What can 268 men from the Harvard Class of 1944 teach us about a successful life?

A lot, apparently. These men were part of one of the longest and most comprehensive longitudinal studies, called The Grant Study, ever conducted. The study began in their sophomore year of Harvard Medical School – and continues to this day. The men were observed, studied, interviewed, examined and tracked over time.

And it proved that John Lennon got it right when he wrote All You Need is Love.

George Vaillant chronicled the work in his book, Triumphs of Experience: The Men of the Harvard Grant Study. Granted, these gents are not a random sampling – the group is all male, highly intelligent, and afforded the opportunity to attend one of the most prestigious universities in the world. Nonetheless, the findings are compelling – and I suspect, universal.

The men were followed closely over the course of their lifetimes. Over the last seventy five years, they have participated in physicals, psychological evaluations, comprehensive face-to-face interviews every 10 to 15 years, and annual exhaustive questionnaires. In addition, researchers interviewed their parents and three generations of relatives.

The study was organized around a concept called the Decathlon score – ten accomplishments that included career success, professional prominence, mental and physical health, social and familial relationships, and overall happiness.

From George Vaillant:

The results were as clear-cut as they were startling.

We found that measures of family socioeconomic status had no significant correlation at all with later success in any of these areas. Alcoholism and depression in family histories proved irrelevant to flourishing at 80, as did longevity. The sociability and extraversion that were so highly valued in the initial process of selecting the men did not correlate with later flourishing either.

In contrast with the weak and scattershot correlations among the biological and socioeconomic variables, a loving childhood—and other factors like empathic capacity and warm relationships as a young adult—predicted later success in all ten categories of the Decathlon. What’s more, success in relationships was very highly correlated with both economic success and strong mental and physical health, the other two broad areas of the Decathlon.

In short, it was a history of warm intimate relationships—and the ability to foster them in maturity—that predicted flourishing in all aspects of these men’s lives.

We found, for instance, that there was no significant difference between the maximum earned incomes of the men with IQs of 110–115 and the incomes of the men with IQs of 150-plus. On the other hand, men with warm mothers took home $87,000 more than those men whose mothers were uncaring. The men who had good sibling relationships when young were making an average of $51,000 more a year than the men who had poor relationships with their siblings. The 58 men with the best scores for warm relationships made an average of $243,000 a year; in contrast, the 31 men with the worst scores for relationships earned an average maximum salary of $102,000 a year.

So when it comes to late-life success—even when success is measured strictly in financial terms—the Grant Study finds that nurture trumps nature. And by far the most important influence on a flourishing life is love. Not early love exclusively, and not necessarily romantic love. But love early in life facilitates not only love later on, but also the other trappings of success, such as high income and prestige. It also encourages the development of coping styles that facilitate intimacy, as opposed to the ones that discourage it. The majority of the men who flourished found love before 30, and the data suggests that was why they flourished.

A deeper dive into the results point to the importance of a variety of relationships in our lives – from early childhood on. And from parents, siblings, grandparents and partners. And there are two elements – the men that flourished most were those that were loved and could love.

So the study leads me to these questions:

• What are you doing to nurture relationships in your life?
• What more could you do – for your own sake and that of others?

(A special thank you to Matt Hogan for sharing this study with me!)