By now you've probably heard the summary: At the Stanford University laboratory of a psychologist named Walter Mischel, preschool-age children were left alone in a room after having been told they could get a small treat (a marshmallow or pretzel) by ringing a bell at any time to summon the experimenter. But if they held out until he returned on his own, they could have a bigger treat (two marshmallows or pretzels). The outcome, as it's usually represented, is that the children who were able to wait for an extra treat scored better on measures of cognitive and social skills many years later and had higher SAT scores. Thus, if we teach kids to put off the payoff as long as possible, they'll be more successful.
But that simplistic conclusion misrepresents, in several ways, what the research actually found.
1. What mostly interested Mischel wasn't whether children could wait for a bigger treat—which, by the way, most of them could. It wasn't even whether those who waited fared better in life than those who didn't. Rather, the central question was how children go about trying to wait and which strategies help. It turned out that kids waited longer when they were distracted by a toy. What worked best wasn't (in Mischel's words) "self-denial and grim determination," but doing something enjoyable while waiting so that self-control wasn't needed at all.
If you, like me, got the standard line, go read the rest of the article. Or if you can get by the paywall, read the journal article.