On July 20, 2012, a heavily armed young man walked into a movie theater in Aurora, Colorado, and opened fire on the audience, killing 12 people and injuring nearly 60.
Here’s the thing: On paper, James Holmes measured up seemingly well. Intelligent, disciplined, and raised by successful parents — his father, a senior scientist; mother, a nurse. Holmes graduated from UC San Diego at the top of his class and was working towards a Ph.D. in neuroscience. It’s hard to imagine that this would be a person to carry out one of the nation’s deadliest recent massacres. But upon taking a closer look into the details of his behavior and characteristics leading up the massacre, experts agree that he does indeed fit the profile of a typical mass murderer.
Holmes has been put behind bars, but the question still lingers: What drives someone to go on such a violent rampage, indiscriminately killing innocent people? Are there clear motives behind these violent acts? Insanity, or a psychotic break? An absent conscience? Or are some people just born natural killers?
Researchers have posed the same questions and, with recent scientific advancements, have been able to note personality-based, neurological, and even genetic-based commonalities in these violent individuals. Most experts will agree that there isn’t a single determining factor that creates a mass murderer, but when multiple triggers are combined, a killer is born. Furthermore, through various studies looking at brain images and scans of murderers, psychopaths, and violent individuals, researchers are gaining leverage in mapping out the neural activity behind impulsive violence.
The human brain was designed with natural checks and balances that control our impulses and behavior and regulate our emotions. So it’s no surprise that the brain of a mass murderer has a glitch in its regulatory system which may increase the risk of impulsive violent acts.
Psychologist Richard Davidson and his colleagues at the University of Wisconsin analyzed brain-imaging data from a large, diverse group of studies done on violent individuals, including those with aggressive personality disorder, those with childhood brain injuries, and convicted murderers. Davidson’s findings showed similarities in brain activity among these more than 500 subjects.
One of the core discoveries involved abnormalities in three distinct brain regions involved in regulating emotions: the anterior cingulate cortex, the orbital frontal cortex, and the amygdala. The anterior cingulate cortex works to communicate with and recruit other brain regions in response to conflict, while the orbital frontal cortex is involved with ethical behavior, moral decision-making, and impulse control; it works to moderate and constrain our impulsive outbursts. The amygdala is involved with aggression, fear, and other emotional processing.
In many of the subjects, Davidson noted diminished or entirely absent brain activity in the orbital cortex region while the amygdala showed normal and sometimes heightened activity. This imbalance, and the inability of the two brain regions to effectively counteract each other, may help explain how threatening situations can become explosive in some people.
Neuroscientist James Fallon of the University of California, Irvine, elaborates on this same concept, saying, “When there’s an imbalance of brain activity to which the orbital cortex isn’t doing its job, the area of the brain that drives your impulsive behaviors will take over. People with low activity in the orbital frontal cortex are either freewheeling types or sociopaths.” Additionally, brain injury to the frontal region of the brain in an otherwise healthy person can also lead to similar violent results.
Fallon has spent over 20 years of his career studying the brains of psychopaths, trying to decipher what makes their brains different from ours. Fallon observed findings parallel to those of Davidson. But along the way, Fallon ran into his own personal findings: that he comes from a lineage of violent ancestors — eight alleged murderers, in fact. What’s more, he scanned his own brain and found that he had the underpinnings of a murderer. Yet, to this day, Fallon has yet to commit a violent crime, or, for that matter, any sort of violence.
Just as we know that the brain of a killer reflects abnormalities, genetic makeup has also raised curiosity. If genes determine everything from our eye color and hair color to our height and body structure, could they also define our behavioral fate?
In recent years, scientists have been able to pin down the genetic makeup — one gene, in particular — that predisposes certain people to aggression and impulsive violent behavior. The gene is the monoamine oxidase A, or MAO-A. Individuals with a certain variation of the MAO-A gene, which has earned the name “warrior gene,” have been shown to display higher levels of aggression in response to provocation, according to recent research published in the Proceedings of the National Academy of Sciences.
To confirm this, researchers conducted an experiment in which subjects played a computer game that offered the option to seek revenge by causing simulated physical pain on an opponent they believed had taken money from them. Researchers also tested the genetic makeup of each participant. The results of the study showed that MAO-A carriers were more likely than noncarriers to respond with “behavioral aggression” toward someone they thought had cheated them out of the hypothetical money.
Why such an effect because of one gene? The warrior gene is an enzyme that breaks down and regulates important mood-altering neurotransmitters in the brain, including dopamine, norepinephrine, and serotonin. We have various forms of the gene, which yield different levels of activity. Approximately one in three people carry the low-activity variation, which is associated with higher levels of aggression. Many researchers suggest that with the low-activity variation of MAO-A, the brain doesn’t respond to the calming effects of serotonin as it normally would.
