As I understand this variation at each incorrect answer the victim was shocked only when the teacher forced his hand on a shock plate. At 150 volts, the learner refused to place his hand on the plate, and the experimenter ordered the subject to hold the victim's hand on the plate. Obedience wasn't measured in the number going to 450 as in the original, but the number who obeyed beyond 150. The results were 30%. I believe I recall reading this in Milgram's original 1974 book, it's been a while since I read that though!