The Neuroscience of the Seven Deadly Sins

Techniques such as functional magnetic resonance imaging (fMRI), which highlights metabolically active areas of the brain, now allow us to view the biology of bad intentions.

The most enjoyable sins engage the brain’s reward circuitry, including evolutionarily ancient regions such as the nucleus accumbens and hypothalamus; located deep in the brain, they provide us such fundamental feelings as pain, pleasure, reward, and punishment.

The brain's conflict detector, located in the front, is activated by wrath and envy.

The medial prefrontal cortex, behind the forehead, plays a part in shaping self-awareness and responds to social sins like pride and lust.

Temptation and restraint go hand in hand. Our brains use cognitive control mechanisms to suppress naughty desires, making them less appealing.

• Cognitive control networks in the front of our brain help us resist
• They dampen the power of alluring impulses
• Restraint is a critical component in understanding temptation
• Neuroscience sheds light on this vital process

Research shows that the caudate, responsible for coordination, suppresses physical impulses. Whether it's lust, envy, or aggression, our brain's reward system battles against regions that keep us in line.

• If you feel tempted to do something, remember that your brain is fighting against itself.
• It's normal to feel the desire to act, but our brain regions work to prevent us from doing something we might regret.

It might be too strong to claim that evolution has wired us for sin, but excessive indulgence in lust or greed could certainly put you ahead of your competitors.

The brain doesn't have a single center of evil that medication or electrodes can fix. But with imaging technology, we can understand our bad habits better.

In the annals of sin, weaknesses of the flesh—lust, gluttony, sloth—are considered second-tier offenses, less odious than the “spiritual” sins of envy and pride.

That’s good news, since these yearnings are notoriously difficult to suppress.

Watching pornography calls upon brain regions associated with reward, sensory interpretation, and visual processing. It enlists the amygdala and the hypothalamus, which deal with emotional information; it also stimulates the reward processing ventral striatum, probably due to the satisfying nature of watching erotic stimuli. All said, the most notable thing about lust is that it sets nearly the whole brain buzzing.

Recent experiments have shown that brain scans can detect what arouses a man just by looking at the responses that occur. According to researcher Safron, fMRI scans reveal the intensity of arousal between different stimuli.

• Although women show a less intense response than men, it's still unclear why this is the case.

Research suggests our brain has a self-regulatory system to combat powerful urges.

Key points:

• Neural processing can be regulated via the right superior frontal gyrus and right anterior cingulate gyrus.
• This system allows us to control our impulses, unlike any other creature.

For centuries, overeating has been considered a sinful act. However, with advancements in science, it is now understood that physiology plays a powerful role in appetite. Physician Gene-Jack Wang has spent over two decades studying the brains of overeaters, and his research with colleague Nora Volkow has revealed that obesity and drug addiction affect the same brain circuits.

These pathways, which rely on the neurotransmitter dopamine, are often referred to as the reward system, but they are also involved in motivation, attention, decision making, and other complex functions. In their studies, Wang and Volkow found that both drug addicts and obese people are less sensitive to dopamine’s rewarding effects. Being relatively numb to the pleasure and motivation signal may make them more likely to chase after a stronger thrill: more food or a bump of cocaine. Excessive stimulation further desensitizes dopaminergic neurons, and the compulsion snowballs.

Mere laziness seems out of place among the deadly sins. It helps to know that this moral failing was originally conceived of as acedia, a term that suggested alienation and tedium, tinged with self-contempt. Acedia afflicted jaded monks who had grown weary of the cloistered life. Their sin was turning away from their moral obligations and toward selfish pursuits—a monastic form of ennui.

Sadness and listlessness are also hallmarks of major depression. With frontotemporal dementia the symptoms are caused by dead and dying cells; in depression the root cause is still unknown. In both conditions, the dorsolateral prefrontal cortex has an unusual pattern of activation.

Early theologians saw pride as the fundamental sin—the “queen of them all,” according to Pope Gregory the Great, who codified the list of seven deadly sins in the sixth century. Indeed, psychologists say that arrogance is second nature in Western society. Most of us perceive ourselves as slightly smarter, funnier, more talented, and better-looking than average.

These rose-colored glasses are important to mental health, functioning as a psychological immune system that protects us from despair. “Those who see themselves as they truly are—not so funny, a bad driver, overweight—have a greater chance of being diagnosed with clinical depression,” says Julian Paul Keenan.

Despite the enormous pool of potential research subjects, greed has not yet been systematically investigated in brain research. However, neuroscience does offer insight into a related phenomenon, the indignant outrage of the cheated.

The sin of pride turned on its head, envy is the most social of the moral failures, sparked by the excruciating awareness of someone else’s supreme talent, stunning looks, or extremely expensive car. For that reason, it is also the least fun of the deadly sins; feeling jealous provides no dirty thrill.

It may not have been the original sin, but rage is certainly primordial: Much of the brain circuitry active during anger is very basic and very fast. In humans, anger also enlists the conflict-detecting dorsal anterior cingulate cortex, which immediately alerts other regions of the brain to pay attention. The more upset you get, the more it activates, according to Tom Denson, a psychologist at the University of New South Wales in Australia. In people with short fuses, this part of the brain seems to be primed to feel provocation and personal slights, Denson says.

Some of us are more easily enraged than others, but few are able to stifle rage completely. Instead we may convert overt hostility into angry brooding.

To investigate the difference between short fusers and brooders, Denson antagonized his volunteers, insulting them while he scanned their brains. “Within seconds you see differences,” he says.

The medial prefrontal cortex, associated with self-awareness and emotional regulation, quickly lit up in angry brooders. So did the hippocampus, involved in memory. As they fume, people repeatedly relive the insult in their minds. Denson found that the degree of hippocampal activation predicted how much people tended to ruminate.

Probing the underpinnings of vengeful behavior, a German group led by neuropsychologist Ulrike Krämer allowed people who had been provoked during an experiment to punish their antagonist with a blast of extremely annoying noise. While the subjects pondered how loud to set the volume, the dorsal striatum, part of the brain’s reward circuitry, lit up at the prospect of retaliation.

“We have this primitive brain that says, ‘Do it! Do it!’” Denson says. Similarly, people asked to imagine themselves engaging in aggressive behavior actively suppress activity in the prefrontal cortex, where social information is processed. By deliberately inhibiting our natural social response, we ready ourselves to strike out.

Jordan Grafman recently found that virtue literally is its own reward. Altruistic behavior sends reward-related brain systems into a pleasurable tizzy—even more so than the prospect of self-interested gain. “The big punch line is that all things being equal, your reward system fires off a lot more when you’re giving than when you’re taking,” says Grafman, who is chief of the cognitive neuroscience section at the National Institute of Neurological Disorders and Stroke.

Call it the dirty little secret about being good: It might be even more fun than being wicked.