The Anatomy of Violence (29 page)

Moving from the
frontal control region of the brain to the deeper
limbic emotional areas, we are seeing signs that something is fundamentally wrong with the brain’s anatomy in offenders. Their anatomical anomalies are not restricted to these brain regions. If we move just a bit further behind the amygdala, we come to the hippocampus, a critical region shaped like a sea horse that’s involved in a variety of functions ranging from memory to spatial ability. Here too we find a structural abnormality in psychopaths, but of an unusual kind.

We saw earlier how hippocampal functioning was impaired in offenders. That functional abnormality is likely caused by structural abnormalities that have been observed in a wide number of studies. In one group of psychopaths that we studied we found that the right hippocampus was significantly bigger than the left.
⁷⁵
This structural asymmetry is true in normal people too, but it is much stronger in psychopaths. Interestingly, we found this very same asymmetry in our sample of murderers, this time in terms of function.
⁷⁶

What causes this abnormality is not known for certain, although there are some interesting clues. If rat pups are moved around
early in
life into different “homes,” they develop an exaggerated hippocampal asymmetry: the right hippocampus grows to be bigger than the left.
⁷⁷
We found in our interviews with psychopaths that they had been bounced around from home to home much more often than controls in their first eleven years of life—more than seven different homes in psychopaths compared with three in controls.

Another factor is fetal
alcohol exposure. When the brains of children suffering from
fetal alcohol syndrome are scanned, it is found that the right-greater-than-left hippocampal volume that is found in normal controls is exaggerated by 80 percent.
⁷⁸
If you have read casebooks on killers, these two clues will be familiar to you. The early lives of
violent offenders are invariably characterized by broken homes, substance-abusing and neglectful mothers, and instability. These factors taken together could be the environmental cause of the hippocampal abnormality we see in psychopaths.

Other researchers have similarly observed overall smaller hippocampal volumes in violent alcoholics.
⁷⁹
In psychopaths, structural depressions have been found in areas of the hippocampus that play a role in autonomic responses and
fear conditioning,
⁸⁰
while we have similarly observed volume reductions in the
hippocampus in murderers from
China.
⁸¹

What does the hippocampus do apart from helping you remember your boyfriend’s birthday and how to get to Walmart from the freeway exit? The hippocampus patrols the dangerous waters of emotion. For one thing, it is critically important in associating a specific place with punishment—something that helps fear conditioning.
⁸²
Just think back to where you were when a bad thing happened—that’s your hippocampus helping you remember. So, like the amygdala, it plays a key role in fear conditioning and other forms of learning that partly constitute our conscience—the guardian angel of
behavior. Criminals have clear deficits in these areas. The hippocampus is also a key structure in the limbic circuit that regulates emotional behavior.
⁸³
From
animal research we know that the hippocampus regulates aggression through projections to the
midbrain periaqueductal
gray and the perifornical lateral
hypothalamus. These are deep subcortical structures that are
highly important in regulating both
defensive and
reactive aggression as well
as predatory attack.
⁸⁴
For example, rats with hippocampal lesions at birth show increased aggressive behavior in adulthood.
⁸⁵
These hippocampal abnormalities could be linked to the
cavum septum pellucidum abnormality we just discussed, because the septum pellucidum forms part of the septo-hippocampal system, a
brain circuit that researcher
Joe Newman has argued plays a role in psychopathy.
⁸⁶

The hippocampus and
amygdala are located in the inner side of your temporal cortex. But that’s not right in the middle of your brain. What is in the middle is the
corpus callosum—a colossal body of over 200 million nerve fibers that connect your two cerebral hemispheres. These fibers—the
corona radiata—radiate out from the very center of your brain to the outer areas of your cerebral hemispheres, interconnecting many different brain regions. We measured the volume of the corpus callosum and its corona radiata and found that this volume is much bigger in psychopaths with antisocial personality disorder. It was also longer. And thinner too. A long, thin body of
white matter. It’s as if there is too much connectivity in the brains of psychopaths—too much cross talk between the two hemispheres.

What do we make of this? Although we often think of psychopaths as antisocial villains with a lot of negative characteristics, they’re actually a lot of fun. They have a lot of positive features, especially on the surface. In particular, many psychopaths have the gift of gab. They are very glib, very charming, very good con artists who can convince you of almost anything.
Robert Hare—regarded by many as one of the world’s leading researchers on psychopathy—has demonstrated, using something called the
dichotic listening task,
⁸⁷
that psychopaths are less “lateralized” for language.
⁸⁸
We found the same thing in juvenile psychopaths.
⁸⁹
What does this mean? In many of us, the left hemisphere is largely responsible for language processing—language is strongly lateralized to the left hemisphere. But in psychopaths it’s more of a mix of both left and right hemispheres. This might be why they seem to be so adept in their
verbal skills. They have two hemispheres—not one—that they can utilize for language processing. This in turn could be due to a larger, better communicating corpus callosum.

We have to remember that psychopaths are a special group of criminal offenders and that we cannot say the same thing about run-of-the-mill violent offenders. But whichever way you look at it, psychopaths appear to be literally “wired” differently from the rest of us.

We have moved anatomically from the surface of the brain—the cortex—into the deeper brain regions—the subcortex. Now let’s continue our subterranean tour to another deep-brain region—the
striatum. In evolutionary terms, this is an old brain structure involved in one basic function common across all species—
reward-seeking behavior. For a long time in our laboratory we have felt that
psychopathic individuals may be characterized by an oversensitivity to rewards. When there is a chance of getting the goods, they seem to go all out—even at the risk of negative consequences.

The first new study I conducted when I moved from Nottingham to
Los Angeles sought to test out this idea.
⁹⁰
I was an assistant professor. As for all assistant professors when I started out, academic life was not that easy. I was involved in studies in England and Mauritius, but the expectation was that you should also be setting up your own laboratory and conducting work independent from other investigators in order to establish your independence. You have to show that you have what it takes to go it alone.

Easier said than done. I felt lost in L.A. I didn’t have a penny for
research funds, so whatever research I did would have to be done on the cheap. One piece of luck was that I had two students who wanted to work with me
during their summer alongside with
Mary O’Brien, a senior professor’s graduate student who was interested in child antisocial behavior.

The next bit of luck was that there were a bunch of
juvenile
delinquents living just down the road from me in the Eagle Rock neighborhood of Los Angeles. I got permission from the Superior Court of California to work with them. They lived in a home as an alternative to being sentenced to a closed institution, and for these teenage boys participating in experiments with young female undergraduates from USC was not unappealing. Forty out of the forty-three kids we approached were keen to be involved in the study.

The third bit of luck was that while I had given up orange juice to save for a down payment on a home, I did have a deck of cards and some plastic poker chips. Taken together, this would be enough for my first study in L.A.

We had the mischief-makers play a game of cards that went something like this. Each card had a number on it. For half of the numbers,
selecting them would result in the gain of a poker chip—so this was a
reward card. Half of the cards, though, would result in a loss—a punishment card. Touching the card was a response. The subject could touch it to select it, or not touch it to pass. Over the course of sixty-four card plays, the subject had to make as much money as he could—to learn which cards were the winners. We assessed which of the delinquents were psychopaths based on staff ratings of their behavior and personality, and then we compared them to delinquents who were not psychopaths.

The results? My graduate student
Angela Scarpa showed that our young psychopaths showed much greater response to the reward cards than the non-psychopaths. They were hooked on rewards, confirming previous studies showing the same in adult psychopaths.
⁹¹
Our budding psychopaths actually showed better learning throughout the task too. This suggests that psychopaths can learn—as long as you use rewards to shape their behavior. It was the first time that a reputable journal had published a study on “juvenile psychopaths.”
⁹²
Until then, nobody liked the idea that adolescents might actually be psychopaths in the making.

Twenty years went by and we were still mulling over the findings. Could this behavioral difference translate to brain differences
in psychopaths? My graduate student
Andrea Glenn tested the idea out on our psychopaths from
temp agencies.
⁹³
The striatum is a key brain region that is associated with reward-seeking and impulsive behavior. Studies have also showed that it is involved in
stimulation-seeking behavior, persistently repeating actions that are related to rewards, and enhanced learning from reward stimuli.
^94
,
95
Sounds like psychopathic behavior, doesn’t it? We found that our psychopathic individuals showed a 10 percent
increase
in the volume of the striatum compared with controls. Results could not be explained by group differences in age, sex, ethnicity, substance or
alcohol abuse, whole brain volumes, or even socioeconomic status. They seemed pretty solid.

We reasoned that the increase in striatal size could contribute to the increase in the sensitivity of psychopaths to rewards, and consequently their incessant reward-seeking behavior. To be sure, psychopaths are not alone. We are all driven by rewards. We each want our own stuff. We want masses of money, a decent dwelling, fancy food, wonderful work, fun friends—and let’s throw in superb sex for good measure. But the difference between us and psychopaths is that we can say no when
tempted by the goodies, whereas
psychopaths just want their stuff. And they want it here, and they want it now. For them, reward is a drug that they cannot turn their backs on, and this pushes them along a path of depravity and vice.

Our findings on psychopaths did not stand alone. Increased striatal volumes have also been found in those with
antisocial personality disorder,
⁹⁶
while increased striatal functioning has been observed in violent
alcoholics
⁹⁷
as well as
aggressive adolescents and adults.
⁹⁸
Furthermore, in 2010, just two months after we had published our study touting this neural basis to reward-seeking behavior in psychopaths, a functional brain-imaging study came out from another research group with essentially the same argument.
⁹⁹
People in the community scoring higher on impulsive, antisocial features of psychopathy were found to be hypersensitive to rewards, this time due to excessive activation of another subcortical brain area when anticipating a reward—the
nucleus accumbens. This brain area is strongly involved in the brain’s
dopamine-reward circuitry, which we discussed in
chapter 2
. Antisocial individuals really do appear to be turned on more than the rest of us by stuff that takes their fancy.

Rewards are important to offenders, and to them money doesn’t just talk—it swears. It’s very salient to them. A full 45 percent of psychopaths are
motivated by money in the crimes they perpetrate.
¹⁰⁰
Studies also show that it takes less money to push psychopaths into violating moral principles than non-psychopaths.
¹⁰¹
But more troublingly, aggressive,
conduct-disordered kids show increased activity of the striatum when they view images of other people in pain.
¹⁰²
Somewhat sickeningly, these aggressive children seem to enjoy seeing people in pain, not unlike a number of serial killers who cruelly
torture and maim their victims. Combine this characteristic with
frontal-lobe dysfunction and the disinhibited behavior it causes, and you have a cocktail for criminal violence.

However we interpret structural deficits of the amygdala, hippocampus,
corpus callosum, and striatum in psychopathic and antisocial offenders, one thing stands out. These structural abnormalities are likely not the result of some discrete disease process or obvious trauma. Such causes would if anything result in overall volume
reductions
to these structures. Our findings are much more complex than that. The right hippocampus is
larger
than the left in psychopaths. The striatum is
larger
. The corpus callosum also has a
bigger
volume. And the
corpus callosum is not only
longer
in psychopaths than in controls, it’s also
thinner
. So what’s the explanation here? It is likely that this shape distortion is
neurodevelopmental in nature. The striatum and its associated structures—the
caudate and
lenticular nuclei—are enlarged, not shrunken. These brain structures are growing abnormally in psychopaths during infancy and childhood. Again we get back to the idea that there is—at least in part—a
neurodevelopmental basis
to psychopathic and antisocial behavior. A
born criminal? Not really. But a baby whose brain is compromised in its development? Quite likely.