Dreaming is a form of mental activity, different from waking thought, that occurs
during sleep. The nature of dream activity has been characterized by many
clinical and laboratory studies. These studies show that dreams are more
perceptual than conceptual: Things are seen and heard rather than thought. In
terms of the senses, visual experience is present in almost all dreams; auditory
experience in 40 to 50 percent; and touch, taste, smell, and pain in a relatively
small percentage. A considerable amount of emotion is commonly
present—usually a single, stark emotion such as fear, anger, or joy rather than
the modulated emotions that occur in the waking state. Most dreams are in the
form of interrupted stories, made up partly of memories, with frequent shifts of
This broad characterization includes a great variety of dream experiences.
Many dreams collected in sleep laboratories are rather ordinary, but most people
have at least some bizarre dreams. At the start of the 20th century Sigmund
Freud proposed that a mental process quite different from that used in the waking
state dominates the dreaming mind. He described this “primary process” as
characterized by more primitive mechanisms, by rapid shifts in energy and
emotions, and by a good deal of sexual and aggressive content derived from
Research in recent years has clarified many of these aspects of dreaming,
but what may be of greatest significance has been the discovery of a biology of
dreaming. Starting with the work of American sleep researchers Eugene
Aserinsky and Nathaniel Kleitman in 1953, studies have shown that a dream
does not consist of fleeting imagery that occurs while a person awakens from
sleep, but instead a dream takes place during a biological state of its own.
Thus, two clearly distinguishable states of sleep exist. The first state,
called S-synchronized sleep, or NREM-sleep, occupies most of the sleep period
and is associated with a relatively low pulse and blood pressure, little activation
of the autonomic nervous system, and few or no reports of dreaming. The second
type of sleep, known as D-sleep, or REM-sleep, occurs cyclically during the
sleep period and is characterized by activation of the autonomic nervous system,
rapid eye movements, and frequent dream reports. Typically, a person has four
or five periods of D-sleep during the night, whether the dreams are remembered
often, rarely, or not at all; they occur at intervals of about 90 minutes and
altogether constitute about 25 percent of the night’s sleep. Evidence indicates
that a dream period usually lasts from 5 to 20 minutes.
Such stimuli as sounds and touches impinging on a dreamer can be
incorporated into a dream if they occur during a D-period. These stimuli,
however, do not initiate a D-period if one is not already in progress, so that, at
least in such cases, dreams do not protect sleep in the way that Freud suggested.
Although mental activity may be reported during NREM-sleep, these are usually
short, fragmented, thoughtlike experiences.
Ancient cultures believed that dreams were spiritual in origin, often
foretelling the future. Aristotle believed that dreams originated from within the
dreamer, arising from the heart. Modern dream research has focused on two
general interpretations of dream content. In one view, dreams have no inherent
meaning but are simply a process by which the brain integrates new information
into memories. In the other view, dreams contain real meaning symbolized in a
picture language that is distinct from conscious logical thought.
The recounting of dreams has been used widely as part of clinical
treatment. If dreams express important wishes, fears, concerns, and worries of
the dreamer, the study and analysis of dreams can help reveal previously
unknown aspects of a person’s mental functioning.

Category: Miscellaneous