An ethics professor at Princeton Seminary asked for volunteers for an extra assignment. Fifteen students showed up. He divided the group of fifteen into three groups of five each. He instructed the first group of five to proceed immediately across the campus to a certain spot; if they didn’t get there in fifteen minutes their grade would be affected.
A minute or two later he instructed the second group to proceed across the campus to the same spot; but they were given forty-five minutes to get there.
After they left he instructed the last group to go across the campus to that spot too; but they were given three hours for the trip.
Now, unknown to any of these students, the teacher had arranged with three students from the Drama Department to meet them along the way, acting as people in great need: the first one they met covered his head with his hands and moaned out loud as though in great pain; the second, a little bit further along the way, was on some steps lying face down as if unconscious; the third, on the very steps of the destination, acted out an epileptic seizure. You know what the ethics professor discovered? Not one of the first group stopped, only two of the second group stopped, but all five of the third group stopped.