If people are biologically equipped to care about others, why do they so commonly treat each other badly? If brains are set up for caring and empathy, why is the world full of child neglect and abuse, battered spouses, rape, murder, corruption, and war? Would it not be more plausible to suppose the people are inherently evil, so that good behavior is actually the rare accomplishment of cultural developments such as religion?

Religions have long worried about the problem of evil, of how there could be so much bad in a world created by a supposedly benign God. The Christian doctrine of original sin supposes that people are inherently evil and need to be redeemed by the church. Even without religious impetus, there is a major problem of explaining why people who are theoretically capable of good are so often prone to fall short of ethical standards.

This question is analogous to the question of how disease arises. Bodies function normally most of the time, but can easily malfunction given environmental problems such as viruses or just wearing out through age. Normal functioning depends on the operations of biological mechanisms, which are combinations of interconnected parts whose interactions cause regular changes.  Diseases are best understood as breakdowns in mechanisms, for example when the influenza virus disrupts the operations of cells and organs such as the lungs.   

Immoral behavior is not in itself a disease, although it sometimes results from diseases such as brain tumors. What are the breakdowns in mechanisms that lead people to behave in evil ways? Here, evil just means being severely immoral, acting strongly contrary to the needs of people.

Consider an intense form of evil, pedophilia, in which adults take sexual pleasure in children. Most people find children deserving of care, so how does it happen that approximately 1 percent of males are inclined to have sex with children? Pedophilia qualifies as evil because of the great harm caused to abused children, from immediate distress to long-term mental illness and difficulties with relationships, sometimes leading to suicide. The causes of pedophilia seem to be varied, including brain defects in frontotemporal regions, psychological problems with impulse control, and past history of being abused as a child. No comprehensive account is currently available, but, pedophilia will likely turn out to be the result of breakdowns in a combination of molecular, neural, psychological, and social mechanisms, interacting to produce evil acts.

More general breakdowns in moral behavior occur in psychopaths, who routinely engage in manipulative, self-serving behaviors with no regard for others. The causes of psychopathy are still up for discussion but are likely as disparate as other aspects of personality, deriving from combinations of genetics, epigenetics (chemical attachments to genes), early childhood learning, and learning from later environments. Simon Baron-Cohen describes psychopaths as having zero degrees of empathy because of neural deficits in brain areas such as the ventromedial prefrontal cortex, but he also discusses psychological causes such as inability to recognize fear, and social causes such as parental neglect. Molecular causes may operate through epigenetic effects such as the methylation of the gene for oxytocin receptors. Hence psychopathy also seems to be a case of emergence from breakdowns in interacting mechanisms.

Even non-psychopaths can do evil things because of neural, psychological, and environmental effects. Thinking can fail to produce good moral judgments when people forget about relevant values that ought to contribute to their processing of emotional coherence. Empathy deficits can result from stress, fatigue, or alcohol, contributing to the neglect of the needs of others. Men with high testosterone or low oxytocin may be more inclined to violent behavior. Environmental stresses such as lack of food, water, and sleep can lead to faulty emotional judgments through limited coherence calculations.

In addition, ordinary people are adept at giving self-serving justifications for why their actions are not immoral, a kind of motivated inference. Guilty feelings can be resisted by concocting stories about how situations are ambiguous, actions have complex consequences, and other people are worse. For example, corrupt politicians may be able to convince themselves that they really are doing their best.

Evil actions can also have social causes. Peoples’ mental states are intensely influenced by emotional communication from others, and groups can end up engaging in more risky behaviors than the individuals would normally do on their own. Authority figures giving orders can produce behaviors in people that they later consider inappropriate, as in the famous Milgram experiments where participants agreed to give intense electric shocks to learners.

Thus, even without specific problems such as pedophilia and psychopathy, evil behaviors can result from breakdowns in molecular mechanisms (alcohol), neural mechanisms (frontotemporal dementia), psychological mechanisms (poor impulse control), and social mechanisms (peer influence).

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References

Baron-Cohen, S. (2011). The science of evil:  On empathy and the origins of cruelty. New York: Basic Books.

Joyal, C. C., Beaulieu-Plante, J., & de Chantérac, A. (2014). The neuropsychology of sex offenders: a meta-analysis. Sexual Abuse, 26(2), 149-177.