Popularly known as the marshmallow experiment, it was first conducted here some 40 years ago. Pre-schoolers were offered a choice between getting one treat (a marshmallow, originally) now, or two more if they waited for 15 minutes. The researchers wanted to see if you could teach children to rein in their impulses. It turns out you can. But then they tracked the kids through school, university and beyond. They found that children who were better able to delay gratification at age four did much better in later life.