I was talking with another member who hypothesized that maybe willpower is related to the "training" a person receives as a baby or toddler (feeding schedules and such) and that those who are put on a schedule are more prone to have greater willpower because they've been taught to wait from an early age. I think it's probably the opposite... that people who had less rigid parents in terms of feeding schedules and such learned that their needs will be fulfilled- that it shapes their view of fairness, so they're more willing to wait for things. Do you have any real-life experiences that might suggest willpower is related to "training" as a small child/ baby?
"[Contemporary US] parenting worries focus on relatively small variations in what parents do -- co-sleeping, or crying it out, playing iwth one kind of toy rather than another, more homework or les. There is very little evidence any of this makes much difference to the way children turn out in the long run. Nor does there seem to be any magic formula for making one well-loved and financially supported child any smarter or happier or more successful as an adult than another."
Gopnik largely focuses on how babies learn, not necessarily how they adapt to their environments. Ergo, baby training and a million other things may not make a difference in a child's cognitive abilities. She also takes the stance that humans are created to be diverse as part of our evolutionary makeup- that diversity is essential for the survival of the species. So, her take is mostly that kids need active adults in their lives and that variations in cognitive ability can generally be blamed on genetics. The majority of her work argues against the concept that cry-it-out methods cause brain damage. (That's the shortened version of it, anyway.) So, I don't think her opinion is relevant as it relates to willpower and/or resilience. Brilliant people can have no willpower at all and vice versa. I see no correlation there at all. You've taken her quote out of context.
There are loads of studies that look into early stresses. (I think it's fair to say that a baby left to cry alone is undeniably stressed.) Some bodies of research says this is a form of inoculation against later stresses. That, if mild enough, teaches babies how to self-regulate later. Here's one of those studies: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4736400/
There is also a ton of research that suggests early stress hampers cognitive abilities and results in the genes that help us manage stresses remaining shut off. There's about 100 links in this article: https://www.psychologytoday.com/blog/moral-landscapes/201112/dangers-crying-it-out
Of course there are a lot of factors that influence a person's abilities. Genetics, epigenetics, environment, etc... Does that mean we shouldn't bother trying to isolate triggers and behaviors to see which ones correlate? When you have enough data, a bigger picture begins to emerge that helps identify which things are actually related. We can't get this kind of data here on the Mug, but there's no harm in pondering the what-ifs.