Couldn’t some of the effect be attributed to the fact that the prisoners are not going to trust anyone coming in and presenting this situation. They would be completely justified to think something is up and not to trust the test presenters. It becomes a tangled mess with no scientific usefulness. College students on the other hand, are typically sheltered and gullible and would think it totally cool to play at being prisoners and betray each other just for the hell of it because it is all a laugh anyway.
Conclusion: life is more serious for victims of life’s injustices. Who woulda thunk it.