'One theory is that people learn things better when they get punished...'
Chilling words, but there's worse to come. Faced with a situation where you're told to inflict pain of increasing intensity on another person, most of us think we'd do the decent thing and decline. But Milgram's classic 1961 experiment showed that a shocking 65% of people keep on doing as they're told, in spite of warnings, screams and - most ominously of all - an eerie silence. Maybe people were more obedient back then? The 'just obeying orders' atrocities of the last war were, after all, still fresh in the memory (and were the inspiration, in part, for Stanley Milgram's study).
But no. The BBC repeated the experiment just last year and found that - of the twelve participants - only three were prepared to stop.
Here's a clip from the original experiment; if you can't be bothered with the preamble, fast-forward to about ten minutes to see the experiment in action. And as you watch, ask yourself this: how far would you go? And how could you be sure?