Crime Library: Criminal Minds and Methods

The Unthinkable: Children Who Kill

Violence and the Brain

Joshua Phillips
Joshua Phillips

After Joshua Phillps killed his eight-year-old neighbor and stuffed her body beneath his waterbed, he went on trial for murder.  At the time, there was a theory that violence was somehow coordinated with abnormal EEGs, or heart rhythms.  If such a correlation could be proven, then there might have been a physiological explanation for what he did.  In other words, he just followed through on what his brain ordered him to do.

However, this theory failed to pan out.  Until proven otherwise, he had nothing to blame but himself.

Nevertheless there are researchers who firmly believe that violence is clearly the product of some kind of physiological imbalance.  Some say it's almost entirely a matter of chemical interactions in the brain, while others believe that physiology and the environment are interconnected.

Debra Niehof, a neuroscientist, studied twenty years of research before she wrote The Biology of Violence.  Specifically, she asks whether violence is the result of genes or a product of the environment.  Aware that our culture has developed a resistance to blaming the body, she nevertheless offers proof that at times such is the case—yet the environment gets its share of the credit, too.  In her opinion, each factor modifies the other such that processing a situation toward the end of a violent resolution is unique to each individual.  In other words, a particular type of stimulation or overload in the brain is not necessarily going to cause violence in every instance.

"The biggest lesson we have learned from brain research," she says, "is that violence is the result of a developmental process, a lifelong interaction between the brain and the environment." 

The way this works is that the brain keeps track of our experiences through chemical codes. When we have an interaction with a new person, we approach it with a neurochemical profile influenced by attitudes that we've developed over the years about whether or not the world is safe, whether people are trustworthy, and whether we can trust our instincts in reading a stranger.

However we feel about these things sets off certain emotional reactions and the chemistry of those feelings is translated into our responses. "Then that person reacts to us, and our emotional response to their reaction also changes brain chemistry a little bit. So after every interaction, we update our neurochemical profile of the world."

The chemistry of aggression is associated with the chemistry of our attitudes and we may turn a normally appropriate response into an inappropriate response by overreaction or by directing it to the wrong person.  In other words, the person's ability to properly evaluate the situation becomes impaired.  "If a person has come to believe that the world is against them, and they are overreacting to every little provocation, these violent reactions get beyond their ability to control, because they are in survival mode."

Niehoff says that there are different patterns of violent behavior and certain physiological differences are associated with each pattern. For example:

  1. Over-reactive patterns – they are hyperactive with a short attention span.  The challenge is to get them to slow down and engage conscious thinking processes.
  2. Under-reactive pattern – they have trouble developing empathy; have lower galvanic skin responses and a lower metabolic rate; and fail to attach emotion to their behavior.  The challenge is to keep them connected and to reinforce their learning of appropriate social behaviors.

Applying this idea to bullying, which has been at the heart of much of the school violence in the past few years, Niehoff says  "Your child is spending several hours almost every day in that environment, and to be on the receiving end of violence on a daily basis is very destructive. I think that schools need to be more aware of the subtle bullying that goes on. We're not going to stop all aggression between kids, but we ought to be more aware of the tormenting, teasing, badgering, and threatening – and should step in early to intervene."

Around 30 percent of school children are involved in bullying incidents.  Each time a bully acts aggressively, it affects the victim's brain chemistry and reinforces the idea that the world isn't safe.  The resulting physiological response is to protect oneself and become hyper-alert to threat. The bully, too, gets reinforced in physiological aggression, especially against kids who are isolated.  Yet the more they get picked on, the more isolated they get, triggering yet another cycle of bullying.

It's important to understand that violence has no single cause and should not be treated as if it does.  It can arise from any of a number of parts of the physiological structure.  Everything we encounter or experience has the potential to affect us, and there is no single factor to target for blame.  Violence is the result of a complex feedback loop, but it's one that can be broken.

Essentially, says Niehoff, the past informs the present but does not have to predict the future. "Biology is not destiny."  The brain is flexible and can relearn patterns by integrating new experiences.  We have the tools to reduce violence by creating a safe and caring environment.

What about Girls?

Jessica Holtmeyer
Jessica Holtmeyer

In Clearfield, Pennsylvania in 1998, Jessica Holtmeyer, 16, made plans with a gang of friends to run away to Florida.  They decided on a night and had a sleepover.  They also invited Kimberly Dotts, 15, who was learning-disabled and badly wanted to be friends with this group.  As they discussed their plans out in the woods, they began to get paranoid that Kimberly would snitch on them after they left. While five kids watched, Jessica and a boy named Aaron Straw put a noose over Kimberly's neck and slung the other end over a tree branch.  Then they yanked the rope, pulling on it until Kimberly's convulsing body went limp.  They let her go, but then hanged her again.  When they lowered her to the ground, she was still gasping for breath, so Jessica grabbed a large rock to finish her off.  Then she laughed and said that she wanted to cut the dead girl into pieces and take a finger as a souvenir.

Straw claimed that he thought they were just trying to scare her, and for the first time he saw something in Jessica that disturbed him: "It was like a side of her I didn't see before.  Like she didn't care about nothing.

While such episodes do occur, and girls who participate can be just as callous and brutal as boys, it's nevertheless true that only ten to fifteen percent of murders involve females of any age, and most are adults.  Among the reasons girls give for killing are revenge against an abuser, self-protection, or to get rid of a witness to another crime.  Few are senseless, and girls rarely kill strangers.  Mostly they turn on a family member and often it's their own child.  It's also clear that girls rarely commit a murder on their own.  Often they have accomplices or do it as part of a gang.

No one is born to be violent, but males have a greater capacity to move in that direction.  Antisocial acts are three times more common among males, and males have a greater tendency to develop violence-based sexual fantasies that then affect their physiology.  Nevertheless, it's not all about hormones, as many people believe.  The more complex a species is, the less of a factor hormones are in violent aggression.  In apes and humans, testosterone levels appear to have more to do with the desire to win than the desire to fight or to kill.  It's a quest for advancement, and it also provides males with a greater sensitivity to the environment.  They can match key features with specific responses, and the brain records their successes and failures.  "Testosterone was most clearly linked to aggression," Niehoff says about one study, "when the violent behavior was a reaction to an overture perceived as a threat."  Boys with higher levels were more irritable and more easily provoked, but they did not have a greater tendency to initiate violence.  

Thus, there is clearly a difference between male and female physiology, but perception and experience do play a large part in the formation of violence in either gender.

What about Thrill-killing?

While most violence occurs under provocation of some type, there is a population that initiates it for pleasure and erotic stimulation.  Some are psychotic, some are provoked by substances, and some use violence as a weapon---and are most likely to turn to it after suffering a humiliating defeat.  However, there are some killers for whom violence is the only way to satisfy their lust.  They're driven by the need for this form of arousal. 

Yet even for them, the development of these behaviors derives from a cumulative exchange between their experiences and the nervous system.  It all gets coded into the body's neurochemistry as a sort of emotional record.  The more they succeed and feel the high, the more likely it is that they will return to this behavior.

So how does all of this translate into a practical program for determining when a kid might become violent?  What signs should we be looking for?


We're Following
Slender Man stabbing, Waukesha, Wisconsin
Gilberto Valle 'Cannibal Cop'