The thrill of the hunt, maybe, the same instinct that keeps us alive and makes us run and hide from prey. Hide-and-seek. The fear of being found, the excitement of the seeker tormenting the, um, encouraging them to get out. Isn't that just sadistic? They won't, of course, but hearing that voice makes their hearts beat fast, makes them hold their breath, curl up to hide better... the point is to scare them, torment and intimidate them into exposing themselves in fear.

[Darkly:] That's just kids being kids.

We know what it's like to be scared, but when the roles are reversed, we enjoy wielding fear over someone else. Isn't that messed up?

Who knows, maybe it is human nature.