Yes. The average person has three or four dreams each night, with each dream lasting 10 minutes or more. Almost all dreams occur during REM sleep, a period of sleep characterized by fast breathing and heart rates. Scientists do not understand why dreaming is important, but one theory is that the brain is either cataloging the information it acquired during the day and discarding the data it does not want, or is creating scenarios to work through situations that may be causing emotional distress. Like sleep, most people who are deprived of dreams become disoriented, are unable to concentrate, and may even have hallucinations. Sometimes it is hard to remember our dreams because they are stored in our short-term memory.