More interesting, and far less studied, are those who do not cooperate. In every experiment that I know of, including those fifth graders, a small percentage refuse to treat others as the person in charge suggests or orders. Yet those people could tell us something very important about fostering the same resistance to evil--a resistance that most of us would like to see in those around us. A resistance that could have prevented, for instance, the abuses at Abu Ghraib, and that could prevent abuses by prison guards, date rape, and other abuses of power that are widespread in our society (and others.)
All social species have some hierarchal organization, and all show some forms of at least seasonal dominance. Dominance behaviors are limited by survival needs...as animal studies have shown, the most aggressive and dominant individuals in the species eventually lower reproductive success in their own group. Similarly, the most aggressive human societies eventually tick off their neighbors enough to get wiped out or at least reduced in size. Limited dominance behavior improves survival (among other things, there's less internal disruption, less waste of energy within a herd or pack, if everyone understands where he/she fits in the group.) The "best" leaders (in terms of long-term fitness of the group) can switch off their aggression, switch off their dominance behaviors, and save that energy for other pursuits.
But what makes the independents? What makes a child, treated unfairly by another child, refuse to do the same thing to someone else? What makes a child refuse to participate in bullying? What combination of genes and experience creates the ability to say to oneself "This isn't fair, and I will never do this to someone else"...or "This isn't right and I won't do it no matter what"??
We don't know. Experiment after experiment studies the ones who do bully, who do administer painful shocks, who do carry their dominance behaviors as far as they can in that circumstance...and by all odds, these are ordinary people. They've been studied to see what their backgrounds are, how they're different from "everybody"--and they're not.
But the independents...those don't get studied.