I'm not necessarily disagreeing with this conclusion, but I AM disagreeing with the experiement they used to come to this conclusion.
You see, several decades ago, they experiemented on children. They told the children that they could eat one marshmallow now, or they could wait and get two marshmallows later. They followed the kids over the next several years and discovered that the kids who were able to deny themselves the initial marshmallow in favor of gaining an extra marshmallow were more successful and less inclined to commit crimes, etc.
But here's why the experiment is stoopid. It makes two very big and incorrect assumptions.
1) That marshmallows are awesome - so awesome that no child would ever NOT want more marshmallows.
2) That all children come from awesome families where trusting adults is a good and reasonable thing to do.
Let's say a child comes from a family that is...less than perfect. Perhaps her parents are alcoholics. Perhaps they are emotionally abusive and manipulative. Perhaps she lives in complete and utter chaos.
Now tell that child that she can have the marshmallow in front of her now, or she can wait for two marshmallows later. Everything in that child's experience tells her that adults cannot be trusted. Sure, the guy in the lab coat SAYS there will be more marshmallows later, but that doesn't mean anything. What if the lab coated man gets high and nods off and forgets all about the marshmallows? What if his pimp comes in and smacks him around for a while and marshmallows become a low priority? What kind of moron child would wait for a marshmallow that might never come, when she could eat the one in front of her, now? CARPE DIEM!!!
And further, could we not assume that those children who took the initial marshmallow do more poorly in life because of their horrible home lives, rather than their "innate inability to delay gratification"?
Also, marshmallows are not that great. I mean, yes, they are relatively tasty, but in all honesty, I'd rather have one marshmallow than two. You only really need one, and that's plenty. And you certainly don't want to eat a marshmallow all on its own. You need to make smores or put the marshmallow in hot chocolate or similar. Maybe some of these kids simply didn't give a care about how many marshmallows they got because whatever. It's just a freaking marshmallow. It's not like it's hollandaise sauce or mashed potatoes or something wonderful. You know?
Anyway, I'm not saying self control and delaying gratification is bad. It's good. I'm just saying that this experiment is flawed, and it doesn't prove anything, except that the developers of psychological experiements all come from well-adjusted, wholesome homes and they have massive boners for marshmallows.