Can people change? That is the question, it seems to me, at the dark heart of Mad Men. We’ve spent eight years watching Don Draper try to become a better man. He wants to drink less and swim more. He wants to get close to his kids and stay faithful to his wife.

But little has changed; Don remains mostly the same. The world around him is now wearing orange plaid and bushy sideburns, but Don still looks like an astronaut, clad in crisp suits and pomade hair. He’s still sipping bourbon in bars, still sleeping around, still most alive when selling himself to strangers. What we’ve learned from the passing of time is that Don has learned nothing.

I have no idea how Mad Men will end. Perhaps Don will have a midlife epiphany and move to California. Maybe he’ll find true love in the arms of a waitress from Racine. But given the pace of the show so far, I’d bet on a far less dramatic finale. If anything, the turbulence of the sixties only highlights the brittleness of human character. Fashions change. Politics change. A man can walk on the moon. But we are stuck with ourselves.

Is this true? Are we really stuck? Do people ever change? Put another way: is Don Draper the exception or the rule?

Obviously, the empirical answers are irrelevant to the success of Mad Men; the art doesn’t need to obey the facts of social science. But let’s admit that these are interesting mysteries, and that our capacity for change isn’t just relevant on cable television. It’s also a recurring plot point of real life.

The best way to grapple with these scientific questions is to follow people over time, measuring them within the context of a longitudinal study. And since Mad Men is a basically the longitudinal study of a single man over a decade, it might be worth comparing its basic conclusions – most people don’t change – with the results of actual longitudinal research.

The most fitting comparison is the Grant Study of Adult Development, which has been tracking more than 200 men who were sophomores at Harvard between 1939 and 1944. Every few years, the subjects submit to a lengthy interview and a physical exam; their wives and children are sent questionnaires; they are analyzed using the latest medical tests, whether it’s a Rorschach blot or an fMRI. The oldest subjects are now in their mid-nineties, making them a few years older than Don Draper.

George Vaillant led the Grant study for more than thirty years, and has written extensively about its basic findings. His first survey of the project, Adaptation to Life, is a classic; his most recent book, Triumphs of Experience, provides a snapshot of the men as they approach the end of life. And while Vaillant’s writing is full of timeless wisdom and surprising correlations – alcoholism is the leading cause of divorce; a loving childhood is more predictive of income than IQ scores; loneliness dramatically increases the risk of chronic disease - it’s most enduring contribution to the scientific literature involves the reality of adult development.

Because people change. Or rather: we never stop changing, not even as old men. In fact, the persistence of personality change is one of the great themes of the Grant study. The early books are full of bold claims. But then, as the years pass, the stories of the men become more complicated, subtle, human.

Take divorce. Vaillant initially assumed, based on his interviews with the Grant subjects, that “divorce was a serious indicator of poor mental health.” It signaled an unwillingness to commit, or perhaps an inability to deal with intimacy. These marriages didn’t fail because they were bad marriages. They failed because the men were bad partners, just like Don.

But time is the great falsifier. When the subjects were in their seventies and eighties, Vaillant conducted extensive interviews with them about their marriages. As expected, more than 90 percent of those in consistently happy first marriages were still happy. The same pattern applied to those stuck in poor relationships – they were still miserable, and probably should have gotten divorced. However, Vaillant was startled by what happened to those men who divorced and later remarried: roughly 85 percent of them said “their current marriages were happy - and had been for an average length of thirty-three years.” This data forced Vaillant to reconsider his beliefs about divorce. Instead of seeing marital failure as an innate character flaw, he came to believe that it was “often a symptom of something else,” and that these men had learned how to become good husbands. They changed.

The same idea returns again and again, both in the statistics and the individual case studies. The man raised in a loveless home becomes a loving father; the alcoholic stops drinking while another one starts; some gain wisdom, others grow bitter. The self is a verb, always becoming. As Vaillant writes, “Our journeys through this world are filled with discontinuities.”

Of course, longitudinal studies are not the only way to measure adult development. In a recent Science paper, the psychologists Jordi Quoidbach, Daniel Gilbert and Timothy Wilson came up with a novel way to measure our inner changes. The survey itself was simple: they asked more than 19,000 adults, ranging in age from 18 to 68 years, questions about how much they’d changed during the previous ten years and how much they expected to change over the next ten. By comparing the predictions of subjects to the self-reports of those who were older, the scientists were able to measure the mismatch between how much we actually changed (a significant amount) and how much we expected to change in the future (not very much at all.)

The scientists refer to this as the “end of history illusion,” noting that people continually dismiss the possibility that their personalities, values, and preferences will evolve over time. As the scientists write, “People, it seems, regard the present as a watershed moment at which they have finally become the person they will be for the rest of their lives.” But no such moment exists. History is never over, and we never stop changing.

In his writing, Vaillant repeatedly quotes the famous line of Heraclitus: “No man ever steps in the same river twice; for it is not the same river, and he is not the same man.” Mad Men shows us the changes of the river. It shows us a society disrupted by the pill and the civil rights movement and Vietnam. But Don remains the same, forever stuck in his own status quo. For a show obsessed with verisimilitude – every surface is faithful to the period - this might be the most unrealistic thing on the screen.

Vaillant, George E. Adaptation to Life. Harvard University Press, 1977.

Vaillant, George E. Triumphs of Experience. Harvard University Press, 2012.

Quoidbach, Jordi, Daniel T. Gilbert, and Timothy D. Wilson. "The end of history illusion." Science 339.6115 (2013): 96-98.