Mental-health professionals have usually treated psychopathic behavior as a disorder—a large proportion of the prison population, after all, has been diagnosed with some version of the trait. But viewed from an evolutionary angle, psychopathy looks more like a feature than a bug. Most people are cooperative, trusting and generous. This pays off in the long term. It also creates an opening for those who would rather prey on society than join it.
A psychopath’s deceitful, manipulative, and callous nature equips him (it’s several times more likely to be a “him”) to fill this niche. Psychopaths’ deficit is in empathy, not reason. They understand morality, but they are immune to other people’s emotions. There aren't many openings for psychopaths, because if there were lots of them, there would be no society to plunder. Evolutionary biologists call this frequency dependence: it means that the rarer a trait becomes, the more it pays off. This advantage when rare makes the trait more common, which reduces its advantage. The effect is to keep multiple traits in balance. Sex is one example of frequency dependence: if males were more common than females, they would be less likely to find a mate, so it would pay to have female offspring, pushing the sex ratio back toward equality. Similarly, mathematical models suggest that if antisocial behavior is rare enough, it can prosper.
The benefit of psychopathy is that you exploit the altruistic without the cost of reciprocating. The downside is that you can cheat a person only so many times. Your victims will also warn their friends about you, and they may seek revenge. So a psychopath must stay one step ahead of his reputation.
Signs of the psychopath
Psychopaths’ psychology reflects this. They are often drifters. They have a dread of commitment in work, friendship, or romance. They go for the quick buck and the one-night stand. They are impulsive and uninhibited, and bore easily. A psychopath is someone who lives fast and does what he can to escape the consequences.
A few of us are psychopaths, and a few of us are saints who would never do a bad thing. Most of us are somewhere in the middle. We are predisposed to cooperate, but, unconsciously or not, we also weigh up the benefits of cheating against the likelihood and consequences of getting caught. Concern for our reputations is one thing that nudges us toward the saintly end of the spectrum.
Yet not every environment triggers the same concern. In a small village or a hunter-gatherer group, everyone knows everyone else’s business. There’s slim chance of getting away with anything. It’s easy to resist temptation in such an environment, and antisocial behavior is relatively rare in such communities. Urban life, on the other hand, is much more conducive to cheating. It’s no mystery what conditions make reputation powerful and encourage good behavior: transparency, accountability, and interdependence. Secrecy, impunity, and isolation do the reverse, making antisocial behavior more profitable.