Diminutive American servicewoman Lynndie England, recently shown in photographs holding a leash attached to a naked Iraqi's neck in Baghdad's Abu Ghraib prison, has resurrected interest in a couple of classic psychological experiments. Both demonstrate how easily normal people can turn nasty.

First came Stanley Milgram, at Yale University, who, in a series of experiments, had volunteers administer what they thought were harmful electric shocks to strangers, ostensibly as punishment for getting the answer to a question wrong. Two-thirds inflicted 'danger' level shocks of 450 volts on victims screaming in apparent agony in an adjoining room when encouraged to do so by a man in a white laboratory coat. In fact, everyone bar the volunteers was in on the act. The volunteers later described how they had been taken in by the scenario and many were somewhat puzzled and disturbed by exactly why they had gone along with it.