from Maia Szalavitz:
…So, what determines which children will fall among the lucky 25% who can successfully resist the marshmallow? Is it an inherited genetic advantage that produces greater impulse control? Is delaying gratification a learned behavior? Or could children be making conscious choices about this specific task based on similar prior experiences — involving adults who promise better rewards later — of whether waiting really pays off?Researchers led by Celeste Kidd at the University of Rochester devised a clever way to find out.