You dipped your hand into ice-cold water and felt a sharp, freezing pain. Then the pain eased slowly. Later, you remembered how painful it felt at its worst and how it ended. The actual time your hand was in the water hardly matters. Or you watched two movie clips. One was short but had a scary jump scare at the end, and the other was longer with a scary peak in the middle but ended gently. Later, ... about the same scary-even though one was much longer. What's going on in your brain that makes this happen, and how can you prevent it? Take the quiz to find out what's really going on here.