The marshmallow test was the brain child (heh,heh double pun intended) of the father of 4 young girls around the age of 4 years old. He realized that his 4 y.o. could be convinced to put gratification now for something later. He developed a test where young children were told that they could have the marshmallow on the table now or, if they waited until the researcher returned, they could have two marshmallows. The researcher never actually returned, the test was about how long gratification could be delayed. The results varied from mere seconds to over 10 minutes. The children were local so later when his daughter was 17, he asked how some of her friends were doing. Some were off to college and some were 'dropping out'.
Interested, the researcher found as many of the subjects as he could find and it seems that those children who able to resist temptation the longest were doing better. In fact there seemed to be a significant correlation between the length of time the child could resist and their SAT scores. They have been following the 'children' for 40 years now and the correlation still seems to hold between success and resisting temptation
The difference was in hundreds of points on their SATs!! And thousands of dollars of income.
The interpretation of the results are pretty varied
The videos of the tests are incredibly cute - 4 year old kids trying to resist temptation. Take a look.