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The awareness of the sensations, thoughts, and feelings being experienced at a given moment.

Stage 1 sleep

The state of transition between wakefulness and sleep, characterized by relatively rapid, low-amplitude brain waves

Stage 2 sleep

A sleep deeper than that of stage 1, characterized by a slower, more regular wave pattern, along with momentary interruptions of "sleep spindles"

Stage 3 sleep

A sleep characterized by slow brain waves, with greater peaks and valleys in the wave pattern than in stage 2 sleep.

Stage 4 sleep

The deepest stage of sleep, during which we are least responsive to outside stimulation.

REM sleep

Sleep occupying 20 percent of an adult's sleeping time, characterized by increased heart rate, blood pressure, and breathing rate; erections; eye movements; and the experience of dreaming.

Unconscious wish fulfillment theory

Sigmund Freud's theory that dreams represent unconscious wishes that dreamers desire to see fulfilled.

Latent content of dreams

According to Freud, the "disguised" meanings of dreams, hidden by more obvious subjects.

Manifest content of dreams

According to Freud, the apparent story line of a dream

Dreams-for-survival theory

The theory suggesting that dreams permit information that is critical for our daily survival to be reconsidered and reprocessed during sleep.

Activation-synthesis theory

Hobson's theory that the brain produces random electrical energy during REM sleep that stimulates memories lodged in carious portions of the brain.

Circadian rhythms

Biological processes that occur regularly on approximately a 24-hour cycle


Fantasies that people construct while awake


A trancelike state of heightened susceptibility to the suggestions of others


A learned technique for refocusing attention that brings about an altered state of consciousness

Psychoactive drugs

Drugs that influence a person's emotions, perceptions, and behavior.

Addictive drugs

Drugs that produce a biological or psychological dependence in the user so that withdrawal from them leads to a craving for the drug that, in some cases, may be nearly irresistible.


Drugs that have an arousal effect on the central nervous system, causing a rise in heart rate, blood pressure, and muscular tension. (cocaine, amphetamines)


Drugs that slow down the nervous system (alcohol, barbiturates, Rohypnol)


Drugs that increase relaxation and relieve pain and anxiety. (Heroin, Morphine)


A drug that is capable of producing hallucinations, or changes in the perceptual process. (Marijuana, MDMA, LSD)

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