But as she observed the children week after week, she began to question the task as a marker of innate ability alone. "If you are used to getting things taken away from you, not waiting is the rational choice. Then it occurred to me that the marshmallow task might be correlated with something else that the child already knows—like having a stable environment."This is a massive finding for two reasons. One, it gets at the issue of trust and how important it is t be able to trust your fellows in order for society to function. In a low trust environment, there is a serious risk of perverse incentives (and it is easy to forget this). This may be especially true of issues like employment contracts -- if you can't trust employers to keep their part of the implicit social contract then it is hard to defer gratification.
Two, all of this talk of impulse control leading to poverty is deeply misguided. Framing it as impulse control makes it seem like a feature of the person and not the environment. But it appears that it is also deeply related to how much you trust the systems in place. So perhaps the issue is growing up in unstable environments or in how much we can depend on people to be reliable.
That makes the whole issue seem both a lot clearer and a lot more complex.