A marshmallow experiment was a psychology experiment done by someone at Stanford. Each child was given a marshmallow and told by the experimenter that they could eat it before fifteen minutes was up and that's that, or they could wait until the experimenter came back and get a second marshmallow. You could try it with your kids when they are old enough to understand you. The kids were followed in to adulthood, and it was found that the ones who got the second marshmallow had higher SAT scores and generally higher success in life.