Marshmallow Aka Will Power.

The granddaddy of willpower science is the “marshmallow experiment”. Devised by Walter Mischel in 1972, it’s a classic of social psychology and the bedrock for all later research on willpower and self-control. In it, researchers left four year olds alone in a room with a marshmallow and told them that if they could wait until the experimenter returned they’d get two.

You can watch a video of the experiment here (if you have the willpower). I really love the kid at 2.45.