States of Consciousness - Review the Knowledge You Need to Score High - 5 Steps to a 5 AP Psychology, 2014-2015 Edition

5 Steps to a 5 AP Psychology, 2014-2015 Edition (2013)

STEP 4. Review the Knowledge You Need to Score High

Chapter 9. States of Consciousness

IN THIS CHAPTER

Summary: While you are reading this book you may find yourself daydreaming as irrelevant thoughts surface, images of other situations come into view, and you create inner, private realities unconnected to this topic. Daydreams provide stimulation when your interest is flagging and let you experience positive emotions. Although we hope not, you may even doze off. If so, you are experiencing different states of consciousness. In the late 1800s, early structuralists like Wilhelm Wundt, followed by Edward Titchener, examined consciousness in order to learn about the structure of the mind, and functionalists like William James considered consciousness as essential for adapting to the environment. During the first half of the 1900s, behaviorists discounted and ignored consciousness. By the 1950s, cognitive psychologists returned to the examination of consciousness, especially the phenomenon of attention. Attention is a state of focused awareness. What you pay attention to is what you process into perceptions, thoughts, and experiences.

Consciousness is your awareness of the outside world and yourself, including your own mental processes, thoughts, feelings, and perceptions. Your consciousness is selective, subjective and unique to you, always changing, and central to your sense of self.

This chapter examines variations in consciousness, some which you commonly experience and others which you don’t.

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Key Ideas

image Levels of consciousness

image Sleep and dreams

image Sleep disorders

image Hypnosis

image Meditation

image Psychoactive drugs—Depressants, Narcotics, Stimulants, Hallucinogens


Levels of Consciousness

Although your current level of consciousness is basically limited to what is relevant to you and what you notice, other events can either become conscious or influence your conscious experience. Your preconscious is the level of consciousness that is outside of awareness but contains feelings and memories that you can easily bring into conscious awareness. For example, if asked what you ate for dinner last night, you could easily remember and tell. Your nonconscious is the level of consciousness devoted to processes completely inaccessible to conscious awareness, such as blood flow, filtering of blood by kidneys, secretion of hormones, and lower level processing of sensations, such as detecting edges, estimating size and distance of objects, recognizing patterns, etc. For psychoanalysts, also known as psychodynamic psychologists, the unconscious, sometimes called the subconscious, is the level of consciousness that includes often unacceptable feelings, wishes, and thoughts not directly available to conscious awareness. According to cognitive psychologists, the unconscious is the level of consciousness that processes information of which you are unaware. The unconscious operates whenever you feel or act without being aware of what’s influencing you, whether it’s a stimulus from the current situation or from your past. Don’t confuse the unconscious and unconsciousness. Unconsciousness is characterized by loss of responsiveness to the environment resulting from disease, trauma, or anesthesia. Consciousness enables you to analyze, compare, and interpret experiences, and allows you to integrate what you already know, what you perceive in the present, and what you anticipate. Consciousness can be altered by sleep, hypnosis, meditation, and drugs.

Sleep and Dreams

Your finely tuned “biological clock,” controlled by the hypothalamus, systematically regulates changes in your body temperature, blood pressure, pulse, blood sugar levels, hormonal levels, and activity levels over the course of about a day. In an environment devoid of environmental cues to the length of a day, your free-running biological clock cycles approximately every 25 hours, but in a typical environment with light during the day and dark at night, cycles of changes, circadian rhythms, recur approximately every 24 hours. The forebrain, reticular formation, and thalamus are involved in the changes in wakefulness, arousal, and attention. Your physiological fluctuations are reflected in changes in your energy level, mood, performance, wakefulness, and sleep. Jet lag and night-shift work involve disruptions of circadian rhythms.

Why do you sleep? Evolutionary psychologists say that humans evolved a unique waking–sleeping cycle as a result of natural selection that maximized our chances of survival. Sleep serves at least two restorative functions—one involved in protein synthesis throughout the body, the other involved in maintaining plasticity of neural connections essential for storing and retrieving memories, which enables you to put together new material from the day before with old material. This is sometimes called consolidation. Sleep deprivation makes you drowsy, unable to concentrate, and impairs your memory and immune system. Sleep time seems to decrease from about 16 to 18 hours for a newborn, to about 7 to 8 hours for an adult.

Sleep is a complex combination of states of consciousness, each with its own level of consciousness, awareness, responsiveness, and physiological arousal. The amount we sleep changes as we age. Electroencephalograms (EEGs) can be recorded with electrodes on the surface of the skull. EEGs have revealed that brain waves change in form systematically throughout the sleep cycle (see Figure 9.1). When you are awake, your EEG shows beta waves when you are alert and alpha waves when you are relaxed. As you fall asleep, you pass into a semiwakeful state of dreamlike awareness, known as the hypnagogic state; you feel relaxed, fail to respond to outside stimuli, and begin stage 1 sleep. EEGs of stage 1 sleep show theta waves, which are higher in amplitude and lower in frequency than alpha waves. As you pass into stage 2, your EEG shows high-frequency bursts of brain activity (called sleep spindles) and K complexes. As you fall more deeply asleep, your stage 3 sleep EEG shows some very high amplitude and very low-frequency delta waves. In stage 4, your deepest sleep stage, EEGs show mostly delta waves. During stage 4, your heart rate, respiration, temperature, and blood flow to your brain are reduced. You secrete growth hormone involved in maintaining your physiological functions. Stages 1 through 4, during which rapid eye movements do not occur, are called NREM or Non-REM sleep. After passing through stages 1 through 4, you pass back through stages 3, 2, and 1; then, rather than awaking, you begin REM sleep (Rapid Eye Movement sleep) about 90 minutes after falling asleep. Your eyes jerk rapidly in various directions; your breathing becomes more rapid, irregular, and shallow; your heart rate increases; your blood pressure rises; and your limb muscles become temporarily paralyzed. Because your EEG shows beta activity typical of wakefulness and theta activity typical of stage 1 sleep, but you are truly asleep, REM sleep is often also called paradoxical sleep. Throughout the night, you cycle through the sleep stages with REM sleep periods increasing in length and deep sleep decreasing. About 50% of our sleep is in stage 2. More of a newborn’s sleep is spent in REM sleep than an adult’s. Nightmares are frightening dreams that occur during REM sleep. Most of your dreaming takes place during REM sleep. Dreams remembered from other stages are less elaborate and emotional. Training in lucid dreaming, the ability to be aware of and direct one’s dreams, has been used to help people make recurrent nightmares less frightening.

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Figure 9.1 (a) Electroencephalograms of human sleep stages. (b) Sleep stages during a typical night.

“Remember delta and deep. Deep waves on the beach are high, so they have a high amplitude. Stages 3 and 4 are the highest numbers for sleep stages.”

—Lori, AP student

Interpretation of Dreams

But what do dreams mean? Psychoanalyst Sigmund Freud thought dreams were “the royal road to the unconscious,” a safety valve for unconscious desires, that reveal secrets of the unconscious part of the mind unknown to the conscious mind. Freud tried to analyze dreams to uncover the unconscious desires (many of them sexual) and fears disguised in dreams. He considered the remembered story line of a dream its manifest content, and the underlying meaning its latent content. Psychiatrists Robert McCarley and J. Alan Hobson proposed another theory of dreams called the activation-synthesis theory. During a dream, the pons generates bursts of action potentials to the forebrain, which is activation. The dreamer then tries to make sense of the stimulation by creating a story line, which is synthesis. The origin of dreams is psychological according to psychoanalysts, and physiological according to McCarley and Hobson. A cognitive view holds that when we sleep, information from the external world is largely cut off. So the only world our constantly active brain can model is the one already inside it from stored memories, recent concerns, current emotions, and expectations, which can be activated by electrical impulses discharged from within the brain. In other words, dreams are the interplay of the physiological triggering of brain waves and the psychological functioning of the imaginative, interpretive parts of the mind. Recent studies indicate correspondences between what you do in the dream state and what happens to your physical body and brain. Thus if you dream you’re doing something, to your brain, it’s as if you’re actually doing it.

Sleep Disorders

Chances are you’ve been sleep deprived at one time or another. When you get little or no sleep one night, you spend more of your sleep time the next night in REM sleep (called REM rebound), with few consequences. But millions of people suffer from chronic, long-term sleep disorders. The most common adult sleep disorders include insomnia, sleep apnea, and narcolepsy, while children are more likely to experience night terrors and sleepwalking. Insomniais the inability to fall asleep and/or stay asleep. Insomnia complainers typically overestimate how long it takes them to fall asleep and underestimate how long they stay asleep. Sleep researchers recommend that you go to bed at a set time each night and get up at the same time each morning; exercise for about a half hour daily 5 or 6 hours before going to bed; avoid alcohol, sleeping pills, and stimulants; avoid stress; and relax before bed to avoid insomnia. Narcolepsy is a condition in which an awake person suddenly and uncontrollably falls asleep, often directly into REM sleep. Victims often benefit from naps or drug therapy with stimulants or antidepressants. Sleep apnea is a sleep disorder characterized by temporary cessations of breathing that awaken the sufferer repeatedly during the night. Sleep apnea most often results from obstruction or collapse of air passages, which occurs more frequently in obese people. Weight loss and sleeping on the side can help alleviate the problem. An effective treatment is a positive pressure pump that provides a steady flow of air through a face mask worn by the sufferer. Night terrors are most frequently childhood sleep disruptions from stage 4 sleep characterized by a bloodcurdling scream and intense fear. Sleepwalking, also called somnambulism, is also most frequently a childhood sleep disruption that occurs during stage 4 sleep characterized by trips out of bed or carrying on of complex activities. Typically, sufferers do not recall anything in the morning.

Hypnosis

Hypnosis is an altered state of consciousness characterized by deep relaxation and heightened suggestibility. Under hypnosis, subjects can change aspects of reality and let those changes influence their behavior. Hypnotized individuals may feel as if their bodies are floating or sinking; see, feel, hear, smell, or taste things that are not there; lose sense of touch or pain; be made to feel like they are passing back in time; act as if they are out of their own control; and respond to suggestions by others. For some people, this make-believe may be so vivid and intense that they have trouble differentiating it from reality. Subjects can actually think immersing a hand in ice water is comfortable! Many psychologists think hypnosis involves highly focused awareness and intensified imagination. Other psychologists propose social cognitive theories that hypnosis is a social phenomenon in which highly motivated subjects enter a hypnotized “role.” Still others believe that hypnosis involves a division or dissociation of consciousness. According to the dissociation theory, hypnotized individuals experience two or more streams of consciousness cut off from each other. According to Ernest Hilgard, part of the consciousness responds to suggestions, while the other, the “hidden observer,” remains in the background monitoring behavior. Evidence for this dissociation of consciousness is provided by hypnotized subjects who indicate, for example, that a part of them is experiencing more pain with hands submerged in ice water than the hypnotized subjects acknowledge. After hypnosis, the individual may follow a posthypnotic suggestion and may have a thought or feeling without conscious knowledge of its hypnotically suggested source, or may experience posthypnotic amnesia, forgetting selected events by suggestion. One of the most important practical applications of hypnosis is in analgesia (pain control), which is used in surgery, childbirth, and dentistry.

Meditation

Do you know someone who practices yoga or meditates? Meditation is a set of techniques used to focus concentration away from thoughts and feelings in order to create calmness, tranquility, and inner peace. Meditation is popular in Asia, where Zen Buddhists meditate. EEGs of meditators show alpha waves characteristic of relaxed wakefulness. Physiological changes, such as lowered blood pressure, slowed heart rate and breathing rate, and warming of hands, common during meditation, indicate activation of the parasympathetic nervous system, which is normally not under conscious control. Meditators often report an increased feeling of well being. Psychologists disagree as to whether or not meditation is an altered state of consciousness.

Drugs

Do you drink coffee, tea, cocoa, or cola in the morning to get you going? Lots of people do. These beverages contain a psychoactive drug called caffeine. Psychoactive drugs are chemicals that can pass through the blood-brain barrier into the brain to alter perception, thinking, behavior, and mood, producing a wide range of effects from mild relaxation or increased alertness to vivid hallucinations. The effect a person expects from a drug partly determines the effect of the drug on that person. That person may experience different effects, depending on his/her mood and social situation. Psychoactive drugs stimulate or inhibit different regions of the brain by interacting with neurotransmitter systems. Psychological dependence develops when the person has an intense desire to achieve the drugged state in spite of adverse effects. If a person uses a drug repeatedly, the intensity of effects produced by the same dose may decrease, causing the person to take larger doses. This decreasing responsivity to a drug is called tolerance. Tolerance for drugs partly depends on environmental stimuli associated with taking of the drug. Physiological dependence or addiction develops when changes in brain chemistry from taking the drug necessitate taking the drug again to prevent withdrawal symptoms. Typically, withdrawal symptoms include intense craving for the drug and effects opposite to those the drug usually induces. Although hundreds of psychoactive drugs differ in their chemical composition, drugs can be classified into broad categories. One classification system categorizes drugs by their main effects: depressants, narcotics, stimulants, and hallucinogens.

Depressants are psychoactive drugs that reduce the activity of the central nervous system and induce relaxation. Depressants include sedatives, such as barbiturates, tranquilizers, and alcohol. Among the barbiturates are secobarbital (Seconal) and phenobarbital (Luminal). Sedatives are taken to induce sleep and prevent seizures. Tranquilizers include the benzodiazepines Valium, Xanax, and Rohypnol (“roofies”), as well as quaaludes. Rohypnol has been dubbed “The date rape drug.” Tranquilizers relieve anxiety, induce sleep, and prevent seizures. Because more people use alcohol than any other depressant, alcohol has been the most studied psychoactive chemical. It acts at many sites, including the reticular formation, spinal cord, cerebellum, and cerebral cortex, and on many neurotransmitter systems. Alcohol increases transmission of the neuroinhibitor GABA, decreases transmission of the excitatory neurotransmitter acetylcholine, and increases production of beta-endorphins. In low doses, alcohol produces a relaxing effect, reduces tension, lowers inhibitions, impairs concentration, slows reflexes, impairs reaction time, and reduces coordination. It lowers inhibitions by depressing activity in the frontal lobes, which usually control expression of emotions. In medium doses, alcohol produces slurred speech, drowsiness, and altered emotions. In high doses, alcohol produces vomiting, depressed breathing, unconsciousness, coma, and even death. Chronic drinking can lead to addiction. Withdrawal symptoms include shaking (tremors), sleep problems, nausea, hallucinations, and even seizures.

Narcotics are analgesics (pain reducers) which work by depressing the central nervous system. They can also depress the respiratory system. Narcotics include the opiates and synthetic opiates: codeine, heroin, morphine, opium, Percodan, Darvon, Talwin, Dilaudid, methadone, and Demerol. People take narcotics to induce feelings of euphoria, relieve pain, and induce sleep. Their chemical properties are very similar to the endorphins that our brains produce. Opiates are very physically and psychologically addictive.

Stimulants are psychoactive drugs that activate motivational centers and reduce activity in inhibitory centers of the central nervous system by increasing activity of serotonin, dopamine, and norepinephrine neurotransmitter systems. Stimulants include caffeine, nicotine, amphetamines, and cocaine. Stimulants are used to treat hyperactivity and narcolepsy. Among the amphetamines are methamphetamine, benzedrine, Ritalin, ephedrine (Ephedra), and ecstasy (MDMA), made popular at “all-night raves.” Amphetamines stimulate the sympathetic nervous system and speed up the metabolism, reducing appetite and making a person feel alert, energetic, and elated. Recent research indicates that MDMA damages brain cells. Cocaine and “crack cocaine” that is sniffed, smoked, swallowed, and injected are powerfully addicting drugs that produce feelings of euphoria, excitement, and strength and reduce hunger. Various doses of cocaine can also produce neurological and behavioral problems, such as dizziness, headache, movement problems, anxiety, insomnia, depression, hallucinations, high blood pressure, and stroke. Overdose results in death; comedian John Belushi died from a cocaine/heroin overdose.

Hallucinogens, also called psychedelics, are a diverse group of psychoactive drugs that alter moods, distort perceptions, and evoke sensory images in the absence of sensory input. Hallucinogens include lysergic acid diethylamide (LSD), phencyclidine (PCP), marijuana (THC), psilocybin from mushrooms, and mescaline (Peyote). Some users report profound, dreamlike feelings.

image Review Questions

Directions: For each question, choose the letter of the choice that best completes the statement or answers the question.

1. As you are reading this question, you are probably not thinking about what you ate for lunch. The memory of what you ate for lunch is most likely in your

(A) nonconscious

(B) preconscious

(C) unconsciousness

(D) sensory memory

(E) attention

2. Traveling in a jet plane from California to New York is most likely to

(A) disrupt your circadian rhythms

(B) prevent the onset of REM sleep

(C) stimulate your parasympathetic nervous system

(D) induce delta brain waves

(E) cause withdrawal symptoms

3. According to psychodynamic psychologists, the unconscious

(A) processes information of which you are unaware

(B) includes unacceptable feelings, wishes, and thoughts

(C) is characterized by loss of responsiveness to the environment

(D) is synonymous with the preconscious

(E) develops after the ego and superego

4. Of the following, which does your hypothalamus regulate over the course of 24 hours?

I. body temperature

II. hormonal levels

III. memory of the day’s events

(A) I only

(B) II only

(C) III only

(D) I and II only

(E) I, II, and III

5. “Humans developed a unique waking-sleep cycle that maximized our chances of survival,” is a statement most typical of

(A) developmental psychologists

(B) physiological psychologists

(C) psychoanalysts

(D) sociologists

(E) evolutionary psychologists

6. Which has enabled psychologists to learn the most about sleep processes over the last 50 years?

(A) psychopharmacology

(B) lesions

(C) EEGs

(D) CT scans

(E) MRI

7. Which stage of sleep is characterized by brain waves with spindles and K-complexes?

(A) stage 1

(B) stage 2

(C) stage 3

(D) stage 4

(E) REM

8. Nightmares most frequently occur during

(A) stage 1

(B) stage 2

(C) stage 3

(D) stage 4

(E) REM

9. During paradoxical sleep, muscles seem paralyzed and

(A) eyes dart about in various directions

(B) breathing is slow and shallow

(C) night terrors are likely

(D) sleepwalking occurs

(E) the sleeper is easily awakened

10. After her bridal shower, a young woman dreamed that she was dining with her parents when a young guy grabbed her wallet containing her driver’s license, credit cards, cash, and family pictures. She awoke in a cold sweat. After discussing the dream with a friend, she realized that she felt anxious about losing her identity in her approaching marriage. This explanation of her dream represents the

(A) manifest content

(B) latent content

(C) ego

(D) activation-synthesis theory

(E) cognitive analysis

11. Monitoring by the hidden observer during hypnosis provides evidence for

(A) the nonconscious

(B) activation-synthesis

(C) dissociation of consciousness

(D) role playing

(E) posthypnotic amnesia

12. Zen Buddhists and others practicing meditation are better able than most other people to stimulate their

(A) sympathetic nervous systems

(B) parasympathetic nervous systems

(C) somatic nervous systems

(D) salivation

(E) urination

13. Of the following, which pair of psychoactive drugs shares the most similar effects on the brain?

(A) alcohol–marijuana

(B) caffeine–morphine

(C) nicotine–heroin

(D) amphetamines–cocaine

(E) barbiturates–LSD

14. In small quantities, alcohol can be mistaken for a stimulant because it

(A) inhibits control of emotions

(B) stimulates the sympathetic nervous system

(C) speeds up respiration and heartbeat

(D) induces sleep

(E) affects the cerebellum

image Answers and Explanations

1. B—Memories that can easily be brought into consciousness are in the preconscious level of consciousness.

2. A—Crossing time zones can change the amount of light and dark your body gets and alter your sleeping/waking cycle, secretion of hormones, etc. This disrupts your circadian rhythms.

3. B—According to psychoanalysts/psychodynamic psychologists, the unconscious harbors unacceptable thoughts, wishes, and feelings that can be revealed in dreams, through hypnosis, etc.

4. D—The hypothalamus regulates body temperature, blood pressure, pulse, blood sugar levels, hormonal levels, etc.

5. E—Evolutionary psychologists believe that adaptive behavior persists because of natural selection. Those who have that trait survive, reproduce, and pass on their traits.

6. C—Of the choices, only electroencephalograms can reveal function. Before the use of EEGs, people thought that little brain activity went on during sleep.

7. B—EEGs of stage 2 sleep are characterized by waves showing sleep spindles and K-complexes.

8. E—Nightmares are unpleasant, complex dreams that occur mainly during REM sleep.

9. A—A paradox is something contradictory that is true. REM sleep is considered paradoxical sleep because the eyes are darting around, brain waves are similar to being awake, but the muscles of the arms and legs are inactive.

10. B—Freudians believe the hidden meaning of a dream is its latent content.

11. C—Ernest Hilgard demonstrated that when people are hypnotized, some part of their consciousness—the hidden observer—is passively aware of what is happening.

12. B—Ordinarily we lack the ability to activate our parasympathetic nervous systems to any significant extent, but we can easily activate the other functions listed.

13. D—Amphetamines and cocaine are both classified as stimulants.

14. A—After drinking small amounts of alcohol, people are often lively and seem uninhibited. This results from inhibition of part of the frontal lobes that usually keep emotions in check.

image Rapid Review

Consciousness—our awareness of the outside world and of ourselves, including our own mental processes, thoughts, feelings, and perceptions. EEGs show alpha and beta waves.

Levels of consciousness:

• Normally conscious, what you pay attention to is what you process into perceptions, thoughts, and experiences. Attention is a state of focused awareness.

Preconscious—level of consciousness that is outside of awareness but contains feelings and memories that can easily be brought to conscious awareness.

Unconscious (subconscious)—level of consciousness that includes often unacceptable feelings, wishes, and thoughts not directly available to conscious awareness.

Nonconscious—the level of consciousness devoted to processes completely inaccessible to conscious awareness.

Hypothalamus controls your biological clock, regulating changes in blood pressure, body temperature, pulse, blood sugar levels, hormonal levels, activity levels, sleep, and wakefulness over 24 hours in normal environment (25 hours in a place without normal night–day).

Circadian rhythms—daily patterns of changes.

Reticular formation (reticular activating system)—neural network in brainstem (medulla and pons) and midbrain essential to the regulation of sleep, wakefulness, arousal, and attention.

States of consciousness include: (normal waking) consciousness, daydreaming, sleep, hypnosis, meditation, and drug-induced states.

Sleep is a complex combination of states of consciousness, each with its own level of consciousness, awareness, responsiveness, and physiological arousal.

Stage 1 sleep—quick sleep stage with gradual loss of responsiveness to outside, drifting thoughts, and images (the hypnagogic state). EEGs show theta waves.

Stage 2 sleep—about 50% of sleep time. EEGs show high-frequency sleep spindles and K-complexes.

Stage 3 sleep—deep sleep stage. EEGs show some high-amplitude, low-frequency delta waves.

Stage 4 sleep—deepest sleep stage. EEGs show mostly delta waves. Slowed heart rate and respiration, lowered temperature and lowered blood flow to the brain. Growth hormone secreted.

REM sleep (Rapid Eye Movement sleep)—sleep stage when eyes dart about. About 80% dreaming, 5 to 6 times each night (about 20% of sleep time). Called paradoxical sleep because EEGs are similar to stage 1 and wakefulness, but we are in deep sleep with skeletal muscles paralyzed.

NREM (Non-REM sleep)—sleep stages 1 through 4 without rapid eye movements.

During sleep we synthesize proteins and consolidate memories from the preceding day.

Sleep disorders include insomnia, the inability to fall asleep and/or stay asleep; narcolepsy, sudden and uncontrollable lapse into sleep (usually REM); and sleep apnea, temporary cessations of breathing that awaken the sufferer repeatedly during the night. Sleep disruptions include night terrors, characterized by bloodcurdling screams and intense fear in children during stage 4 sleep; and sleepwalking (somnambulism), usually in children during stage 4 sleep.

Three theories of what dreams mean:

1. To [Freudian] psychoanalysts, dreams are a safety valve for unconscious desires. Manifest content—according to Freud, the remembered story line of a dream. Latent content—according to Freud, the underlying meaning of a dream.

2. Activation-synthesis theory—during REM sleep the brainstem stimulates the fore-brain with random neural activity, which we interpret as a dream.

3. Cognitive information processing theory—dreams are the interplay of brain waves and psychological functioning of interpretive parts of the mind.

Daydreaming—state with focus on inner, private realities, which can generate creative ideas.

Hypnosis—state with deep relaxation and heightened suggestibility. The hidden observer provides evidence for dissociation of consciousness.

Meditation—set of techniques used to focus concentration away from thoughts and feelings in order to create calmness, tranquility, and inner peace.

Psychoactive drug—a chemical that can pass through the blood-brain barrier to alter perception, thinking, behavior, and mood.

Four categories of psychoactive drugs:

1. Depressants—reduce activity of CNS and induce sleep.

2. Narcotics—depress the CNS, relieve pain, induce feelings of euphoria.

3. Stimulants—activate motivational centers; reduce activity in inhibitory centers of the CNS.

4. Hallucinogens—distort perceptions and evoke sensory images in the absence of sensory input.

Psychological dependence—person has intense desire to achieve the drugged state in spite of adverse effects.

Physiological dependence (addiction)—blood chemistry changes from taking a drug necessitate taking the drug again to prevent withdrawal symptoms.

Withdrawal symptoms—typically intense craving for drug and effects opposite to those the drug usually induces.