The Gullibility Tester

Once there was a man named Kevin. All of his friends said he was way too gullible. One day, at an arcade, he saw a new machine that said "Gullibility Tester" on the side. It had no screen, only some lights on the top. John decided to see how gullible he really was. He inserted a dollar. Nothing happened. Kevin wondered why nothing happened for a minute and then inserted another dollar.