Many behaviors trigger predictable results. You strike the same piano key repeatedly and hear the same note each time. You flick a light switch today, and the bulb glows exactly as it did yesterday. This cause-and-effect consistency does not extend to the effects of psychoactive drugs. Individuals respond to drugs in remarkably different ways at different times.

Ellen is a healthy, attractive, intelligent 19-year-old university freshman who knows the risks of unprotected sexual intercourse. She learned about HIV and other sexually transmitted diseases (STDs) in her high school health class. A seminar about the dangers of unprotected sexual intercourse was part of her college orientation: seniors provided the freshmen in her residence free condoms and safe sex literature. Ellen and her former boyfriend were always careful to use latex condoms during intercourse.

At a homecoming party in her residence hall, Ellen has a great time, drinking and dancing with her friends and meeting new people. She is particularly taken with Brad, a sophomore at her college, and the two of them decide to go back to her room to order a pizza. One thing leads to another, and Ellen and Brad have sexual intercourse without using a condom. The next morning, Ellen wakes up, dismayed and surprised at her behavior and concerned that she may be pregnant or may have contracted an STD. She is terrified that she may have AIDS (MacDonald et al., 2000).

What happened to Ellen? What is it about drugs, especially alcohol, that make people sometimes do things they would not ordinarily do? Alcohol links to many harmful behaviors that are costly both to individuals and to society. These harmful behaviors include not only unprotected sexual activity but also driving while intoxicated, date rape, spousal or child abuse and other aggressive behaviors, and crime. Among the explanations for alcohol’s effects are disinhibition, learning, and behavioral myopia.

Disinhibition and Impulse Control

An early and still widely held explanation of alcohol’s effects is disinhibition theory. It holds that alcohol has a selective depressant effect on the cortical brain region that controls judgment while sparing subcortical structures, those responsible for more instinctual behaviors, such as desire. Stated differently, alcohol depresses learned inhibitions based on reasoning and judgment while releasing the “beast” within.

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A variation of disinhibition theory argues that the frontal lobes check impulsive behavior. According to this idea, impulse control is impaired after drinking alcohol because of a higher relative sensitivity of the frontal lobes to alcohol. A person may then engage in risky behavior (Hardee et al., 2014).

Proponents of these theories often excuse alcohol-related behavior, saying for example, “She was too drunk to know better” or “The boys had a few too many and got carried away.” Do disinhibition and impulse control explain Ellen’s behavior? Not entirely. Ellen had used alcohol in the past and managed to practice safe sex despite its effects. Neither theory explains why her behavior was different on this occasion. If alcohol is a disinhibitor, why is it not always so?

Learning

Craig MacAndrew and Robert Edgerton (1969) questioned disinhibition theory along just these lines in their book Drunken Comportment. They cite many instances in which behavior under the influence of alcohol changes from one context to another. People who engage in polite social activity at home when consuming alcohol may become unruly and aggressive when drinking in a bar.

Even behavior at the bar may be inconsistent. Take Joe, for example. While drinking one night at a bar, he acts obnoxious and gets into a fight. On another occasion, he is charming and witty, even preventing a fight between two friends; on a third occasion, he becomes depressed and worries about his problems. MacAndrew and Edgerton also cite examples of cultures in which people are disinhibited when sober only to become inhibited after consuming alcohol and cultures in which people are inhibited when sober and become more inhibited when drinking. What explains all these differences in alcohol’s effects?

MacAndrew and Edgerton suggested that behavior under the effects of alcohol is learned. Learned behavior is specific to culture, group, and setting and can in part explain Ellen’s decision to sleep with Brad. Where alcohol is used to facilitate social interactions, behavior while intoxicated is a time-out from more conservative rules regarding dating.

Behavioral Myopia

But Ellen’s lapse in judgment regarding safe sex is more difficult to explain by learning theory. Ellen had never practiced unsafe sex before and had never made it a part of her time-out social activities. So why did she engage in it with Brad?

A different explanation for alcohol-related lapses in judgment, behavioral myopia (nearsightedness), is the tendency for people under the influence of (in this case) alcohol to respond to a restricted set of immediate and prominent cues while ignoring more remote cues and possible consequences. Immediate and prominent cues are very strong and obvious and close at hand (Griffin et al., 2010).

In an altercation, the person with behavioral myopia will be quicker than usual to throw a punch, because the fight cue is so strong and immediate. At a raucous party, the myopic drinker will be more eager than usual to join in, because the immediate cue of boisterous fun dominates his or her view. Once Ellen and Brad arrived at Ellen’s room, the sexual cues at the moment were far more immediate than concerns about long-term safety. As a result, Ellen responded to those immediate cues and behaved atypically.

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Behavioral myopia can explain many lapses in judgment that lead to risky behavior—aggression, date rape, and reckless driving while intoxicated. Individuals who have been drinking may also have poor insight into their level of intoxication: they may assume that they are less impaired than they actually are (Sevincer and Oettingen, 2014).

B. G. started smoking when she was 13 years old. She has quit many times without success. After successfully abstaining from cigarettes by using a nicotine patch for more than 6 months, B. G. began smoking again. Because the university where she works has a no smoking policy, she has to leave campus and stand across the street to smoke. Her voice has developed a rasping sound, and she has an almost chronic “cold.” She says that she used to enjoy smoking but does not any more. Concern about quitting dominates her thoughts.

B. G. has a drug problem. She is one of the 25 percent or so of North Americans who smoke. Like B. G., most smokers realize that it is a health hazard, have experienced unpleasant side effects from it, and have attempted to quit but cannot. B. G. is exceptional only in her white-collar occupation. Today, most smokers are found in blue-collar occupations rather than among professional workers. And the use of electronic cigarettes (e-cigarettes) by young people is on the rise (Czoli et al., 2015). The health hazards posed by nicotine delivery via e-cigarettes are unknown.

Substance abuse is a pattern of drug use in which people rely on a drug chronically and excessively, allowing it to occupy a central place in their life. In a more advanced state of substance dependence, popularly known as addiction, people are physically dependent on a drug in addition to abusing it. They have developed tolerance for the drug and so require increased doses to obtain the desired effect.

Drug addicts may also experience unpleasant, sometimes dangerous physical withdrawal symptoms if they suddenly stop taking the abused drug. Symptoms can include muscle aches and cramps, anxiety attacks, sweating, nausea, and even, for some drugs, convulsions and death. Symptoms of alcohol or morphine withdrawal can begin within hours of the last dose and tend to intensify over several days before they subside.

Although B. G. abuses nicotine, she is not physically dependent on it. She smokes approximately the same number of cigarettes each day (she has not developed tolerance to nicotine), and she does not get sick if she is deprived of cigarettes (does not have severe withdrawal symptoms but does display irritability, anxiety, increased appetite, and insomnia). B. G. illustrates that the power of psychological dependence can be as influential as the power of physical dependence.

Many abused or addictive drugs—including sedative-hypnotics, antianxiety agents, opioids, and stimulants—have a common property: they produce psychomotor activation in some part of their dose range. That is, at certain levels of consumption, these drugs make the user feel energetic and in control. This common effect has led to the hypothesis that all abused drugs may act on the same target in the brain: dopamine in the mesolimbic pathways of the dopaminergic activating system. Drugs of abuse increase mesolimbic dopamine activity, either directly or indirectly, and drugs that blunt abuse and addiction decrease mesolimbic dopamine activity.

Vast differences in individual responses to drugs are due to differences in age, body size, metabolism, and sensitivity to a particular substance. Larger people, for instance, are generally less sensitive to a drug than smaller people are: their greater volume of body fluids dilutes drugs more. Old people may be twice as sensitive to drugs as young people are. The elderly often have less effective barriers to drug absorption as well as less effective processes for metabolizing and eliminating drugs from their body. Individuals also respond to drugs in different ways at different times.

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Females are about twice as sensitive to drugs as are males, on average, owing in part to their smaller size but also to hormonal differences. The long-held general assumption that human males are more likely to abuse drugs than are human females led investigators to neglect researching drug use and abuse in human females. But the results of recent research support quite the opposite view: females are less likely to become addicted to some drugs than are males, but females are catching up and for some drugs are surpassing males in the incidence of addiction.

Although the general pattern of drug use is similar in males and females, the sex differences are striking (Becker and Hu, 2008). Females are more likely than males to abuse nicotine, alcohol, cocaine, amphetamine, opioids, cannabinoids, caffeine, and PCP. Females begin to regularly self-administer licit and illicit drugs of abuse at lower doses than do males; females’ use escalates more rapidly to addiction; and females are at greater risk for relapse after abstinence.

Factors Influencing Individual Responses to Drugs

Before you continue, check your understanding.

Question 1

Question 2

Question 3

Question 4

Question 5

Answers appear in the Self Test section of the book.