People who flick the switch to evil under direction feel as though they aren't really responsible. 3drenderedlogos.com/Shutterstock

Light has been thrown on the reasons for one of psychology's most famous and shocking experiments, and on the awful behavior that inspired it. A new study goes some way to answering the question of why people who are normally decent will, under orders, inflict horrible violence.

In the 1960s, psychologist Stanley Milgram horrified the world by instructing volunteers to inflict increasingly powerful electric shocks on people who had failed memory tests. The experiment was an illusion – the shocks were not real and the “victims” were actually actors. Nevertheless, most of the study's participants appear not to have suspected this. They genuinely thought they were administering shocks that eventually became so powerful they might have killed the victim. Yet only a third refused orders, and even those went disturbingly far.

Five decades later, Professor Patrick Haggard of University College London has used new technology to provide insight into why people would do this.

"People often claim reduced responsibility because they were 'only obeying orders.' But are they just saying that to avoid punishment, or do orders really change the basic experience of responsibility?" Haggard said in a statement.

Haggard tested what is known as the “sense of agency,” or whether people feel that their actions have caused some external events. Past experiments have demonstrated our sense of agency can alter our perceptions of time. We are so used to the idea that flicking a switch turns on a light that when a small delay is inserted in the process our brains often fail to notice it. The sense of immediacy between action and result can be used to measure how responsible we feel.

In a previous study, Haggard made the observation that many people feel a greater sense of agency, as measured by time perception, over events with a positive outcome than a negative one. It is not just embarrassment, it seems, that explains why “Victory has a thousand fathers, but defeat is an orphan.” People really are more likely to think they were responsible for successes than failures.

This time Haggard had participants in his study deliver electric shocks – less severe than those Milgram simulated – or take money from the victims. Sometimes an experimenter ordered them to do this, on other occasions the choice was up to them. This time the shocks were definitely real – participants took turns administering and receiving. Disturbingly, when given the choice a majority chose to not only take the money, but shock their counterparts.

People's sense of time between action and reaction suggest they felt greater responsibility in the second scenario than the first. Caspar et al, Currrent Biology

In Current Biology Haggard reveals that participants who were pressured to administer shocks perceived a longer gap between button-pushing and shocks occurring, compared to those who chose to act through greed or sadism.

“People who obey orders may subjectively experience their actions as closer to passive movements than fully voluntary actions,” the paper noted.

In recent years the debate has been revived on interpreting Milgram's work. Haggard's findings add to this, and may feed into even more important questions – why some people resist unethical orders, and how others can learn to do the same.