A sequence of imagery, thoughts, and emotions that pass through the mind during sleep.

Dreams defy the laws of physics, the principles of logic, and personal morality, and may reflect personal desires as well as fears and frustrations. They often occur in story-form with the dreamer as a participant or observer and may involve several known or unknown characters, motion, and various activities. Sensations of taste, smell, hearing, or pain may be present. The content of dreams clearly reflects daytime activities and locations from the dreamer's life, even though these may be distorted to various degrees. While some people report dreaming only in black and white, others dream in color. Lucid dreaming, in which the sleeper is actually aware of dreaming while the dream is taking place are not uncommon.

Research has indicated that everyone dreams during every night of normal sleep. Many people do not remember their dreams, however, and most people recall only the last dream prior to awakening. The memory shut-down theory suggests that memory may be one of the functions of the brain that rest during dreaming, hence people forget their dreams.


Continuity principle—
In psychology, the perceptual organization that individuals use to group stimuli into continuous patterns.
Existential analysis—
Analysis of dreams based on the feelings of the dreamer, contents of dreams, and the dreamer's response.
Refers to the development of the individual and the process within society that differentiates one person from another.
Phallic symbol—
Any object that may broadly resemble or represent the penis, most often as a symbol of power.
An act or instance of symbolizing or representing something; the human capacity to develop a system of meaningful symbols.

To help understand how dreaming occurs, researchers have measured brain waves during sleep using electroencephalography (EEG), a noninvasive method of recording electrical activity of the brain along the scalp. An electroencephalogram shows the measurement of brain waves over time and is typically used to evaluate brain disorders. Brain waves measured during sleep are normally large and slow but become smaller and faster during periods of sleep accompanied by rapid eye movements (REM or REM sleep). Dreams typically occur during these periods of sleep. During a normal eight-hour period of sleep, an average adult dreams three to five dreams lasting 10 to 30 minutes each for a total of 100 minutes.

After Freud, psychologists and psychotherapists used dream interpretation to gain abundant information about the structure, dynamics, and development of the human personality. Several theories attempted to explain why people dream. The Swiss psychologist Carl Jung (1875–1961) applied a different form of analysis than Freud but agreed with Freud's basic view of dreams as compensating for repressed psychic elements. According to Jung, significant dreams that involve the collective unconscious are attempts to reveal an image, or archetype, that is not sufficiently individuated in the subject's personality. The Swiss analyst, Medard Boss (1903–1990), offered another system of existential analysis in which the significance of dreams lay close to their surface details rather than corresponding to an intricate symbolic pattern. For example, dreams set in a narrow, constricted room may indicate the way the dreamer views his or her existence. Existential analysis is based on the feelings of the dreamer, the contents of the dream, and the dreamer's response to them.

Modern researchers gather data from subjects in a sleep laboratory, a mode of investigation furthered in the 1950s. Calvin Hall (1909–1985), a pioneer in the content analysis of dreams, suggested that dreams are meant to reveal rather than to conceal. Hall and his colleagues gathered dreams from a large and varied sampling of subjects and analyzed them for the following content categories: (1) human characters classified by sex, age, family members, friends and acquaintances, and strangers; (2) animals; (3) types of interactions among characters, such as aggressive or friendly; (4) positive and negative events; (5) success and failure; (6) indoor and outdoor settings; (7) objects; and (8) emotions. Other investigators devised their own systems of content analysis, such as the one outlined by David Foulkes in A Grammar of Dreams. The dreams of children have also been assessed extensively through laboratory testing and have been shown to be linked to their cognitive development. Content analysis has also yielded longitudinal information about individuals, including the observations that an adult's dreams remain strikingly similar over time and are strongly linked to the preoccupations of waking life, a phenomenon known as the continuity principle.

Dream analysis may be included in certain therapies. In the 1970s, writers and psychologists helped to popularize dream analysis by offering techniques individuals can use to analyze their own dreams. Widely recommended techniques include keeping paper and pen by the bed to write dreams down upon waking, even in the middle of the night. Keeping a dream diary is also recommended in order to recognize recurring themes and make associations with the imagery in the dream to decode its personal meaning. Analysts maintain that dreams contain the dreamer's thoughts or feelings not yet expressed or made conscious, and if the dreamer can make associations to the dream, it may reveal ways the dream mirrors inner tensions or desires in the dreamer's emotional life. The dreamer can then uses the associations to interpret or give meaning to the dream. Some psychologists recommend cultivating lucid dreaming in which dreamers are aware in the dream that they are dreaming and can direct the events of dreams and the manner in which they unfold.

Some scientists have attempted to discount the significance of dreams entirely. The activation-synthesis hypothesis created by J. Alan Hobson (1933–) and Robert W. McCarley (1937–) in 1977 holds that dreaming is a simple and unimportant by-product of random stimulation of brain cells activated during REM sleep. Another dream theory, the mental housecleaning hypothesis, suggests that people dream to rid their brains of useless, bizarre, or redundant information. A variation of this theory sees dreaming as analogous to a computer's process of program inspection in which sleep is similar to downtime and the dream becomes a moment of online time, a glimpse into a program being run at that moment.

Research is ongoing on the source and meaning of dreams, including studies of neural networks of the brain, cognitive development, and dream content analysis. Advances in neuroscience and computer software have helped to revitalize dream research using scientific methods rather than depending exclusively on the hypotheses of individual dream analysts. Although dream content can be based in part on waking cognition and personal concerns, research still shows that there are many other aspects of dreams that are not yet understood. The American Psychological Association reports that new systems of content analysis have been devised that apply highly sophisticated studies to help investigate why people dream and what dreams mean.

See also Rapid eye movement (REM).



Domhoff, G. William. The Scientific Study of Dreams: Neural networks, cognitive development, and content. Washington, DC: American Psychological Association, 2003.

Freud, Sigmund. The Interpretation of Dreams: The Complete and Definitive Text. New York: Basic Books (Trade Edition) & Leventhal, 2010.


Domhoff, G. William. “Dream Content Is Continuous with Waking Thought, Based on Preoccupations, Concerns, and Interests.” Sleep Medicine Clinics 5, no. 2 (June 2010): 203–15.

Lee, Raymond L. M. “When Is Dreaming Waking? Continuity, Lucidity, and Transcendence in Modern Contexts of Dreaming.” International Journal of Dream Research 8, no. 1 (April 2015): 66–71.

Zink, Nicolas, and Reinhard Pietrowsky. “Theories of Dreaming and Lucid Dreaming: An Integrative

Review towards Sleep, Dreaming and Consciousness.” International Journal of Dream Research 8 (April 2015): 35–53.


National Sleep Foundation. Dreams and Sleep. http://www.sleepfoundation.org/sleep-topics/dream-and-sleep (accessed July 24, 2015).