"Triumphs of Experience: The Men of the Harvard Grant Study," by George E. Vaillant.

This book summarizes 75 years of intensive tracking and study of over 200 men who were sophomores at Harvard, starting in 1938 through 1944. They were intensively examined physically and psychologically, and their lives and careers tracked into their eighties and nineties. The author is a pschyciatrist and professor, and is thrilled to have such a long-term body of research to apply scientific and statistical methods to. He shows that men can change and adapt throughout life, and aren't always trapped by environmental factors such as unfavorable childhoods, emotional shortcomings while young, etc.

His thumbnail bio's of these men were very interesting. Most were very successful in their fields compared with average folks. I wasn't as thrilled with his science as he was, although some of his findings were startling (e.g., men who had unloving, uncaring parents were much more likely to develop Alzheimer's than those who had warm, loving parents).

But I doubt his methodology would apply to people as a whole. This was an ultra-elite group of men. Far fewer Americans went to college before the end of WWII and the GI Bill, and only a tiny percentage got into Harvard--then and even now regarded as the top Ivy League School. A degree from Harvard then (and in some respects now) was (is) a door-opener to the upper middle class and the top of the grad's chosen field. Being a member of that tiny elite was no guarantee of a happy, successful life, but it sure helped.