The original trolly problem showed that people find it less repressible to kill people when no action is taken. It's presented both ways. "Pull the lever and kill five to save one" and "pull the lever to kill one and save five". You'd think that people would answer to kill one person in both cases, but it turns out people are biased against taking action (pulling the lever) regardless of how you word it, and so when it's worded as kill five if you do nothing, a lot of people will do nothing.