experiencing at least one instance of lucid dreaming, and some individuals are able to have lucid dreams quite frequently.

Negative Emotions Are More Common

Over a period of more than 40 years, researcher Calvin S. Hall, PhD, collected over 50,000 dream accounts from college students. These reports were made available to the public during the 1990s by Hall's student William Domhoff.

The dream accounts revealed that many emotions are experienced during dreams.

The most common emotion experienced in dreams are anxiety, and negative emotions, and in general, are much more common than positive ones.

Blind People May Dream Visually

In one study of people who have been blind since birth, researchers found that they still seemed to experience visual imagery in their dreams, and they also had eye movements that correlated to visual dream recall.

Although their eye movements were fewer during REM than the sighted participants of the study, the blind participants reported the same dream sensations, including visual content.

You Are Paralyzed During Your Dreams

REM sleep is characterized by paralysis of the voluntary muscles. The phenomenon is known as REM atonia and prevents you from acting out your dreams while you're asleep. Basically, because motor neurons are not stimulated, your body does not move.

In some cases, this paralysis can even carry over into the waking state for as long as 10 minutes, a condition known as sleep paralysis.

While the experience can be frightening, experts advise that it is perfectly normal and should last only a few minutes before normal muscle control returns.

Many Dreams Are Universal

While dreams are often heavily influenced by our personal experiences, researchers have found that certain dream themes are very common across different cultures. For example, people from all over the world frequently dream about being chased, being attacked, or falling. Other common dream experiences include feeling frozen and unable to move, arriving late, flying, and being naked in public.