The Anatomy of Violence Read online

  I take our instrumental proactive murderers as a model for serial killers, on whom we know very little scientifically. If I could perform brain scans on a significant group of serial killers, I might expect a brain profile similar to our proactively aggressive killers—a hotbed of seething limbic activation bubbling under the good prefrontal functioning that allows them to carefully plan their actions. Yet even within this pack of serial killers, make no mistake—there will inevitably be several shades of gray lurking in the etiological shadows.

  THE FUNCTIONAL NEUROANATOMY OF MURDEROUS MINDS

  We’ve seen that the prefrontal cortex is critical in regulating and controlling both behavior and emotion. We’ve also seen that excessive subcortical activity may fuel the heightened emotion that we see in our violent offenders. We could stop there in our mapping of the mind of the murderer. We have the essence here in a nutshell. Yet as I readily acknowledged above, the scientific reality would be that we are being overly simplistic. We get back to the complexity of homicide, psychopathy, and criminal offending, and the inevitability that any attempt to explain and understand such behavior through functional neuroanatomy—the workings of the brain—is going to be enormously complex. Here I’ll give you just a piece of the exciting neuroanatomical action that is taking place today in our probing of the murderous mind.

  Moving from the front of the brain, where we have been focusing, to the relatively less explored posterior part, we’ll start with the angular gyrus—area 39 in the map created by the German anatomist Korbinian Brodmann in 1909. The angular gyrus lies in the inferior, or lower, half of the parietal lobe, above the superior temporal cortex, and in front of the visual cortex. It is consequently in a prime position in the brain, lying at the junction of three of the four major lobes—the parietal, the temporal, and the occipital cortices. It connects and integrates information from many modalities—visual, auditory, somatosensory, vestibular—in order to perform complex functions. It lies on the surface of the brain. Find the top of your ear with your fingers and move them up a couple of inches—1.5 inches behind that spot is about where the angular gyrus lies.

  We imaged the angular gyrus in our murderers and found significantly lower glucose metabolism in this structure than in those of the controls. In Sweden, researchers also found reduced cerebral blood flow in this area of the brain in impulsive, violent criminals.27 Other researchers have argued for angular gyral dysfunction in violent offenders as well.28

  How might dysfunction of the angular gyrus translate to violence and offending? The angular gyrus is one of the latest areas of the brain to develop, and so, not surprisingly, the abilities it governs are complex and sophisticated. Unlike the visual cortex, which comes online immediately for the newborn infant, the angular gyrus subserves functions that include reading and arithmetic, abilities that as we know do not start early in life, but develop much later in childhood. So, for example, reductions in glucose metabolism in the left angular gyrus have been associated with reduced verbal ability,29 while damage to this region in neurological patients results in problems with reading and arithmetic30—complex functions that involve integration of information across multiple domains. Writing ability is also affected in a subtle way. For example, letters may be missing or duplicated, or be widely spaced. Punctuation is off, and capital letters may be disregarded.

  So if the angular gyrus is not functioning well, then a child’s reading, writing, and arithmetic are going to suffer—the three R’s that are the foundations of scholastic performance. What do we know about violent offenders? They do poorly at school. If you do poorly at school, you’ll have a problem getting a job. You won’t get as much money as you’d like. You’ll then be more likely to use violence to get what you want in life—things you cannot get because of your educational failure. The root cause may be brain-based, but the path to violence may well lie along school and occupational failure—a social/educational process.

  The hippocampus and its surrounding area, the parahippocampal gyrus, is another brain region that is disturbed in offenders. The hippocampus lies just behind the amygdala and its Latin name means sea horse. We’ve touched on this area above in connection with our sample of murderers, and other researchers are also finding that offenders have functional disturbances in this brain region. One study on antisocial, conduct-disordered boys from London showed reduced function of the hippocampus during an attention task.31 In Sweden, the neuroscientist Henrik Soderstrom found reduced hippocampal functioning to be associated with higher psychopathy scores in violent offenders.32 In the United States, Kent Kiehl has argued that the parahippocampal gyrus contributes to symptoms of psychopathy.33 Researchers in Germany led by Jürgen Müller also found reduced parahippocampal functioning in adult psychopaths,34 while Daniel Amen in California found the same finding in impulsive murderers.35

  We need to ask why hippocampal impairment would make an individual more likely to offend. For one thing, it makes up part of the emotional limbic system. We know in turn that psychopaths and other offenders have abnormal emotional responses. The hippocampus is also part of the neural network that forms the basis for the processing of socially relevant information, and it is involved in recognizing and appraising objects. Disruption to such a system could in part relate to the socially inappropriate behavior shown by some violent individuals, as well as the misrecognition and misappraisal of ambiguous stimuli in social situations that can result in violent encounters.36

  The hippocampus is critical for learning and memory. It’s one of the first areas to go in people with Alzheimer’s disease. With my longtime colleagues Rolf and Magda Loeber in Pittsburgh I studied the ability of schoolboys to remember both verbal material and nonverbal, visuospatial material. The result? Boys who had been persistently antisocial from the age of six to sixteen as rated by their parents and teachers did more poorly on these hippocampal memory tasks than controls.37

  We also know that the hippocampus plays a role in fear conditioning, and as we’ll see in a later chapter, antisocial and psychopathic individuals have a particular deficit in this form of learning. Psychopaths are fearless individuals, as are many other violent offenders. It’s worth noting that researchers from Italy and Finland have found a structural abnormality in the hippocampus of psychopaths, which plays an important role in fear conditioning and emotional responding.38

  Yet there’s more to the hippocampus than memory and ability. It is a key component in the limbic circuit that regulates emotional behavior,39 and it has been implicated in aggressive, antisocial behavior in both animals and humans. In animals, it regulates aggression through its connections to deep structures in the middle of the brain, including the lateral hypothalamus and what’s called the periaqueductal gray, structures important in controlling both defensive rage attack and predatory attack.40 So a poorly functioning hippocampus will be of little help to either an offender who is beginning to fly off the handle in the first stage of an argument, or one who is seeking revenge.

  Another brain area that is believed to be dysfunctional in offenders is the posterior cingulate, lying more toward the rear of the head and deep inside the middle of the brain. This region has been found to be poorly functioning in adult criminal psychopaths,41 conduct-disordered boys,42 and aggressive patients.43 Because this brain region is also important in the recall of emotional memories44 and the experiencing of emotions,45 a disturbance to this area will likely result in a disturbance in emotion, including causing anger. We also know that the posterior cingulate is involved in self-referential thinking—the ability to reflect back on oneself and understand how one’s behavior can affect others.46 So if a psychopath fails to understand how his actions can harm others, this could help explain his thoughtless, antisocial acts and his failure to accept responsibility for his actions.

  A NEW EXCUSE FOR WIFE ABUSE?

  Killing is one thing. Striking your wife across the face is another. The trouble with research like mine on murder is that killing is very rare
. What about more common acts of serious violence like spousal abuse?

  Of course, I’m not saying that spousal abuse is trivial by any means, but it’s far more common than homicide. Are spouse-abusers different from killers in brain functioning? Or can we discern similar patterns in these common-variety offenders? To help answer that question, let’s take a trip to Hong Kong.

  It’s a fantastic place. I took my family there when I was on sabbatical at Hong Kong University. People were so sweet and polite. The very first morning that I took my two young boys, Andrew and Philip, to Victoria Kindergarten in the Fortress Hill area, we were stopped in the street by a young woman. She asked if she could help hold the boys’ hands. Well, why not? So off we all marched, hand in hand to preschool, where she duly said good-bye to the boys, thanked me, and vanished into thin air amid the bustling streets.

  Strange, isn’t it? Maybe she was a nutcase, but I don’t think so. She was a smartly dressed professional. To her, my two-year-old tots were cute curiosities, decked out in their red school blazers, gray trousers, satchels, and mixed Asian-and-Caucasian faces. It was typical of the graciousness, courtesy, and respect for the family and children that Hong Kongers have.

  Yet lurking beneath that civilized façade lies the cruel visage of domestic violence. I did a survey of 622 Hong Kong undergraduate students. They were not all rich kids by any means, but they were largely from the privileged classes. You don’t expect much to have gone on in their homes in their formative years. But I nevertheless asked them how their parents dealt with conflicts before the kids were eleven—before they could turn into troublesome teenagers. Sixty-two percent had parents who would insult or swear at them, 65 percent had parents who would do or say something just to spite them, while 48 percent were slapped or spanked.

  No big deal, you’ll say, if you remember being on the receiving end of a good spanking or two as a child. Surely this happens in the best of homes. But let’s get beyond the simple stuff. Fifty-one percent went on to admit that their parents would hit them with an object. Forty percent were physically beaten. Six percent had actually been choked, while 5 percent had been deliberately burned or scalded. Seven percent had even been threatened with a knife or gun. In all cases it was their own parents perpetrating the abuse. So how often did your parents choke and burn you or put a gun to your head before you turned eleven?

  Serious domestic violence was pretty rampant even in the homes of these educated, better-off undergraduates. True base rates are likely a lot higher, since people forget what really happened after ten years. Plus, you never want to admit—even to yourself—that you had parents bordering on the sadistic and inhuman. Some of these kids were having the living daylights beaten out of them—some repeatedly—behind closed doors. And these are the better-off kids. Heaven knows what was happening—and still is going on—to kids from much poorer homes in Hong Kong.

  And where the kids are getting beaten, the wives are being bashed. Today it’s hard to believe, but until about 1980 spousal abuse was hidden under the carpet at home.47 A man who gave his wife a belting was not considered a criminal; such treatment was part and parcel of everyday married life. Even after the recent criminalization of spousal abuse, wife battering is still rife. The prevalence of spousal abuse each year is approximately 13 percent in the United States, with an estimated 2 million to 4 million victims a year.48 It accounts for about half of all female homicides and is a leading cause of injury to developing fetuses.49 It’s a shocking, disgraceful, criminal offense, and yet it’s all too common and frequently tolerated in some households.

  Let’s face up to these spouse-abusers. If we can look beyond their eyes and into their brains, do these men also have a dysfunctional cortex? They batter women, but is that because they have battered brains?

  Tatia Lee is a brilliantly creative clinical neuroscientist at Hong Kong University with a penchant for sailing into uncharted waters. She conducted some of the very first brain-imaging work on lie detection, and she was just a couple of doors down from my office during my time there in 2005. Together with her graduate student, we teamed up to test our ideas on spousal abuse. We recruited twenty-three men referred by police to social-welfare departments and psychology practices for physically abusing their wives. Our main hypothesis was that such men may overrespond to emotional stimuli, and that that may in part be a cause of their abuse. We measured their reactive and proactive aggression and also gave them two verbal and visual emotion tasks.

  The verbal task is called the emotional Stroop task. The subject is first presented with the name of a color, like “blue.” They then see an emotionally negative word like “kill,” which is either printed in blue or another color, and have to judge whether the color of the word “kill” was blue or not. The same thing is done with nonemotional words, like “change.” We then measure how long it takes them to respond. People who take longer to respond to the emotional word than to the neutral word are showing a cognitive bias to negative affect stimuli—meaning that the negative emotional nature of the word has hijacked their brain’s attention and slowed down their responses.

  In the visual task, the subjects viewed neutral pictures like a chair and also emotionally provocative pictures—things like a man holding up another man in a robbery with a gun to his head, or a man holding a woman from behind with a sharp knife across her throat. In both of these verbal and visual tasks we scanned their brain using functional magnetic resonance imaging (fMRI). Our research resulted in fourfold findings.

  First, spouse-abusers were strongly characterized by reactive aggression—where the individual responds aggressively in the face of provocation. In contrast, once we controlled for this, the spouse-abusers showed no proactive aggression. They were not using aggression in a planned, premeditated, manipulative fashion.

  Second, in the emotional Stroop task, the spouse-abusers were slower in responding to emotional words. Negative emotional stimuli were capturing their attention much more than normal.

  Third, in functional brain scans during the emotional Stroop task, our spouse-abusers showed much greater activation of the emotional amygdala to negative-emotion words, together with less activation in the regulatory prefrontal cortex.

  Fourth, when batterers saw pictures of visually threatening stimuli, they showed hyper-responding in widespread brain areas covering the occipital-temporal-parietal regions. These regions are exceptionally sensitive to the recognition of objects50 and to spatial perception.51 They indicate that batterers experience greater visual arousal when exposed to threatening stimuli.

  Putting these four findings together, a pernicious pattern unfolds. Spouse-abusers have a reactive aggressive personality that makes them more likely to lash out when provoked. Emotional words inordinately grab their attention. They are less able to inhibit the distracting emotional characteristics of stimuli, resulting in impaired cognitive performance. When presented with aggressive stimuli their brains overrespond at an emotional level and underrespond at a cognitive control level. Spouse-abusers are constitutionally different from other men.

  These neurocognitive characteristics of batterers may partly contribute to their abusive behavior. Some researchers have documented that batterers do not listen to reason, and instead emotionally react out of all proportion to a situation.52 Excessive attentional processing to a visual stimulus like a frown or a scolding voice may distract the batterer’s attention and make him misinterpret the social interchange. It could contribute to the racing thoughts, irrational behavior, and escalating negative emotion that characterize wife-batterers.53

  To my knowledge, these are the first physiological studies of any kind to show brain abnormalities in spouse-abusers when reacting to emotional stimuli, and the first to demonstrate hyperreactivity to threatening stimuli. Our findings challenge an exclusively social perspective on spousal abuse and suggest instead a neurobiological predisposition to battering. Historically, the prevailing clinical perspective has been that spousal abuse is
a conscious, deliberate, and premeditated use of power to subjugate and control the female partner for selfish instrumental gain.54 An alternative hypothesis that Tatia and I suggest is that spousal abuse has a significant brain-based reactively aggressive component.55

  Is this a newfangled excuse for wife-abuse? I’m not exactly saying that abusers are not to blame. And I’m not saying that all abusers are like this. But I do think we need to recognize that there’s more to domestic violence than the traditional feminist perspective cares to admit. Feminists argue that the cause of spousal abuse lies in a patriarchal society that sanctions men’s using physical power to control women. We argue instead that neurobiology nudges some men to overreact at home and that we need to consider a contribution by the brain to spousal abuse. Why? Because traditional treatment programs to treat spouse-abusers based on the feminist perspective simply do not work.56 We need to incorporate neurobiological perspectives into domestic-abuse treatment programs if we genuinely want to eradicate this completely unacceptable behavior of men toward women.

  THE LYING BRAIN

  So far we have been talking about people who are characterized by the media as brutes, monsters, and villains. We have been discussing despicable deeds that include murder, child rape, and wife-battering. And you may be sitting there dispassionately reflecting on how this other half lives, and what exactly makes these mean men tick.

  But what about you? What’s ticking away inside you when you perpetrate an antisocial act? Oh, so you’re not antisocial? You really think that? Well, not perhaps antisocial at the level that we have been discussing so far, but let’s turn to two arenas that will be much more familiar to your daily experience than murder and spouse-battering. You’re not perhaps so wonderful after all.