Personality disorders involve impairments in personality that cause great distress to an individual or impair his or her ability to get along with others, and the presence of pathological traits such as excessive hostility or callousness.

Borderline personality disorder characterizes people who have the personality trait of extremely negative emotionality and who are unable to regulate their emotions. They have a history of intense but unstable relationships in which they alternate between idealizing the partner and then devaluing the partner. They frantically try to avoid real or imagined abandonment by others, even if the “abandonment” is only a friend's brief vacation. They are self-destructive and impulsive, suffer chronic feelings of emptiness, and often threaten to commit suicide (which about 10 percent of them do). They are emotionally volatile, careening from anger to euphoria to anxiety (Crowell, Beauchaine, & Linehan, 2009; Schulze, Schmahl, & Niedtfeld, 2015). They love and hate intensely, sometimes simultaneously. (The term borderline comes from the original psychodynamic view of the disorder, as one thought to fall on the border between mild and severe mental illnesses, thereby creating an inconsistent ability to function in the world.)

Many people with borderline disorder deliberately injure themselves in repeated acts of cutting and self-mutilation. This form of “nonsuicidal self-injury” has been known for thousands of years and is found around the world; it is most prevalent among adolescents and young adults. Self-injury has two functions: It reduces stress and arousal within the individual, and it often produces social support or relieves the person of unwanted social obligations (Nock, 2010).

Although there has not been much empirical research on the development of borderline personality disorder, a leading theory is based on a “biosocial” model proposed by Marsha Linehan, who suffers from the disorder herself (and has developed one of the most successful treatments for it). In this view, a child is born with a genetic vulnerability that produces abnormalities in the frontal lobes and brain areas involved in emotion, and a disposition toward negative emotionality as a personality trait. As a result, the young child behaves impulsively and has heightened emotional sensitivity, which in turn are worsened by what Linehan calls an “invalidating environment”: The child's parents do not acknowledge or tolerate the child's emotions and their expression, telling the child that those feelings are unjustified and the child should cope with them alone. At the same time, the parents intermittently reinforce the child's extreme emotional outbursts with their attention. As a result of getting these mixed messages, the child doesn't learn to understand and label what he or she is feeling, or how to regulate those feelings calmly. Instead, the child veers helplessly between trying to inhibit any sign of emotion and giving in to extreme expressions of it (Crowell, Beauchaine, & Linehan, 2009).

For several editions, the DSM has defined antisocial personality disorder (APD) in terms of behavior, describing people who repeatedly break the law and violate the rights of others; are impulsive and seek quick thrills; show reckless disregard for their own safety or that of others; often get into physical fights or assault others; and are irresponsible, failing to hold jobs or meet obligations. The problem with this definition is that it covers a grab-bag set of behaviors without specifying what the underlying mental disorder might be. Moreover, it could apply both to people who fall in with a bad crowd for a few years and to others who, as one researcher describes them, are “lifetime persistent offenders.” For the latter, rule-breaking and irresponsibility start in early childhood and take different forms at different ages: “biting and hitting at age 4, shoplifting and truancy at age 10, selling drugs and stealing cars at age 16, robbery and rape at age 22, and fraud and child abuse at age 30” (Moffitt, 1993, 2005). Individual differences in aggressiveness are eerily apparent by an infant's first birthday, virtually as soon as a baby has the motor skills to hit or exert force, and seem to be an early predictor of later violence (Baker et al., 2013; Hay et al., 2011).

Many people with APD don't do as well as other individuals on neuropsychological tests of frontal lobe functioning, and they have less gray matter in the frontal lobes than other people do (Dinn & Harris, 2000; Raine, 2008). The frontal lobes are responsible for planning and impulse control, and impairments in this area can lead to an inability to control responses to frustration and provocation, to regulate emotions, and to understand the long-term consequences of indulging in immediate gratifications (Fairchild et al., 2013). One PET-scan study found that cold-blooded, predatory murderers had less brain activity in the frontal lobe than did men who murdered in the heat of passion or a control group of criminals who had not murdered anybody (Raine et al., 1998). Frontal lobe damage can be inherited or result from disease, accident, or physical abuse (Milner & McCanne, 1991), or perhaps from a genetic predisposition: In a longitudinal study of boys who had been physically abused in childhood, those who had a variation in a crucial gene later had far more arrests for violent crimes than did abused boys who had a normal gene (Caspi et al., 2002). Although only 12 percent of the abused boys had this variant, they accounted for nearly half of all later convictions for violent crimes.

As we keep reminding you, however, genes are not destiny. In the study we just described, boys who had the genetic variant but whose parents treated them lovingly did not grow up to be violent. Genes may affect the brain, in turn predisposing a child to rule-breaking and violent behavior, but many environmental influences can disrupt that pathway and alter the ways that genes express themselves. One is poor nutrition in the first 3 years of life, which has been linked with antisocial behavior up through adolescence; so has early separation from the mother; and so has brain damage caused by parental cruelty (Raine, 2008).

Over the objections of many clinical scientists, the DSM does not use the term psychopathy, which the DSM regards as one form of APD. The DSM-5, however, added another criterion for the diagnosis: lacking remorse for harms inflicted on others. This is the key symptom of psychopathy, which we describe next.

Decades ago, Hervey Cleckley (1976) popularized the term psychopathy [“sigh CAW pa thee”], which he used to describe individuals who are heartless, utterly lack conscience, and are unable to feel normal emotions. Psychopaths are incapable not only of remorse but also of fear of punishment and of shame, guilt, and empathy for those they hurt. If caught in a lie or a crime, psychopaths may seem sincerely sorry and promise to make amends, but it is all an act. Some psychopaths are violent and sadistic, able to kill a pet, a child, or a random adult without a twinge of regret, but others are charming and manipulative, able to direct their energies into con games or career advancement, abusing other people emotionally or economically rather than physically (Skeem et al., 2011). One researcher in this field, Robert Hare, calls corporate psychopaths “snakes in suits” (Babiak & Hare, 2007).

Although psychopaths are probably more prevalent in individualistic Western societies, they are believed to exist in all cultures and throughout history. Even a close-knit culture such as the Yupik in Canada has a word for them, kunlangeta (Seabrook, 2008). An anthropologist once asked a member of the tribe what the group would do with a kunlangeta, and he said, “Somebody would have pushed him off the ice when nobody else was looking.” Psychopaths are feared and detested everywhere.

In the popular imagination, and in plenty of horror movies and thrillers, psychopaths come in four varieties: corporate villains like Bernie Madoff, who swindled people out of billions of dollars in a Ponzi scheme that lasted many years; con artists, who are charming and charismatic hucksters; serial killers; and lifelong criminal offenders. In a thorough review for the journal Psychological Science in the Public Interest, a blue-ribbon team of investigators has separated myths about psychopaths from what the evidence shows (Skeem et al., 2011).

First, they reported what psychopathy is not: (1) It is not the same as being violent and sadistic. Many psychopaths have no criminal record or history of violence, and many criminals and rule violators are not psychopaths (Poythress et al., 2010). (2) It is not the same as being “psychotic.” Psychopaths are not delusional, irrational, out of touch with reality, or unaware of the consequences of their actions; they just don't care about those consequences. (3) The belief that psychopaths are “born, not made,” appears to be wrong. There seem to be several routes to psychopathy and any genetic predispositions interact with environmental influences. (4) The belief that “psychopaths cannot change their spots” is, surprisingly, also wrong. Some children and adults who score high on measures of psychopathy can indeed change with intensive treatment (Polaschek, 2014).

Moreover, psychopathy itself is not a single entity, like appendicitis; it involves a cluster of characteristics (Patrick, Fowles, & Krueger, 2009). Of these, two are central: First, psychopaths are fearless, unconcerned about being caught and punished for their misdeeds; this gives them a high tolerance for danger, risk, and thrill-seeking. Second, they lack empathy for others and remorse for their harmful acts. As a result, they often behave irresponsibly and treat animals and other people with great cruelty. They exploit and deceive others without flinching, and are callous and coldhearted.

Something certainly seems to be amiss in the emotional wiring of psychopaths, the wiring that allows all primates, not just human beings, to feel connected to others of their kind. The psychopath's reduced ability to feel emotional arousal suggests some aberration in the central nervous system (Hare, 1965, 1996; Lykken, 1995; Raine et al., 2000). Most psychopaths do not respond physiologically to the threat of punishment the way other people do, which may be why they can behave fearlessly in situations that would scare others to death. Normally, when a person is anticipating danger, pain, or punishment, the electrical conductance of the skin changes, a classically conditioned response that indicates anxiety or fear. But psychopaths are slow to develop such responses, which suggests that they have difficulty feeling the anxiety necessary for learning that their actions will have unpleasant consequences (Lorber, 2004; see Figure 15.2). Their lack of empathy for others also seems to have a physiological basis. When psychopaths are shown pictures of people crying and in distress, their skin conductance barely shifts, in contrast to that of nonpsychopaths, which shoots up (Blair et al., 1997).

Psychopaths also have difficulty identifying expressions of fear. Recently, clinical scientists have developed ways of measuring callousness and unemotionality in children, central dispositions that can develop into adult psychopathy (Bedford et al., 2015; Frick & Viding, 2009). Young children with these traits cannot correctly decode fear expressions in the faces, voices, or gestures of other people. They don't feel fear themselves or “get” fear in others, and as a result they may fail to respond to efforts by their parents and other adults to socialize them—and thus fail to develop a conscience (Sylvers, Brennan, & Lilienfeld, 2011).

No one yet knows for sure the origins of psychopathy. Whatever the possible genetic or biological reasons for the flaws in their “emotional wiring,” the world they live in plays a big role also. A culture that rewards ruthless behavior in work and politics will generate many “snakes in suits,” and a culture that rewards the slaughter of innocents for purposes of political or religious genocide will generate many cases of heartlessness and lack of empathy.