Most people have several dreams each night, although they may not always remember them. The average person experiences four to six dreams per night. However, this number can change depending on various variables, including how well a person can recall their dreams and the amount of time spent in various stages of sleep. Dreams happen while a person is in the rapid eye movement (REM) stage of sleep, which usually accounts for 20–25% of an adult's total sleep time. People tend to have more vivid and memorable dreams at this time since the brain is quite active.