That is the new forthcoming book by Jay Belsky, Avshalom Caspi, Terrie E. Moffitt, and Richie Poulton, which will prove one of the best and most important works of the last few years. Imagine following one thousand or so Dunedin New Zealanders for decades of their lives, up through age 38, and recording extensive data, and then doing the same for one thousand or so British twins through age 20, and 1500 American children, in fifteen different locales, up through age 15. Just imagine what you would learn!
You merely have to buy this book. In the meantime, let me give you just a few of the results.
The traits of being “undercontrolled” or “inhibited,” as a toddler are the traits most likely to persist up through age eighteen. The undercontrolled tend to end up as danger-seeking or impulsive. Those same individuals were most likely to have gambling disorders at age 32. Girls with an undercontrolled temperament, however, ran into much less later danger than did the boys, including for gambling.
“Social and economic wealth accumulated by the fourth decade of life also proved to be related to childhood self-control.” And yes that is with controls, including for childhood social class.
Being formally diagnosed with ADHD in childhood was statistically unrelated to being so diagnosed later in adult life. It did, however, predict elevated levels of “hyperactivity, inattentiveness, and impulsivity” later in adulthoood. I suspect that all reflects more poorly on the diagnoses than on the concept. By the way, decades later three-quarters of parents did not even remember their children receiving ADHD diagnoses, or exhibiting symptoms of ADHD (!).
Parenting styles are intergenerationally transmitted for mothers but not for fathers.
For one case the authors were able to measure for DNA and still they found that parenting styles affected the development of the children (p.104).
As for the effects of day care, it seems what matters for the mother-child relationship is the quantity of time spent by the mother taking care of the child, not the quality (p.166). For the intellectual development of the child, however, quality time matters not the quantity. By age four and a half, however, the children who spent more time in day care were more disobedient and aggressive. At least on average, those problems persist through the teen years. The good news is that quality of family environment growing up still matters more than day care.
But yet there is so much more! I have only scratched the surface of this fascinating book. I will not here betray the results on the effects of neighborhoods on children, for instance, among numerous other topics and questions. Or how about bullying? Early and persistent marijuana use? (Uh-oh) And what do we know about polygenic scores and career success? What can we learn about epigenetics by considering differential victimization of twins? What in youth predicts later telomere erosion?
I would describe the writing style as “clear and factual, but not entertaining.”
You can pre-order it here, one of the books of the year and maybe more, recommended of course.