Most of us would torture others if ordered to do so, a study has found.
Scientists revealed that 70 per cent of volunteers, when encouraged by authority figures, continued to administer electric shocks - or at least thought they were doing so - even after an actor claimed they were painful.
Researchers at Santa Clara University in California said the experiment can only partly explain the widely reported prisoner abuse at the U.S.-run Abu Ghraib prison in Iraq or events during World War II.
Jerry Burger said: 'What we found is validation of the same argument - if you put people into certain situations, they will act in surprising, and maybe often even disturbing, ways.
U.S. soldier Lynndie England holds a leash tied around the neck of a naked man in Abu Ghraib prison outside Baghdad. She was later sentenced to 36 months in jail for abusing prisoners
'This research is still relevant.'
Burger was copying an experiment published in 1961 by Yale University professor Stanley Milgram, in which volunteers were asked to deliver electric 'shocks' to other people if they answered certain questions incorrectly.
Milgram found that, after hearing an actor cry out in pain at 150 volts, 82.5 per cent of participants continued administering shocks, most to the maximum 450 volts.
The experiment surprised psychologists and no one has has tried to replicate it because of the distress suffered by many of the volunteers who believed they were shocking another person.
'When you hear the man scream and say, "let me out, I can't stand it," that is the point when the real stress that people criticised Milgram for kicked in,' Burger said.
'It was a very, very, very stressful experience for many of the participants. That is the reason no one can ethically replicate the experiment today.'
Burger modified the experiment, by stopping at the 150 volt point for the 29 men and 41 women in his experiment.
The results of the experiment can only partly explain the reported prisoner abuse at the U.S.-run Abu Ghraib prison in Iraq, said researchers
He measured how many of his volunteers began to deliver another shock when prompted by the experiment's leader - but instead of letting them do so, stopped them.
In Milgram's original experiment, 150 volts seemed to be the turning point.
In Burger's modified experiment, 70 per cent of the volunteers were willing to give shocks greater than 150 volts.
At one point, researchers brought in a volunteer who knew what was going on and refused to administer shocks beyond 150 volts. Despite the example, 63 percent of the participants continued administering shocks past 150 volts.
'That was surprising and disappointing,' Burger said.
Burger found no differences among his volunteers, aged 20 to 81, and carefully screened them to be average representatives of the U.S. public.
Burger said the experiment, published in the American Psychologist, can only partly explain the widely reported prisoner abuse at Abu Ghraib prison in Iraq or events during World War II.
American soldier Lynndie England was one of several U.S. personnel convicted in connection with torture and prisoner abuse at the Abu Ghraib prison.
England was found guilty of inflicting six counts of sexual, physical and psychological abuse on Iraqi prisoners.
She was photographed leading a prisoner by a leash and giving a thumbs up as naked men were forced to clamber on top of each other.
She was released in March 2007, after serving half of her 36-month sentence.
England later told a TV station that she had been ‘instructed by persons in higher ranks’ to commit the abuse.
Burger wrote: 'Although one must be cautious when making the leap from laboratory studies to complex social behaviors such as genocide, understanding the social psychological factors that contribute to people acting in unexpected and unsettling ways is important.
'It is not that there is something wrong with the people.