Can a child pass up a tasty marshmallow? A researcher who wanted to know set up an experiment. He left a succession of four-year-olds alone in a room, seated at a table. On the table was a single marshmallow. The researcher told the children that they could eat the marshmallow when he left the room, or they could wait until he returned. If they waited, they would receive a second marshmallow. The children had a choice: one marshmallow now or two marshmallows if they were patient. The researcher then left the room. As you would guess, the researcher watched and recorded the responses of the children through a hidden window. You can probably guess the results. Some of the children snarfed down the marshmallow as soon as the door shut. Some squirmed and fidgeted for a while, but, in the end, …