Thus far in this chapter, we’ve discussed aspects of conscious experience that everyone normally experiences on a daily basis. Each day, you sometimes are awake and consciously experiencing the world; you sometimes are asleep and in mentally active REM sleep; and you sometimes are in the mentally quieter state of non-REM sleep.

In addition to these three mental states, people occasionally experience alterations in normal, everyday conscious experience. We’ll conclude the chapter by looking at three alterations in conscious states that are produced by meditation, hypnosis, and psychoactive drugs.

Try the following three-part exercise:

If you’re like most people, numerous thoughts flit in and out of your head. Even if you’re trying to concentrate on just one thing, or to clear your mind of everything, ideas invade your conscious experience. The contents of your own mind can seem out of your control (Wegner, 1994).

TRY THIS!

You likely experienced difficulty controlling the contents of your conscious mind when you attempted our Try This! activity. You were asked to try not to think of a white bear. But when asked to indicate when one came to mind, you probably indicated that the bear frequently popped back into consciousness—even though you were trying to keep it out. The contents of your conscious mind thus were not entirely under your control.

Can you gain greater control? People who meditate say you can. Meditation is any practice in which people focus their attention for an extended period of time (Walsh & Shapiro, 2006). Meditative methods are designed to increase people’s ability to concentrate. With practice, meditators gain greater ability to focus their minds on thoughts of their own choosing. The world’s cultures have produced numerous specific meditative techniques. Yet they can all be understood as one of two types (Goleman, 1988):

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The significance of meditation differs for different people. For many, it is a religious practice. A Hindu may meditate on the qualities of a deity to better understand the spiritual world; an Islamic Sufi meditator may seek closer spiritual connection to the Prophet Muhammad and to Allah; and Buddhists may meditate to understand, accept, and alleviate suffering (Goleman, 1988). For many clinical psychologists, meditation is a therapy method (Walsh & Shapiro, 2006). Irrespective of their religious beliefs, they judge that meditative practice can help clients become aware of their thoughts and feelings and gain greater control over their emotional life (Baer, 2003).

In this chapter, we won’t focus on either the religious or therapeutic purposes of meditation. Instead, we’ll examine a third implication of meditative practice. Meditation can inform psychological science about the full spectrum of human conscious experiences. It potentially reveals a “fourth state” of consciousness that “has nothing in common with the [other] three” (wakeful consciousness, REM sleep, and non-REM sleep; Arya, 1978, p. 5). In scientific terms, then, meditative practice uniquely reveals a phenomenon that requires scientific explanation—a distinct psychological state that Western scientists otherwise might overlook.

You may be skeptical of this claim. Meditators seem to be just sitting there, doing nothing. Have they really attained a unique conscious experience, with superior power to focus their attention and control the contents of their minds? To find out, let’s examine scientific evidence on the effects of meditation. We’ll consider evidence at two levels of analysis: the influence of meditation on (1) psychological processes of the mind, and (2) biological mechanisms in the brain.

MEDITATION AND PSYCHOLOGICAL PROCESSES. Eastern spiritual traditions have claimed, for millennia, that meditative practice enhances mental skills. It is only in recent years that scientific evidence has validated this claim (Tang & Posner, 2009).

In studying meditation, contemporary psychological scientists take two steps that were not previously taken by traditional practitioners of meditation. One involves measurement. Psychologists have devised tests to measure precisely the degree to which meditation improves people’s ability to focus their attention. The other is the experimental comparison of groups. Researchers systematically compare individuals who have and have not meditated.

In one study, researchers used an “attentional blink” task to measure people’s skill in concentrating attention (Slagter et al., 2007). Participants viewed a series of about 20 letters and numbers that appeared extremely rapidly (about 1/20 of a second) on a computer screen. On some trials, most of the stimuli were numbers, but some were letters. After these stimuli went zipping by, participants were asked to report the letters that appeared. This proved a difficult task. People’s minds tended to wander after they saw the first letter—their attention “blinked”—and they then missed the next letter presented. When two groups of participants attempted this task—(1) meditators trained for three months in meditation that focuses attention, and (2) non-meditators—meditators showed superior attentional ability. They were better able to sustain their attention to the rapidly presented stimuli, as indicated by their superior scores on the attentional blink task (Slagter et al., 2007). Scientific methods therefore confirmed ancient wisdom. Meditation improves people’s ability to focus their attention.

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MEDITATION AND BRAIN PROCESSES. Once you learn that meditation changes psychological abilities (specifically, the ability to focus attention), a new question arises: What brain mechanisms underlie these psychological changes? The psychological findings establish facts about the mind that can be explored at a biological level of analysis.

A clue to identifying the brain systems that meditation influences can be found in basic research on attention. Attention, the psychological process in which people focus their minds on an object or idea, has long been of interest to experimental psychologists (Kahneman, 1973; Triesman, 1964; see Chapter 5). Contemporary research explores attention at both psychological and biological levels of analysis and identifies parts of the brain that are particularly central to the focusing of attention (Posner & Rothbart, 2007). Here, then, is the clue: These brain systems may be the ones that change when people engage in meditative training (Lutz et al., 2008).

To find out, researchers conducted a brain-imaging study (Brefczynski-Lewis et al., 2007). Three groups of people participated: (1) novice meditators, with limited training in meditative techniques; (2) expert meditators with an average of 19,000 hours of meditation; and (3) highly practiced expert meditators, with an average of 44,000 hours of practice. (The latter two groups included people residing at meditative retreats, who meditate an average of 10 hours a day.) Participants in each group had their brains scanned during a meditation exercise in which they concentrated their attention on a small dot appearing on a video screen.

As predicted, the brain activity of expert meditators differed from that of non-meditators. When regions of the brain known to support attention were examined, the brains of meditators with 19,000 hours of practice were more active than those of novice meditators; meditative training thus influenced brain processes. Interestingly, when the brains of meditators with 44,000 hours of practice were examined, they were less active. For this highly expert group, the concentration task was so easy that it required little mental effort (Brefczynski-Lewis et al., 2007). Other researchers similarly have found large differences in brain activation when comparing novice meditators with Buddhist monks who were expert in meditative practice (Manna et al., 2010).

Research on meditation and the brain reinforces a conclusion about how the brain works. Brain systems are “plastic” (see Chapter 3). Neural connections are not entirely determined by your genetic makeup. Instead, the brain’s inner wiring changes as a result of your experience. Meditation is an experience that can significantly change the biology of the brain, and thus the mental abilities of the person.

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Most people learn something about hypnosis well before taking a psychology class. Popular culture—TV, movies—introduces us to the topic.

Here in a course on psychological science, you have to “unlearn” much of what popular culture has taught you. In the popular-culture story, hypnosis is a mysterious method of mind control. Stare at a watch for a few moments, and a hypnotist purportedly will have you in a trance, and soon you’ll be barking like a dog, clucking like a chicken, or heading to Elmer’s house to be turned into rabbit stew.

Research shows, however, that hypnosis does not really work this way. It is not a method of mind control (Raz & Shapiro, 2002). People who are hypnotized do not entirely lose conscious control of their thoughts and actions, although it is true that they may sometimes perform behaviors that, they report, occurred outside of their control. It also is not as mysterious as it may first appear. Recent advances suggest that hypnosis can be understood through normal methods of psychological science (Posner & Rothbart, 2011).

Hypnosis is an altered state of consciousness brought about through interaction between someone who makes suggestions to an individual (the “hypnotist”) and a hypnotic subject. When hypnotized, the hypnotic subject becomes highly suggestible, that is, his or her behavior is unusually responsive to suggestions from the hypnotist, rather than being driven by personal goals and intentions. Hypnosis, then, is not a method of mind control, yet it also is not mere myth. It is a genuine phenomenon with real psychological effects; as one expert summarized, “Hypnotized subjects can be oblivious to pain; they hear voices that aren’t there and fail to see objects that are clearly in their field of vision; they are unable to remember the things that happened to them while they were hypnotized; and they carry out suggestions after hypnosis has been terminated” (Kihlstrom, 2007, p. 445). Let’s look more closely at the questions of how hypnosis works and who can be hypnotized.

THE “HOW” AND “WHO” OF HYPNOSIS. Psychologists induce states of hypnosis through hypnotic induction procedures. A standard procedure, long in use, combines relaxation and focused attention (Weitzenhoffer & Hilgard, 1962). At the outset, the hypnotist informs participants that the process of hypnosis is up to them; they can achieve a hypnotic state only if they want to. (Note how this actual practice differs from the popular-culture myth that hypnotists can control the minds of unwitting victims.) Participants are encouraged to focus their attention on a specific target, such as a spot on a wall, while relaxing. The relaxation is very thorough; the hypnotist guides the process by suggesting that the participant’s muscles are relaxing, body is feeling heavy and tired, and eyelids are feeling heavy and needing to close. Once the hypnotic subject’s eyes close, the hypnotist instructs the subject to focus on the words of the hypnotist, and leads the person into a hypnotic state from which, the hypnotist suggests, the participant will not emerge until instructed to do so. Having reached this state, hypnotized people are highly suggestible. Their experiences are guided by the instructions of the hypnotist.

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You might be thinking, “This would never work on me.” If so, you may be right. Not everyone is hypnotizable. People differ considerably in their susceptibility to hypnosis.

Psychologists have developed procedures to identify who is, and is not, hypnotizable. In the Stanford Hypnotic Susceptibility Scale (Weitzenhoffer & Hilgard, 1962), the hypnotic subject undergoes an induction of the sort we just described and then receives suggestions regarding a series of tasks. Some are simple, such as the suggestion that one’s eyelids are getting heavy and are closing. Others are more elaborate. For example, the psychologist places three boxes in front of the subject and suggests, “I have placed two boxes in front of you … just two boxes. Do you see them?” (Weitzenhoffer & Hilgard, 1962, p. 44). Then the participants are asked what they see. The overall degree to which the subject responds to the suggestions indicates the depth to which the person has become hypnotized (e.g., saying “I see two boxes” would indicate greater depth). Results suggest that people differ widely in their hypnotizability. Only about one in eight or nine show substantial hypnotic effects on the full range of tasks (Kihlstrom, 2007).

In summary, then, hypnotic procedures can powerfully affect people’s psychological responses. But the strongest effects are seen in only a subset of highly hypnotizable people.

PSYCHOLOGICAL EVIDENCE OF HYPNOTIC EFFECTS. Why do hypnotic induction procedures affect people’s responses? There are two possibilities:

Many situations create social roles. At the doctor, you are expected to act in a manner consistent with the social role of “patient.” In class, you are expected to act according to the role of “student.” Possibility #2 suggests that, similarly, being in a hypnotic procedure causes people to act according to the role of “hypnotized person.” They adopt the role, convince themselves that they are hypnotized, and interpret their own behavior accordingly.

Which possibility do you think is correct? Before you try to answer that question, consider some research by the eminent psychologist Ernest Hilgard and his colleagues (Hilgard, Morgan, & Macdonald, 1975). They hypnotized participants and then asked them to put one of their hands in painfully cold water. Prior to this chilly experience, the hypnotist made two suggestions to participants: (1) They would not consciously experience any pain when their hand was in the water, but (2) a “hidden part” of them would be aware of the pain. The researchers then measured pain in two ways: (1) Participants reported consciously, in words, on their experiences; and, (2) in a procedure designed to tap the “hidden part” of the individual, participants typed numbers onto a keypad to indicate their level of pain.

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Hilgard and colleagues found that the conscious and “hidden” parts of hypnotized participants provided different pain reports (Hilgard et al., 1975). Consciously, hypnotized subjects reported little pain, despite having plunged a hand in frigid water. However, when typing numbers into a keypad, many participants reported that they were in pain.

The researchers interpreted this finding as evidence that hypnotized participants’ minds contain two parts that, through hypnosis, become disconnected. The conscious part truly experiences no pain, as a result of hypnosis. The “hidden part,” however, is aware of the pain.

Other research similarly shows the action of different parts of the mind. Hypnotized people have been shown information (e.g., a list of words) and then given a hypnotic suggestion for amnesia, that is, the suggestion that they will lose their memory of the material. Later, they are given tests of both explicit and implicit memory (Chapter 6). After the hypnotic suggestion, people lack explicit memory; they don’t consciously remember the material. Yet they do have implicit memory; when performing a task that requires them to think of a word, they tend to think of one that was on the previous word list (Kihlstrom, 2007). The results thus suggest that the mind contains at least two different memory systems.

This conclusion—strange as it may sound at first—is consistent with other findings in psychology. The behavior of split-brain patients (Chapter 3) reveals that their minds contain two parts. One can consciously discuss the person’s experiences, whereas the other can respond to stimuli but is unable to report on them consciously. Measures of “explicit” and “implicit” attitudes in social psychology often are poorly correlated with each other (Chapter 12), which suggests that people can be “of two minds” about a given topic.

What about the social role hypothesis? Some psychologists think that the findings of Hilgard and colleagues can be explained in terms of social roles (Spanos & Hewitt, 1980). Others, however, doubt this. They think it unlikely that the social role hypothesis can explain complex phenomena such as a participant’s different levels of performance on tests of implicit and explicit memory. In general, then, research suggests that—at least for highly hypnotizable people—the psychological effects of hypnosis are real.

BIOLOGICAL EVIDENCE OF HYPNOTIC EFFECTS. You still might be skeptical about hypnosis. It’s not impossible that the psychological evidence we just reviewed can be explained in terms of social roles. Biological evidence would be even more convincing. Since people generally cannot voluntarily control the activation of regions of their brains, any effects of hypnosis on brain functioning could not be explained by saying that people voluntarily adopted the social role of “hypnotized person.”

Researchers have, in fact, obtained such evidence. Using a research procedure similar to that of Hilgard and colleagues, researchers examined the effects of hypnosis on the experience of pain (Vanhaudenhuyse et al., 2009). They added a procedure unavailable to Hilgard decades earlier: fMRI, which enabled them to study brain activity during a painful task.

Highly hypnotizable participants took part in research procedures on two different days, during which they either were or were not hypnotized. The painful stimuli on both days were brief pulses of a laser directed to the back of the left hand. (The laser stimulated pain receptors, thereby producing a sensation of pain.) Researchers recorded brain activity and also asked participants to rate the severity of the pain they experienced.

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As in prior research, hypnosis reduced conscious pain. Participants reported less pain on the day they were hypnotized. In addition, hypnosis influenced brain activation. When participants were not hypnotized, the laser pulses caused activation in a wide variety of brain regions. However, when they were hypnotized, these same stimuli remarkably “failed to elicit any cerebral activation” (Vanhaudenhuyse et al., 2009, p. 1050; Figure 9.7). Hypnosis apparently caused high-level brain regions to influence lower-level regions of the brain that are directly involved in the experience of pain.

The key finding, then, is that identical stimuli had different effects on neural activity when participants were hypnotized. This should be enough to convince even the skeptic that hypnosis is a real phenomenon that influences both mind and brain.

A while back, some residents of the Caribbean wanted to alter their conscious states. They did so the quick way: They took out their paraphernalia—bowls for burning and tubes for inhaling—and used drugs. Is their drug use a sign of the moral decay of modern society? Well, no; it was quite a while back. The drug paraphernalia, researchers determined, was about 2400 years old (Fitzpatrick et al., 2009). Study of prehistoric societies reveals signs of similar drug use in multiple regions of the world, including the Americas and Europe (Echeverría & Niemeyer, 2013; Rudgley, 1995).

Humans, then, have long used psychoactive drugs. A psychoactive drug is any chemical substance that affects the nervous system in a manner that alters conscious experience. Psychoactive drugs exert these effects by changing communications among cells in the nervous system.

Once people begin abusing drugs, it can be difficult for them to stop—even when they can see that it is harming their own health (Everitt et al., 2008). Such users suffer from drug addiction, a compulsive, habitual, uncontrollable use of a harmful chemical substance (National Institute on Drug Abuse [NIDA], 2010). Drug addiction is widespread. Researchers estimate that 25 million people worldwide are addicted to psychoactive drugs (United Nations Office on Drugs and Crime [UNODC], 2009).

Why are psychoactive drugs so addicting? It’s primarily because they activate a reward center in the brain (Tan, Rudolph, & Lüscher, 2011). The brain’s reward center normally produces pleasurable feelings when organisms engage in activities that are naturally rewarding, such as eating or sex. Drugs artificially activate this reward system and thereby directly create such feelings of pleasure. This makes them highly addicting. (Chapter 11 discusses motivational processes and brain mechanisms that can cause people to become addicted to stimulant drugs.)

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There are different types of psychoactive drugs. We’ll examine four: hallucinogens, opioids, stimulants, and depressants.

HALLUCINOGENS. Hallucinogens are substances that profoundly alter consciousness, causing people to experience phenomena such as hallucinations and a loss of contact with reality. Hallucinogenic effects have long been experienced across the globe. Traditional cultures in Central America, South America, and South Asia have used hallucinogens in religious ceremonies for centuries (Nichols, 2004).

Traditional cultures discovered the effects of hallucinogenic substances that occur naturally. “Magic” mushrooms found in Mexico and South America, for example, produce hallucinogenic effects because they contain psilocybin, a chemical substance that powerfully alters mental experiences.

More recently, people have produced hallucinogens synthetically, that is, by combining chemicals in a laboratory. The first to do so was Albert Hoffman, a Swiss chemist working on drugs for migraine headaches. In 1943 he reported an unusual experience: “a not unpleasant intoxicated-like condition, characterized by an extremely stimulated imagination. In a dreamlike state … I perceived an uninterrupted stream of fantastic pictures, extraordinary shapes with intense, kaleidoscopic play of colors” (Hoffman, 1979, p. 47). Hoffman had been working on LSD (lysergic acid diethylamide) and guessed that a small amount of LSD must have been absorbed into his skin, causing the psychological effects. To test his idea, Hoffman next ingested 0.25 milligrams of the drug. It was more than enough:

Everything in my field of vision wavered and was distorted as if seen in a curved mirror…. Everything in the room spun around, and the familiar objects and pieces of furniture assumed grotesque, threatening forms…. I was seized by the dreadful fear of going insane.

—Hoffman (1979, pp. 48–49)

Hoffman had experienced the first LSD “trip.”

For two decades after Hoffman’s discovery, few people in the United States experienced LSD trips. But the drug gained popularity in the 1960s, due largely to the efforts of two psychologists at Harvard University, Timothy Leary and Richard Alpert (Lattin, 2010). They first experienced hallucinogens when sampling magic mushrooms in Mexico. They then experimented with LSD and became convinced that it was beneficial, awakening users to new, enlightening conscious experiences. Leary and Alpert gave the drug to colleagues, writers, artists, and even their students. They launched a campaign to get people, as Leary put it, to “turn on, tune in, and drop out” of mainstream society by exploring LSD’s mind-expanding powers.

Their campaign was remarkably successful. Hallucinogens became a staple of the 1960s counterculture. Popular music and art reflected, and contributed to, growth in the use of these drugs.

Today, hallucinogen use persists. About 1% of teens and 7% of young adults in the United States have tried LSD at least once (Substance Abuse and Mental Health Services Administration [SAMHSA], 2010). It persists despite legal sanctions: Possession of hallucinogens is illegal. It persists despite health risks: Hallucinogens can impair health through multiple routes. For example, some users feel that they have superhuman powers and attempt bizarre, dangerous activities such as trying to fly (Nichols, 2004). Another risk is psychological. Among people who are predisposed to psychological distress, the disturbing alterations of consciousness that hallucinogens create can trigger depression or psychosis, that is, a loss of the normal ability to understand the world of reality (Nichols, 2004).

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Some readers of this text may be seeking an expansion of conscious experience. If so, compare pills to skills. As you learned above, the skills of meditation enhance conscious awareness—without the costs, legal jeopardy, and health risks of hallucinogens.

What biological processes explain LSD’s psychological effects? The drug affects the actions of the neurotransmitter serotonin (Aghajanian & Marek, 1999; Nichols, 2004). When people take LSD, brain cells that are activated by serotonin—“serotonergic” neurons—fire abnormally. Serotonergic neurons are found in multiple regions of the brain. As a result, LSD has widespread biological, and thus psychological, effects.

Evidence indicates that hallucinogens may have additional biological effects (Fantegrossi, Murnane, & Reissig, 2008). Both LSD and the psilocybin found in magic mushrooms uniquely influence the inner workings of brain cells in the cortex (González-Maeso et al., 2007). The resulting combination of effects—on (1) a neurotransmitter (serotonin) used for communication between cells and on (2) biological activity within individual cells—may explain why hallucinogenic effects are so powerful.

OPIOIDS. Opioids are chemical substances whose primary psychoactive effect is the reduction of pain. They reduce pain by attaching themselves to nervous system cells that are involved in generating pain and related emotions (Holden, Jeong, & Forrest, 2005). Through such action, the drug morphine, for example, lessens the transmission of pain signals from the body to the brain, thereby lowering the conscious experience of pain.

Pain reduction is not the opioids’ only psychoactive effect. Opioids can also produce powerful feelings of euphoria and ecstasy (van Ree, Gerrits, & Vanderschuren, 1999). This makes opioid drugs highly addictive. People crave the positive feelings they create and seek to avoid the withdrawal symptoms—agitation, insomnia, muscular aches—that occur when drug use is stopped. Opioid addiction is a significant health risk. For instance, opioids can cause fatal respiratory system failures, especially if used in combination with other drugs (NIDA, 2011).

You don’t need to take drugs to experience the pain-relieving effects of opioids. You’ve got them in your system already. The body naturally produces endogenous opioids (endogenous means “originating within the body”). Just like opiate drugs that people ingest, the body’s endogenous opioids lessen pain by reducing the transmission of pain signals from the spinal cord to the brain (Holden et al., 2005). Research shows that intense exercise increases levels, within the brain, of endogenous opioids—especially endorphins, one of the opioids produced endogenously (Landolfi, 2012; Scheef et al., 2012). As a result, athletes may perform at high levels despite seemingly painful injuries. The endogenous opioid system blunts their conscious experience of pain.

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STIMULANTS. Stimulants are psychoactive drugs that increase nervous system activity and thus enhance alertness and energy. Stimulants also can enhance people’s sense of psychological well-being and self-esteem, as well as lower their inhibitions (Gawin & Ellinwood, 1988).

You might be in easy reach of the most commonly ingested stimulant drug right now: caffeine, a chemical compound found in coffee, tea, energy drinks, sodas, and chocolate. Caffeine increases alertness by interfering with naturally occurring biochemical processes that decrease brain activity (e.g., when you’re sleepy; Ribeiro & Sebastião, 2010). Although caffeine’s psychoactive effects are milder than those of some other stimulants, it still can be addicting. If regular users suddenly quit taking caffeine, they experience withdrawal symptoms such as headache and fatigue that are caused by changes in cerebral blood flow (Sigmon et al., 2009).

Another stimulant, nicotine, is found in tobacco products. Nicotine triggers the release of neurotransmitters that increase alertness, as well as a neurotransmitter, dopamine, that enhances feelings of pleasure and emotional well-being (see Chapter 7). Alertness and well-being might sound good. But getting them through the nicotine in tobacco products isn’t worth the costs. Tobacco use is extraordinarily harmful to health. Smoking is estimated to have killed 100 million people in the twentieth century, and it is projected to kill many times that number in the twenty-first (NIDA, 2010), due to persistently high smoking rates worldwide (Giovino, 2012).

Ritalin is a stimulant drug that is sometimes prescribed to treat attention-deficit hyperactivity disorder (ADHD), a condition marked by high distractibility, low ability to concentrate, and impulsive behavior such as fast and frequent moving and talking (NIH, 2012). Ritalin lessens ADHD symptoms by affecting neural communication in the brain’s frontal cortex, a region needed for sustained concentration and the control of behavior (Devilbiss & Berridge, 2008).

Amphetamines are powerful stimulants that increase alertness and produce euphoric feelings by affecting multiple neurotransmitters, including dopamine (Berman et al., 2009). Amphetamines have practical medical uses. However, both amphetamines and methamphetamines (a chemically similar stimulant) are used illegally as recreational drugs. More than half a million Americans at any given time use these drugs for the rush of energy and positive emotions they produce (SAMHSA, 2009). Cocaine, another simulant, has similar effects on conscious experience and thus is also highly addictive. Cocaine’s effects are particularly powerful when the drug is processed into a form that can be smoked, known as crack cocaine (Schifano & Corkery, 2008).

A drug that has gained in popularity in recent years is ecstasy, which is both a stimulant and a hallucinogen. Ecstasy can reduce anxiety and create feelings of intimacy and euphoria—effects that have added to its popularity. However, ecstasy also harms physical health; for example, it can abnormally raise body temperature and thus induce heat stroke (Rogers et al., 2009).

DEPRESSANTS. Depressants are psychoactive drugs that reduce arousal in the central nervous system. In so doing, they can lower conscious experiences of excitability and anxiety. Depressants achieve these effects in part by increasing the effects of inhibitory neurotransmitters, that is, neurotransmitters that reduce activity in the brain (Julien, 2005).

One class of widely used depressants is benzodiazepines, psychoactive drugs that reduce feelings of anxiety while also inducing muscular relaxation and sleepiness (Tan et al., 2011). Because of these effects, benzodiazepines such as Valium, Xanax, and Ativan are prescribed frequently to treat anxiety disorders (see Chapter 15). In addition to reducing anxiety, benzodiazepines activate the brain’s reward center and thus produce pleasurable feelings. This makes them particularly addicting.

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The most commonly used depressant of all is alcohol, a chemical compound found in beer, wine, and spirits. Beverages containing alcohol, which enhances the action of inhibitory neurotransmitters in the brain and reduces the action of excitatory neurotransmitters (Valenzuela, 1997), have been part of human societies for millennia. Various 7000-year-old jars for holding wine have been found in Iran, and 9000-year-old containers for a beerlike brew have been found in China (Gately, 2008). Humans thus have long experienced the feelings of relaxation and the lessening of inhibitions that alcohol can produce. Of course, this means people have also experienced its negative effects. Drinking impairs decision making and performance. High levels of chronic alcohol use can damage areas of the brain needed for memory and the control of motor movements (NIDA, 2010).

How does alcohol affect behavior? It depends. Sometimes, a few drinks can make people warm and outgoing. At other times, drinking may cause those same individuals to become hostile and belligerent. Understanding these differences requires multiple levels of analysis: not just a brain level of analysis (the effects of alcohol on neural communication) but a mind level (analysis of the specific thinking processes that alcohol affects) and person level (in particular, consideration of the social setting in which the person is drinking).

At the level of the mind, alcohol has two notable effects: (1) reducing the amount of information in a situation that people can pay attention to and (2) impairing individuals’ ability to think deeply about that information (Steele & Josephs, 1990). In short, drinking impairs thinking. This impact of alcohol on mental processes, in turn, helps to explain the impact of drinking on people’s social behavior.

People who have been drinking are strongly affected by social cues. They are particularly influenced (before their attention is heavily impaired) by cues that happen to grab their attention. If they notice others who are pleasant, alcohol may increase their warmth and pleasantness. If they notice someone who they think is insulting them, alcohol may increase their belligerence. This is why the effects of alcohol on behavior “depend.” They depend on cues in a person’s immediate social environment.

Finally, let’s conclude our discussion of psychoactive substances with the most frequently used illicit drug, marijuana (NIDA, 2014). Marijuana is a difficult drug to classify, for two reasons. First, it produces a wide range of effects; marijuana can influence both conscious feelings and thinking abilities. Second, its effects vary; the exact influence of the drug on any given occasion depends on the amount of marijuana consumed, as well as on individual differences in people’s reaction to the drug (Ameri, 1999).

Despite these variations, there is a pattern of effects that occurs commonly. Users tend to experience feelings of euphoria accompanied by a relaxed, tranquil state (Ameri, 1999). These effects are caused by a chemical substance in marijuana, tetrahy-drocannabinol (THC), that affects the activity of cells in the brain. Specifically, THC affects neural activity in parts of the brain that contribute not only to emotional states (e.g., pleasurable feelings), but also to cognition (memory, thinking, concentration). The widespread biological influence explains its wide range of psychological effects.

In the past, public health officials sometimes exaggerated the negative effects of marijuana use. Today, by contrast, users may enjoy the drug’s psychological effects while giving little thought to its potential long-term costs. Yet costs exist. Consider research that compared (1) people who never used marijuana to (2) people who used marijuana consistently across a long span of life, from their late teenage years to their 30s (Meier et al., 2012). This study’s key dependent variable was intelligence test scores; researchers examined participants’ IQ scores (see Chapter 8) early and later in life. They found that, over time, persistent marijuana users became less intelligent. Persistent users lost about 6 IQ points, whereas the IQ scores of nonusers went up slightly across the course of the study.

Table 9.1 summarizes the psychoactive drugs we have reviewed, plus selected additional drugs whose use is relatively widespread.

*The short-term effects of psychoactive drugs can vary from one person to another. In addition to short-term effects, many psychoactive drugs have major negative effects on psychological and physical health. The United States’ National Institute on Drug Abuse estimates that alcohol abuse and illegal drug use contribute to more than 100,000 deaths annually and that tobacco use is linked to more than 4 times that number of annual deaths (NIDA, 2010).

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