Not All Dreams Are in Color

Adults and babies alike dream for around two hours per night—even those of us who claim not to. 

Researchers have found that people usually have several dreams each night, each one typically lasting for between five to 20 minutes.

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.

• 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.

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. 

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.

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.

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.

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.