The Better Angels of Our Nature: Why Violence Has Declined (134 page)
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Authors: Steven Pinker
Tags: #Sociology, #Psychology, #Science, #Amazon.com, #21st Century, #Crime, #Anthropology, #Social History, #Retail, #Criminology
BOOK: The Better Angels of Our Nature: Why Violence Has Declined
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In previous sections we have caught glimpses of what the hot and cool systems might be: the limbic system (whose major parts are exposed in figure 8–2) and the frontal lobes (seen in figure 8–3). The limbic system includes the Rage, Fear, and Dominance circuits that run from the midbrain through the hypothalamus to the amygdala, together with the dopamine-driven Seeking circuit that runs from the midbrain through the hypothalamus to the striatum. Both have two-way connections to the orbital cortex and other parts of the frontal lobes, which, as we saw, can modulate the activity of these emotional circuits, and which can come between them and the control of behavior. Can we explain self-control as a tug of war between the limbic system and the frontal lobes?
In 2004 the economists David Laibson and George Loewenstein teamed up with the psychologist Samuel McClure and the neuroimager Jonathan Cohen to see if the paradox of myopic discounting could be explained as a give-andtake between two brain systems: as they put it, a limbic grasshopper and a frontal lobe ant.
84
Participants lay in a scanner and chose between a small reward, such as five dollars, which would be available in the nearish future, and a larger reward, such as forty dollars, which would only be available several weeks later. The question was, did the brain treat the choice differently depending on whether it was “$5 now versus $40 in two weeks” or “$5 in two weeks versus $40 in six weeks”? The answer was that it did. Choices that dangled the possibility of immediate gratification in front of a participant lit up the striatum and the medial orbital cortex. All the choices lit up the dorsolateral prefrontal cortex, the part of the frontal lobes involved in cooler, more cognitive calculations. Even better, the neuroimagers could literally read the participants’ minds. When their lateral prefrontal cortex was more active than their limbic regions, the participants held off for the larger-later reward; when the limbic regions were as active or more active, they succumbed to the smaller-sooner one.
84
Participants lay in a scanner and chose between a small reward, such as five dollars, which would be available in the nearish future, and a larger reward, such as forty dollars, which would only be available several weeks later. The question was, did the brain treat the choice differently depending on whether it was “$5 now versus $40 in two weeks” or “$5 in two weeks versus $40 in six weeks”? The answer was that it did. Choices that dangled the possibility of immediate gratification in front of a participant lit up the striatum and the medial orbital cortex. All the choices lit up the dorsolateral prefrontal cortex, the part of the frontal lobes involved in cooler, more cognitive calculations. Even better, the neuroimagers could literally read the participants’ minds. When their lateral prefrontal cortex was more active than their limbic regions, the participants held off for the larger-later reward; when the limbic regions were as active or more active, they succumbed to the smaller-sooner one.
As the front-heavy brain in figure 8–3 reveals, the frontal lobes are massive structures with many parts, and they carry out self-control of several kinds.
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The rearmost margin, which abuts the parietal lobe, is called the motor strip, and it controls the muscles. Just in front of it are premotor areas that organize motor commands into more complex programs; these are the regions in which mirror neurons were first discovered. The portion in front of them is called the prefrontal cortex, and it includes the dorsolateral and orbital/ventromedial regions we have already encountered many times, together with the frontal pole at the tip of each hemisphere. The frontal pole is sometimes called “the frontal lobe of the frontal lobe,” and together with the dorsolateral prefrontal cortex, it is active when people choose a large late reward over a smaller imminent one.
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The rearmost margin, which abuts the parietal lobe, is called the motor strip, and it controls the muscles. Just in front of it are premotor areas that organize motor commands into more complex programs; these are the regions in which mirror neurons were first discovered. The portion in front of them is called the prefrontal cortex, and it includes the dorsolateral and orbital/ventromedial regions we have already encountered many times, together with the frontal pole at the tip of each hemisphere. The frontal pole is sometimes called “the frontal lobe of the frontal lobe,” and together with the dorsolateral prefrontal cortex, it is active when people choose a large late reward over a smaller imminent one.
86
Traditional neurologists (the doctors who treat patients with brain damage rather than sliding undergraduates into scanners) were not surprised by the discovery that it is the frontal lobes that are most involved in self-control. Many unfortunate patients end up in their clinics because they discounted the future too steeply and drove without a seat belt or bicycled without a helmet. For the small immediate reward of getting on the road a second sooner or feeling the wind in their hair, they gave up a large later reward of walking away from an accident with their frontal lobes intact. It’s a bad bargain. Patients with frontal lobe damage are said to be stimulus-driven. Put a comb in front of them, and they will immediately pick it up and comb their hair. Put food in front of them, and they will put it in their mouths. Let them go into the shower, and they won’t come out until they are called. Intact frontal lobes are necessary to liberate behavior from stimulus control—to bring people’s actions into the service of their goals and plans.
In a collision with a hard surface, the frontal lobe bangs against the front of the skull and is damaged indiscriminately. Phineas Gage’s freak accident, which sent a spike cleanly up through his orbital and ventromedial cortex and largely spared the lateral and frontmost parts, tells us that different parts of the frontal lobes implement different kinds of self-control. Gage, recall, was said to have lost the equilibrium “between his intellectual faculties and animal propensities.” Neuroscientists today agree that the orbital cortex is a major interface between emotion and behavior. Patients with orbital damage, recall, are impulsive, irresponsible, distractible, socially inappropriate, and sometimes violent. The neuroscientist Antonio Damasio attributes this syndrome to the patients’ insensitivity to emotional signals. He has shown that when they gamble on cards with different odds of gaining and losing money, they don’t show the cold sweat that normal people experience when they bet on a card with ruinous odds.
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This emotionally driven self-control—what we might call apprehension—is evolutionarily ancient, as shown by the well-developed orbital cortex in mammals such as rats (see figure 8–1).
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This emotionally driven self-control—what we might call apprehension—is evolutionarily ancient, as shown by the well-developed orbital cortex in mammals such as rats (see figure 8–1).
But there are also cooler, more rule-driven forms of self-control, and they are implemented in the outer and frontmost parts of the frontal lobe, which are among the parts of the brain that expanded the most in the course of human evolution.
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We have already seen that the dorsolateral cortex is engaged in rational calculation of costs and benefits, as in the choice between two delayed rewards, or in the choice between diverting a runaway trolley onto a side track with a single worker or letting it proceed to the main track with five.
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The frontal pole sits even higher in the chain of command, and neuroscientists credit it with our suppleness in negotiating the competing demands of life.
90
It is engaged when we multitask, when we explore a new problem, when we recover from an interruption, and when we switch between daydreaming and focusing on the world around us. It is what allows us to branch to a mental subroutine and then pop back up to the main thing we were trying to accomplish, as when we interrupt ourselves while cooking to run to the store to get a missing ingredient, and then resume the recipe when we return. The neuroscientist Etienne Koechlin summarizes the functioning of the frontal lobe in the following way. The rearmost portions respond to the
stimulus
; the lateral frontal cortex responds to the
context;
and the frontal pole responds to the
episode
. Concretely, when the phone rings and we pick it up, we are responding to the stimulus. When we are at a friend’s house and let it ring, we are responding to the context. And when the friend hops into the shower and asks us to pick up the phone if it rings, we are responding to the episode.
88
We have already seen that the dorsolateral cortex is engaged in rational calculation of costs and benefits, as in the choice between two delayed rewards, or in the choice between diverting a runaway trolley onto a side track with a single worker or letting it proceed to the main track with five.
89
The frontal pole sits even higher in the chain of command, and neuroscientists credit it with our suppleness in negotiating the competing demands of life.
90
It is engaged when we multitask, when we explore a new problem, when we recover from an interruption, and when we switch between daydreaming and focusing on the world around us. It is what allows us to branch to a mental subroutine and then pop back up to the main thing we were trying to accomplish, as when we interrupt ourselves while cooking to run to the store to get a missing ingredient, and then resume the recipe when we return. The neuroscientist Etienne Koechlin summarizes the functioning of the frontal lobe in the following way. The rearmost portions respond to the
stimulus
; the lateral frontal cortex responds to the
context;
and the frontal pole responds to the
episode
. Concretely, when the phone rings and we pick it up, we are responding to the stimulus. When we are at a friend’s house and let it ring, we are responding to the context. And when the friend hops into the shower and asks us to pick up the phone if it rings, we are responding to the episode.
Impulsive violence could result from malfunctions in any of these levels of self-control. Take the violent punishment of children. Modern Western parents who have internalized norms against violence might have an automatic, almost visceral aversion to the thought of spanking their children, presumably enforced by the orbital cortex. Parents in earlier times and other subcultures (such as mothers who say, “Wait till your father gets home!”) might modulate the spanking depending on how serious the infraction is, whether they are at home or in a public space, and, if they are home, whether there are guests in the house. But if they are weak in self-control, or are inflamed by what they see as egregious naughtiness, they might lose their tempers, which means that the Rage circuit shakes free of frontal lobe control, and they thrash the child in a way they might regret later.
Adrian Raine, who previously showed that psychopaths and impulsive murderers have a small or unresponsive orbital cortex, recently carried out a neuroimaging experiment that supports the idea that violence arises from an imbalance between impulses from the limbic system and self-control from the frontal lobes.
91
He scanned a sample of wife-batterers as they tried to ignore the meanings of printed words for negative emotions such as
anger, hate, terror,
and
fear
and just name the color in which they were printed (a test of attention called the Stroop task). The batterers were slowed down in naming the colors, presumably because their background anger made them hypersensitive to the negative emotions the words spelled out. And compared to the brains of normal people, who can examine the print without getting distracted by the words’ meanings, the batterers’ limbic structures were more active (including the insula and striatum), while their dorsolateral frontal cortex was less active. We may surmise that in the brains of impulsive assailants, aggressive impulses from the limbic system are stronger, and the self-control exerted by the frontal lobes is weaker.
91
He scanned a sample of wife-batterers as they tried to ignore the meanings of printed words for negative emotions such as
anger, hate, terror,
and
fear
and just name the color in which they were printed (a test of attention called the Stroop task). The batterers were slowed down in naming the colors, presumably because their background anger made them hypersensitive to the negative emotions the words spelled out. And compared to the brains of normal people, who can examine the print without getting distracted by the words’ meanings, the batterers’ limbic structures were more active (including the insula and striatum), while their dorsolateral frontal cortex was less active. We may surmise that in the brains of impulsive assailants, aggressive impulses from the limbic system are stronger, and the self-control exerted by the frontal lobes is weaker.
Most people, of course, are not so lacking in self-control that they ever lash out in violence. But among the nonviolent majority some people have more self-control than others. Aside from intelligence, no other trait augurs as well for a healthy and successful life.
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Walter Mischel began his studies of delay of gratification (in which he gave children the choice between one marshmallow now and two marshmallows later) in the late 1960s, and he followed the children as they grew up.
93
When they were tested a decade later, the ones who had shown greater willpower in the marshmallow test had now turned into adolescents who were better adjusted, attained higher SAT scores, and stayed in school longer. When they were tested one and two decades after that, the patient children had grown into adults who were less likely to use cocaine, had higher self-esteem, had better relationships, were better at handling stress, had fewer symptoms of borderline personality disorder, obtained higher degrees, and earned more money.
92
Walter Mischel began his studies of delay of gratification (in which he gave children the choice between one marshmallow now and two marshmallows later) in the late 1960s, and he followed the children as they grew up.
93
When they were tested a decade later, the ones who had shown greater willpower in the marshmallow test had now turned into adolescents who were better adjusted, attained higher SAT scores, and stayed in school longer. When they were tested one and two decades after that, the patient children had grown into adults who were less likely to use cocaine, had higher self-esteem, had better relationships, were better at handling stress, had fewer symptoms of borderline personality disorder, obtained higher degrees, and earned more money.
Other studies with large samples of adolescents and adults have documented similar payoffs. Adults can wait indefinitely for two marshmallows, but as we have seen, they can be given equivalent choices such as “Would you rather have five dollars now or forty dollars in two weeks?” Studies by Laibson, Christopher Chabris, Kris Kirby, Angela Duckworth, Martin Seligman, and others have found that people who opt for the later and larger sums get higher grades, weigh less, smoke less, exercise more, and are more likely to pay off their credit card balance every month.
94
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Baumeister and his collaborators measured self-control in a different way.
95
They asked university students to divulge their own powers of self-control by rating sentences such as these:
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They asked university students to divulge their own powers of self-control by rating sentences such as these:
I am good at resisting temptation.
I blurt out whatever is on my mind.
I never allow myself to lose control.
I get carried away by my feelings.
I lose my temper too easily.
I don’t keep secrets very well.
I’d be better off if I stopped to think before acting.
Pleasure and fun sometimes keep me from getting work done.
I am always on time.
After adjusting for any tendency just to tick off socially desirable traits, the researchers combined the responses into a single measure of habitual self-control. They found that the students with higher scores got better grades, had fewer eating disorders, drank less, had fewer psychosomatic aches and pains, were less depressed, anxious, phobic, and paranoid, had higher self-esteem, were more conscientious, had better relationships with their families, had more stable friendships, were less likely to have sex they regretted, were less likely to imagine themselves cheating in a monogamous relationship, felt less of a need to “vent” or “let off steam,” and felt more guilt but less shame.
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Self-controllers are better at perspective-taking and are less distressed when responding to others’ troubles, though they are neither more nor less sympathetic in their concern for them. And contrary to the conventional wisdom that says that people with too much self-control are uptight, repressed, neurotic, bottled up, wound up, obsessive-compulsive, or fixated at the anal stage of psychosexual development, the team found that the more self-control people have, the better their lives are. The people at the top of the scale were the mentally healthiest.
96
Self-controllers are better at perspective-taking and are less distressed when responding to others’ troubles, though they are neither more nor less sympathetic in their concern for them. And contrary to the conventional wisdom that says that people with too much self-control are uptight, repressed, neurotic, bottled up, wound up, obsessive-compulsive, or fixated at the anal stage of psychosexual development, the team found that the more self-control people have, the better their lives are. The people at the top of the scale were the mentally healthiest.
Are people with low self-control more likely to perpetrate acts of violence? Circumstantial evidence suggests they are. Recall from chapter 3 the theory of crime (championed by Michael Gottfredson, Travis Hirschi, James Q. Wilson, and Richard Herrnstein) in which the people who commit crimes are those with the least self-control.
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They opt for small, quick, ill-gotten gains over the longer-term fruits of honest toil, among them the reward of not ending up in jail. Violent adolescents and young adults tend to have a history of misconduct at school, and they tend to get into other kinds of trouble that bespeak a lack of self-control, such as drunk driving, drug and alcohol abuse, accidents, poor school performance, risky sex, unemployment, and nonviolent crimes such as burglary, vandalism, and auto theft. Many violent crimes are strikingly impulsive. A man will walk into a convenience store for some cigarettes and on the spur of the moment pull out a gun and rob the cash register. Or he will react to a curse or insult by pulling out a knife and stabbing the insulter.
97
They opt for small, quick, ill-gotten gains over the longer-term fruits of honest toil, among them the reward of not ending up in jail. Violent adolescents and young adults tend to have a history of misconduct at school, and they tend to get into other kinds of trouble that bespeak a lack of self-control, such as drunk driving, drug and alcohol abuse, accidents, poor school performance, risky sex, unemployment, and nonviolent crimes such as burglary, vandalism, and auto theft. Many violent crimes are strikingly impulsive. A man will walk into a convenience store for some cigarettes and on the spur of the moment pull out a gun and rob the cash register. Or he will react to a curse or insult by pulling out a knife and stabbing the insulter.
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