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Are Humans Good or Evil?

Chemistry can provide the answer.

One hundred and fifty years in prison. Shame brought to his family for bankrupting so many friends. His son took his life. These are the costs Bernie Madoff incurred for running a decades-long Ponzi scheme that appropriated an estimated $18 billion from investors. If Madoff was just maximizing his income, then why did so many cheer when he did the "perp walk"?

On the other end of the spectrum is Agnes Gonxha Bojaxhiu, who at age 18 left her comfortable home to become a missionary, never to see her family again. Agnes, better known as Mother Teresa of Calcutta, devoted 45 years of her life to helping the impoverished. She received the Nobel Peace Prize in 1979 and after her death was beatified by the Roman Catholic Church, a critical step toward sainthood. In 2010, on the 100th anniversary of her birth, there was a worldwide celebration of her service to humanity. Why did people across the planet praise her selflessness?

Human beings are highly social creatures. Because of this, we are intensely interested in what others are doing, and why. We need to know who is good and bad and therefore who we want to avoid and who we can tolerate.

All of us recognize virtue and vice when we see it, with virtues generally being actions that benefit others and vices entailing selfish acts. The moral philosopher Adam Smith (also the "father" of economics) argued in his 1759 book The Theory of Moral Sentiments that virtue derives from our innately social nature in which we cannot help but share in the joy and pain of those around us. Smith argued that when we do things that cause others pain, we also feel pain.

Because our biology causes us to avoid pain, we typically avoid such actions. Similarly, we enjoy pleasure and vicariously experience pleasure when we do something that brings happiness to others. This "fellow-feeling," or what we would now call empathy, is what maintains us in the community of humans. This is a critical requirement for a social creature. Smith was the first to clearly make the case that it is our social nature that motivates human virtue and is the reason why we vilify vice.

For the last 10 years, my lab has put this Smithian idea to the test by searching for a neurochemical basis for virtue and vice. We have focused on the chemistry behind behaviors because people seldom offer clear explanations for why they are doing what they are doing. Motivations matter because they ascribe meaning to actions. So, we have people make decisions that are virtuous or selfish while measuring their brain activity.

This research has largely confirmed Smith's argument for why humans can be virtuous. We have shown that virtuous behaviors are caused by the brain's release of the neurotransmitter and hormone oxytocin. When oxytocin is high, costly caring and helping behaviors follow. When we inhibit oxytocin release (for example, in experiments where I've administered testosterone to volunteers), virtue wanes and selfishness dominates. Oxytocin release makes us feel empathy and by doing so increases our sensitivity to the feelings of those around us. I recently published an article reviewing these findings.

By finding the brain mechanisms driving virtue and vice, we have also added subtlety to Smith's views. For example, we have identified why variations in a women's menstrual cycle affect her trustworthiness, and why high social status males are less likely to be cooperative and more likely to violate sharing norms. We have also shown that context matters. We are a highly adaptive species and what is appropriate in Guadalajara may be inappropriate in Kansas City.

So are humans moral or immoral? The biological answer is that we have evolved behaviors that increase our chances of survival and reproduction. When in a stable and safe environment with enough food in our bellies, having a biology of morality sustains our place in the community of humans who help ensure our biological imperatives. In highly stressful, resource-poor environments, we'll step on whoever is in front of us if it helps us survive. The exceptions to this rule are the 5 percent of the population who I've found do not have an oxytocin response and are pathologically selfish like Madoff, and another few percent who are nearly pathologically virtuous like Mother Teresa. The rest of us vacillate between good and evil.

We're a complicated species—both moral and immoral as our environment and physiology dictate. But mostly the moral dominates. Not so bad for a complicated, big-brained mammal.

More from Paul J. Zak
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