'It was jaw-dropping': The shocking lessons from an infamous experiment in obedience

Modern-day replications of one of history's most disturbing social psychology experiments, the Milgram study, reveal what makes ordinary people obey an immoral order – and how to resist.

In June 1961, a newspaper advert appeared in the Connecticut newspaper the New Haven Register, recruiting people for an innocent-sounding experiment at Yale University: "We will pay you $4.00 for one hour of your time. Persons needed for a study of memory."

Factory workers, barbers, businessmen and a wide range of other professionals were all wanted, the flyer said. No special education or experience needed. Those interested should mail their details to Stanley Milgram, a professor at Yale's Department of Psychology.

Forty men ended up joining the initial trial run of the experiment. They entered a lab, and under the guise of a word-learning task, were asked to deliver electric shocks to a stranger – up to a potentially lethal level. A majority of the men – 26 out of 40, or 65% – ended up delivering the maximum, lethal shock. In follow-up studies with other volunteers, a majority delivered the maximum shock even if the victim was presented as having a heart condition, or if he could be heard begging to be released.

The men had no idea that the shocks were actually fake, and the entire study was rigged. It was not about memory at all. Instead, it was a study of obedience, and cruelty – and it would become one of the most famous examples of ordinary people doing unthinkably brutal things when ordered to do so in a laboratory setting. 

Since then, researchers have used modified, milder versions of the Milgram experiment to study one of the most disturbing aspects of human nature: how, why and when we obey an immoral order. Their findings, along with details from Milgram's original experiments, not only shed light on some of humanity's worst impulses – but also give surprising insights into what can help us resist.

'We were just gasping'

It's hard to imagine an ordinary person inflicting extreme harm on a fellow human being. Most people are convinced they themselves would not do so, and that they would resist in a Milgram-type experiment. Even psychologists who research this behaviour can still find it startling when it happens before their eyes.

"It was kind of jaw-dropping to see these people, who seemed like perfectly normal, happy, wonderful individuals, press those levers and not object," says Jerry Burger, professor emeritus in social psychology at Santa Clara University in California.

In 2009, Burger ran a modified version of Milgram's study, stopping the volunteer at a lower (fake) shock. He had expected his results to be roughly the same as Milgram's. But watching the participants on a monitor, he and his team were still taken aback. "At first we were just gasping: I can't believe this person is doing this!" he says.

In Burger's 2009 study, 70% of participants obeyed to the end of the experiment. Unlike Milgram, Burger tested both men and women and found no major difference.

"We like to think of ourselves as independent, moral people who would resist an order if it conflicted with our values," says Tomasz Grzyb, a professor in social psychology at SWPS University in Poland, who ran a partial replication study in 2015. "But the evidence suggests that we should be much less certain of that. Under sufficient pressure, in the right social situation, people can find themselves doing things they do not actually want to do."

In Grzyb's replication study, which also involved lower maximum shock levels than Milgram's study, 90% of the participants obeyed to the end. There was no significant difference between men and women.

After the experiment, a psychologist talked to the volunteers about their experience to ensure they were OK. One young woman "began to cry very intensely", Grzyb says. "Through her tears, she said something like: 'This is just the kind of person I am. I do what people tell me to do. And only now, after taking part in this experiment, have I realised it. This is why things in my life happen the way they do.'"

What explains such obedience, even when it conflicts with our inner values?

'Disobeying uses more brain resources'

Emilie Caspar, a professor in experimental psychology at Ghent University in Belgium, studies how obedience influences human brain activity. In her studies, volunteers give real, mild electric shocks to another volunteer.

Caspar and her team use brain imaging methods, such as functional magnetic resonance imaging (fMRI), to observe what happens in the volunteer's brain when they deliver a shock under........

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