Inside an Evil, Dangerous Brain

Who knows what evil lurks in the brains of men? Increasingly, the neuroscientists do. Over the last few decades, they’ve made headway in discovering what makes violent criminal minds tick. No scientist claims complete comprehension. In fact, they like to say that if the human brain were simple enough to understand, we’d all be too simple to understand it. Yet their research has shown that bad-guy brains do tend to have a loose biochemical screw.

The average adult brain is 3 pounds (1,400 grams) of unrivaled processing power, with 500 trillion synaptic connections organized into various “maps” governing language, movement, vision, hearing, and more. Chemicals called neurotransmitters infuse the whole works and carry messages from one brain cell to another. Two of these neurotransmitters – serotonin and noradrenaline – tend to go wrong in violent people.

Serotonin: “Don’t Worry, Be Happy”

Serotonin is the brain’s “don’t worry, be happy” juice. It’s the body’s own Prozac. (In fact, Prozac works by helping the brain make use of its serotonin.) At normal levels, serotonin lets the “reasonable” part of your brain maintain control over all sorts of primitive, but pretty useful, drives – like sex, hunger, fear, and aggression.

Of course, serotonin doesn’t prevent you from acting on these drives. It just puts the brakes on, giving the reasonable part of your brain enough time to say “back in the cage, monkey boy” or “go for it.” Not enough serotonin, and your brain lacks brakes. Drives and emotions rule. Too much, and you’re an obsessive-compulsive wreck, agonizing over decisions and details.

Noradrenaline: “Danger! Danger, Will Robinson!”

If serotonin puts on the brakes, noradrenaline steps on the gas. It’s the loyal robot that waves its arms and screams, “Danger! Danger, Will Robinson!” When external events command immediate action, noradrenaline literally focuses the mind, preparing the brain for “fight or flight” decisions and triggering the production of adrenaline and other biochemical concoctions meant to give the body an edge.

Too much noradrenaline, and you’re a high-strung hothead stuck on DefCon-2, always ready for a fight. Not enough, and you’re one cool cucumber, a daredevil stuntman who needs to jump off bridges to get the rush most folks get saving money at Wal-Mart.

Crimes of Passion vs. Cold-Blooded Evil

Scientists now know that violent brains tend to have the wrong amount of serotonin and noradrenaline. Low serotonin sets the stage. Without a full set of biochemical brake pads, you’re likely to have trouble controlling emotions and drives, including aggression. In fact, when researchers temporarily lowered the amount of serotonin bathing the brains of volunteers at McGill University in Montreal, those volunteers proved far more willing to sting people with electric shocks.

High noradrenaline makes matters even worse. Imagine a brain that lacks emotional brakes and won’t drive 55, and you may be imagining an impulsive, violent criminal. Cold-blooded killers seem to represent a special case – a case not of too much noradrenaline but of too little. Studies of convicted murderers in California suggest that serial killers and other remorseless, premeditating sociopaths suffer not from a surfeit of emotions but from a lack of them. Understimulated by life, they tend to kill, literally, for the thrill.

Nature vs. Nurture

Scientists are quick to point out that none of these biochemical conditions is deterministic. People with low serotonin might find it harder to control their impulses, but that doesn’t mean they can’t. Nor is everyone with low serotonin and high noradrenaline destined for prison. It takes far more than bad genes to make bad guys. In fact, neuroscientists say that when it comes to the brain, nurture is as important as nature.

Human beings don’t contain anywhere near enough genes to build a working brain. It’s just too complex. Your genes simply ensure that you get all the mental material you need to get started (and then some, actually). Your brain, interacting with the world around it, has to figure out for itself how to work. Remarkably, it does. Within seconds of a newborn detecting its mother’s scent for the first time, neural networks form to make sense of the experience. Such experiences constantly shape your brain.

The Great Thing about Good Lobes

Those moral lessons from Mom and Dad shaped your brain, too, like so much parental Play-Doh. Infusions of morality affect one part of the brain in particular, the area scientists call your prefrontal lobes (the frontalmost part of your frontal lobes). Just behind your forehead, your prefrontal lobes work hard to keep you from doing stupid things. If shaped and strengthened by good experiences, they add a bit of wisdom to your impulsive desires and help you fit in.

Good prefrontal lobes prioritize incoming information, consider all options, and come up with an endless stream of plan Bs. Those fleeting urges to do or say something you shouldn’t all end up here, where you weigh consequences and outcomes and, hopefully, choose to stay on the straight and narrow.