so what? Did they get a grade on their participation? I'd bet not. So why would they care what the hypothesis was?
>> The experimenters intervened directly in the experiment, either to give precise instructions, to recall the purposes of the experiment, or to set a general direction.
PZ says they said, "We noticed this morning that you weren't really, you know, lending a hand, and I was wondering if there's anything's wrong… We really want to get you active and involved because the guards have to know that every guard is going to be what we call a “tough guard”… what I mean by tough is [that] you have to be firm, and you have to be in the action… It’s really important… for the workings of the experiment [because] whether or not we can make this thing seem like a prison—which is the aim of the thing—depends largely on the guards’ behavior."
Sorry, but I don't see how this invalidates anything. If some of the guards were just phoning it in and not taking it seriously, they did need a talking-to.