section_path: Functions/Dreaming
section_name: Dreaming
paragraph_text: Dreaming
  
  During sleep, especially REM sleep, humans tend to experience dreams. These are elusive and mostly unpredictable first-person experiences which seem logical and realistic to the dreamer while they are in progress, despite their frequently bizarre, irrational, and/or surreal qualities that become apparent when assessed after waking. Dreams often seamlessly incorporate concepts, situations, people, and objects within a person's mind that would not normally go together. They can include apparent sensations of all types, especially vision and movement.
  
  Dreams tend to rapidly fade from memory after waking. Some people choose to keep a dream journal, which they believe helps them build dream recall and facilitate the ability to experience lucid dreams.
  
  A lucid dream is a type of dream in which the dreamer becomes aware that they are dreaming while dreaming. In a preliminary study, dreamers were able to consciously communicate with experimenters via eye movements or facial muscle signals, and were able to comprehend complex questions and use working memory.
  
  People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that have been relegated to the unconscious mind, and he used dream interpretation in the form of psychoanalysis in attempting to uncover these desires.
  
  Counterintuitively, penile erections during sleep are not more frequent during sexual dreams than during other dreams. The parasympathetic nervous system experiences increased activity during REM sleep which may cause erection of the penis or clitoris. In males, 80% to 95% of REM sleep is normally accompanied by partial to full penile erection, while only about 12% of men's dreams contain sexual content.