Fifty years have passed since the Stanford marshmallow experiment, perhaps the most famous of all psychological tests. Small children were offered a choice between one marshmallow now or two if they could hold off for 15 minutes. (Different times were used over the course of the experiment.)
The willingness to wait turned out to be an extraordinarily good predictor of these children’s life outcomes. The ones with the greatest self-control were the most likely to go to college and get good jobs and the least likely to end up obese or in prison. There is even some suggestion that researchers, by merely carrying out this test, actually improved its subjects’ prospects in later life.