An amusement park is like no other patch of land on earth. Full of bright colors, tantalizing games, infinite ice cream, and amazing thrill rides that give you the power to speed or fly, they open every year to teeming crowds on a quest for fun. The scene can feel anarchic--but there’s another way to think about it. The people who designed the rides, set up the games, and decided where to put the churro stands didn’t do it at random. The modern amusement park is, beneath the flash and the chaos, a carefully tuned psychological machine—a creation honed for more than a century to perfectly deliver a huge range of cognitive and physiological delights, pushing buttons you didn’t even know you had.