11/20/2013 07:21 am ET Updated Jan 25, 2014

Do Good People Turn Evil?

Half a century ago, Holocaust perpetrator Adolph Eichmann was on trial. The prosecutor called him "a new kind of killer, the kind that exercises his bloody craft behind a desk." Reporting on the trial, Hannah Arendt drew a different conclusion. She argued that Eichmann was a plain bureaucrat, seeing himself as "a law-abiding citizen" who "did his duty" and "obeyed orders." She called it "the banality of evil."

The core claim was that if you put good people in a bad situation, bad things will happen. Soon, evidence emerged to support this chilling idea. At Yale, psychologist Stanley Milgram showed that ordinary men would inflict severe pain on others simply because they were asked to do so by an authority figure in an experiment. When a man failed to learn a set of words, a scientist in a white coat told them to deliver increasingly harmful electric shocks. Many went all the way to 450 volts -- even after the "victim" (an actor) complained of heart trouble. "It may be that we are puppets -- puppets controlled by the strings of society," Milgram lamented.

At Stanford, psychologist Philip Zimbardo randomly assigned students to play the roles of prisoners or prison guards. Cruelty ensued: the guards forced the prisoners to sleep on concrete and took away their clothes. "In only a few days, our guards became sadistic," Zimbardo writes: the "power of a host of situational variables can dominate an individual's will to resist."

These were two of the most powerful demonstrations in social science, by two brilliant thinkers, and they've been taught to a generation of students. But what if we've drawn the wrong conclusions from them?

Although many people do underestimate the power of situations in driving behavior, more recent evidence shows that individual differences matter far more than we thought.

Who Signs Up For a Prison Study?
In the prison demonstration, Zimbardo claimed that ordinary people underwent a transformation. In his book, he calls it The Lucifer Effect, proposing to explain "how good people turn evil." Yet the students who participated were recruited for "a psychological study of prison life." What kind of person volunteers for such a study?

When psychologists Thomas Carnahan and Sam McFarland compared people who signed up for a psychological study of prison life versus a general psychological study, the differences were stark. The people who volunteered for a prison study scored:
• 27% higher on aggression (tendency to attack or harm others)
• 10% higher on authoritarianism (expecting obedience from subordinates)
• 10% higher on Machiavellianism (willingness to manipulate others for personal gain)
• 12% higher on narcissism (seeing oneself as superior)
• 26% higher on social dominance (believing in the importance of hierarchy)
• 7% lower on empathy: (concern for others in need)
• 6% lower on altruism: (motivation to help others at a personal cost)

Psychologists have long described narcissism and Machiavellianism as two thirds of the dark triad of personality. The third is psychopathy (antisocial behavior and a lack of empathy and remorse), and now there's a fourth dark trait that parallels the behavior of the prison guards: sadism (the tendency to feel pleasure from inflicting pain).

When people with these types of dark traits signed up for a prison study and became prison guards, they were surrounded by others who shared their tendencies, and they expressed them. People "do not automatically assume roles given to them," conclude the psychologists Alexander Haslam and Stephen Reicher, after running their own prison experiment with cooperation from the BBC. Rather, "particular individuals with particular beliefs make tyranny possible."

Who's Willing to Deliver a Deadly Shock?
In Milgram's original research, only 65 percent of participants delivered the maximum voltage of electric shocks. The psychologist Thomas Blass, author of The Man Who Shocked the World, was curious about the differences between people who obeyed and those who objected. When Blass analyzed the 21 different variations of Milgram's experiment, he found that certain personality traits and beliefs predicted who continued delivering the shocks.

People were more likely to deliver painful shocks if they were authoritarian. The shockers were also significantly more trusting of others (they assumed the scientist would do the right thing) and used to following the lead of others (they believed life events were driven by external forces like luck, chance, or fate, rather than internal forces like effort and willpower).

Bad Barrels or Bad Apples?
Could it be that good people don't turn evil? Even at war, most people aren't willing to kill. As biologist Frans de Waal writes:

It is a curious fact that the majority of soldiers, although well armed, never kill. During World War II, only one out of every five U.S. soldiers actually fired at the enemy. The other four were plenty courageous, braving grave danger, landing on the beaches, rescuing comrades under fire, fetching ammunition for others, and so on, yet they failed to fire their weapons... Similarly, it has been calculated that during the Vietnam War, U.S. soldiers fired more than fifty thousand bullets for every enemy soldier killed. Most bullets must have been fired into the air.

This isn't poor accuracy; there's clear evidence for intentionality on the part of soldiers. As Dave Grossman writes in On Killing,

The weak link between the killing potential and the killing capability of these units was the soldier. The simple fact is that when faced with a living, breathing opponent instead of a target, a significant majority of the soldiers revert to a posturing mode in which they fire over their enemy's heads.

Most people aren't willing to inflict irrevocable harm on others. Consistent with this idea, historian David Cesarani has challenged Arendt's original conclusions that Eichmann was just a bureaucrat. Arendt only witnessed part of the trial, where Eichmann managed to put on a "deliberately banal façade," Cesarani writes in Becoming Eichmann. "Eichmann's Nazi convictions and his unquestioning obedience to orders were part of the same ideological package... Either Eichmann wanted to kill Jews or he didn't care if they perished... To the fully indoctrinated Eichmann, the Jews had no intrinsic claim to life."

Bad people are more likely to opt into bad situations. When they band together, all too often, evil is the result.


Adam is the author of Give and Take, a New York Times and Wall Street Journal bestseller on how helping others drives our success. Follow him on LinkedIn at and on Twitter @AdamMGrant