ctim is still willing to "playthe game.
I think the fact that the participant does not hear any objection from the victim and that the victim still responds up to this point gives him the impression that the victim still thinks that the benefit of scientific gains from the experiment outweighs the risks/harms to which he is exposed. The participant might assume that the victim would speak up if he was uncomfortable. I would guess that the participants who did stop at this point would have stopped earlier if the victim had the same response then. Yet, this still does not explain why 65% of the participants continued to shock the victim until the end.