Interesting, but one small factor is not addressed by the "experiment."
They should have asked the kids if they even wanted a second one before they left them alone. When I was that age, I distinctly remember I never, ever wanted more than one marshmallow at a time.
Isn't it possible that at least some of them didn't care anything about the second one?
And, is it possible that some, if not all, that did not care about the second, may also have been successful later on?
These questions aren't addressed at all.
Not that the point isn't valid. I think it is. I just would be more interested had they gone into more depth with it. Success principles are not always as simplistic as so many make them out to be.
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I'm not likely to be around much longer. As before when I first signed up here years ago, I'm finding that after a long hiatus, and after only a few days back on here, I'm spending way too much time here again already. So I'm requesting my account be locked, banned or whatever. It's just time. Until then, well, I dunno...