Milgram's experiment (look up in Wikipedia) is a rather old very well known unethical experiemt where establishing the idea of strong aversive conditioning among human participants took place but fear of authoritarian person were even stronger. Electric shocks were used on a not concrete level. Stanford experiment is an other experiment displaying the black side of the human being. Cruelty towards fellow mates is something that has existed since the human was created. Snakes are still strong aversive US.