An eight-month psychological experiment revealed that people who are “nice” and conscientious are more likely to engage in cruel behaviour on the orders of an authority figure; the more nasty types are more likely to stand up for themselves and others. (Link.)
The theory is that people who are slightly contrarian are more likely to defy authority, while “nice” people are more concerned about people-pleasing – or at least pleasing the person whose wrath they are most likely to incur. (I wouldn’t call it “people pleasing” to administer electric shocks to other human beings.) Sometimes, we simply do not have the option of being kind to everyone around us, particularly when one person is trying to hurt another person. Our choice is about who we will offend or hurt, not whether or not we can escape it.