Physics and the Aging Brain

We are occasionally going to reprint articles by contributors to this website that still have relevance but were written some years ago. This piece was originally published in one of the first online magazines, Feed, in October of 2000. We have not updated the piece, but it did not seem to need much updating. Indeed, this article may be of more interest for us today now that we are undeniably in possession of aging brains. But do understand that whenever the word “recently” is used here it should be understood as “a quarter of a century ago.”

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Age of course imposes a number of penalties upon us: We lose muscle tone. Our reflexes slow. We require reading glasses. Our hair thins. We lose an appreciation for the profundity of rock lyrics. The question -- a crucial question for those of us who value our wit as much as our abs -- is whether a decline in intelligence belongs on this dispiriting list. The best evidence that it does has always been the effect aging has upon those who depend most on high-intensity mental gymnastics: chess masters, for example, or lyric poets, or inventors, or mathematicians, or, to choose the classic example, physicists.

Paul Dirac, who won the Nobel Prize in physics at the age of thirty-one for work he completed when twenty-five, put that evidence into verse:

Age is, of course, a fever chill
That every physicist must fear,
He's better dead than living still
When once he's past his thirtieth year.

Newton had invented calculus and worked out the basics of his laws of motion and his theory of gravity before he turned twenty-five (though the Principia Mathematica did not appear until he was forty-four). Einstein's general theory of relativity, probably his greatest achievement, was published when he was thirty-six; however, Einstein had published his special theory of relativity, along with the work on the photoelectric effect for which he would win the Nobel Prize, when he was only twenty-six. "A person who has not made his great contribution to science before the age of thirty," Einstein himself once stated, rather bluntly, "will never do so." Heisenberg came up with quantum mechanics at age twenty-three, the uncertainty principle when he was twenty-five.

Great work, blessedly, appears to get done later in life in fields where that work goes slower and seems less dependent upon sudden bursts of brilliance: history, for example, or geology, or writing novels. Tolstoy completed War and Peace and wrote Anna Karenina in his forties. Dostoevsky finished The Brothers Karamazov when he was fifty-nine. Goethe published The Sorrows of Young Werther when he was in his twenties, but the second volume of his long, dramatic poem, Faust, was completed as he entered his eighties.

Still, in fields where, as in physics, a mind must be able to juggle very many concepts very rapidly that disturbing drop off is hard not to notice. Bobby Fischer won the world chess championship at the age of twenty-nine and surrendered it at thirty-three. Anatoly Karpov took over that title at twenty-four and held it until, at thirty-four, he was defeated by twenty-two-year-old Gary Kasparov. (Kasparov himself was thrity-four when he lost to a ridiculously young IBM computer.)

New technologies also tend to leap out of young minds. Thomas Edison invented the phonograph at the age of thirty, the electric light at thirty-two. Guglielmo Marconi had produced a working "wireless telegraph" by the time he was twenty-one; Philo Farnsworth was the same age when he assembled a functioning electronic television. Alan Turing first raised the possibility that a machine might perform logical operations -- the possibility of designing, in other words, a computer -- in a paper published when he was twenty-five.

Robert Kanigel of MIT, author of a wonderful biography of a mathematician, The Man Who Knew Infinity, reports that in that field "it's part of the culture, it's accepted, that a mathematician in later years -- after the late thirties or forties -- is washed up." This sense that we hit a chronological, cognitive "wall" is certainly part of the culture in theoretical physics, too, though it can be hard to get physicists, a group not prone to sharing anxieties, to admit it.

"Nobody likes to think that they have gone past their peak," notes Alan Lightman, who was an astrophysicist at Harvard when he did admit to thinking precisely that in a melancholy 1984 New York Times "About Men" column. "It's a very unpleasant feeling," he explains. "Physicists, like athletes, are people who are superior to the average person at something. They get a lot of their self-identity from that special ability. It is very painful to come to the realization that you're not as good at it as you once were." (Lightman himself moved on to an enterprise at which it seems possible to be good longer. He published a well-regarded novel, Einstein's Dreams, in 1993; another novel, The Diagnosis, has just appeared.)

"None of my fragile childhood dreams, my parents' ambitious encouragement, my education at all the best schools," Lightman had written in that Times piece, "prepared me for this early seniority, this stiffening at 35."

Physics programs certainly don't offer seminars on how to cope with mental "stiffening at 35." "No one mentions it explicitly," acknowledges one somewhat older graduate student at Princeton, "but because the mythology of the famous physicists who did their work young is so strong, it is definitely in the atmosphere." It doesn't help that among the new graduate students in physics at Princeton it is not uncommon to find a teenager.

ANECDOTES ABOUT BRILLIANCE in twenty-somethings and impressions of stiffness in thirty-, forty- or fifty-somethings do not, however, prove the existence of that chronological wall. Statistics have, therefore, been deployed, studies made. The best is probably a "historiometric" survey of more than two thousand well-known scientists by Dean Keith Simonton. It appears to take us as close as we can currently get to an answer to the question of whether and when scientific ability declines.

Simonton, the most respected researcher in this field, concludes that individuals in physics, mathematics, and technology make -- on average -- their "best contributions" to their fields just before the age of forty. They make their "last major contribution" to those fields -- on average -- in their early fifties. Scientists in biology and the earth sciences, on the other hand, tend not to make their "last major contributions" until their late fifties.

The contrast with scholars in subjects like history and philosophy is more dramatic. Simonton's research shows that -- on average -- "they don't even reach their career peaks until they enter their sixties." (One assumes that individuals who write for online magazines will enjoy a similarly ascending trajectory.)

So there does indeed appear to be something about the ability to get the scoop on subatomic particles, dive into equations and give birth to new machines that fades -- relatively fast. That chronological wall does seem to exist, though we aren't likely to hit it quite as early as Lightman, not to mention Dirac, feared.

And before abandoning the blackboard, the aging physicist should remember that there have always been those whose careers are not average. Brian Greene of Columbia, who at thirty-eight says, "I'm hopeful that my best work is yet to come," points to the career of Edward Witten, eleven years his senior. Witten remains the leading figure in what is now the hottest field in physics, string theory. And there are more dramatic exceptions. Silvan S. Schweber of Brandeis is among those who cite "the remarkable Hans Bethe at Cornell, who is now working in a narrow area but still doing cutting-edge stuff in his nineties."

Exceptions. However, Schweber himself switched from physics to the history of ideas when he was about fifty. "I felt I was no longer being a creative physicist," he recalls. "Age was a part of it in the sense that there were striking new developments in my field, quantum field theory, but somehow I couldn't see them."

IF AGE DOES subtract some ability to "see" something in physics and related fields, the question becomes, why? Howard Gardner, a professor of cognition and education at Harvard, is among those who think the explanation has to do with our lives, not our brains. "I don't believe that there are cognitive limitations, strictly speaking, that prevent a mathematician or physicist from doing important work beyond thirty," says Gardner, author most recently of Intelligence Reframed. His advice for those who want to continue to produce major work as they age includes avoiding the sort of obligations that tend to come with age: "Don't get married and don't become head of the department or give lots of post-Nobel Prize speeches."

One forty-five-year-old physicist professor with two kids, a mortgage, and a working wife (though no post-Nobel Prize speeches to deliver yet), reports achieving a breakthrough in his work recently by staying up until four in the morning two nights in a row. "Those two nights were chosen carefully not to be before I had to teach or take the kids to school," he explains. "There aren't many safe nights like that." And still he paid a price in "increased stress and exhaustion" and "lack of patience with the kids." It was not always thus. "As a student and a postdoc," he recalls, "I routinely stayed up all night and that is when most of my good work was done. And anyway just doing it for a couple of nights is not what is required. What is required is total absorption in a problem."

If there is a physiological factor involved, some suggest it may be a decline in energy -- in the physical ability, for example, to pull those all-nighters. "When I was in my twenties, I could work on a problem for forty-eight hours straight without sleep," explains Lightman. "When we get into the forties and fifties, most of us don't have that kind of stamina."

Or, the physiological factor may be speed. We move less rapidly as we age; we even talk less rapidly. Is it surprising that we tend to think a bit less rapidly? And is the loss of some speed such a big deal? "Suppose you do get a little slower," asks Howard Gruber, an expert on the creative process and, at seventy-seven, the third oldest person interviewed for this article; "that doesn't have to stop you from doing the work." In chess, older players indeed perform quite well in matches that are not played against the clock.

And then there is the familiar stuck-in-their-ways theory. Young people are "more ready to accept the new," notes Gerald Holton, a seventy-eight-year-old Harvard physicist and historian of science, "because they didn't make their career on the old." Simonton, the master of historiometrics, has an interesting perspective on this. New ideas are formed, he maintains, out of "stray mental elements." As we age, Simonton says, those stray elements become "neatly packaged into a coherent way of looking at things." Too neatly packaged. "Instead of breaking new ground, new facts and concepts simply become assimilated to the developed scheme." That's no way to hatch radical new schemes.

The young are also more ready, as law enforcement officials know, to take crazy chances. Gardner, consequently, has this additional advice for "the sci-math type who wants to remain innovative at fifty: Be prepared to take big risks and fail, even if it takes ten years off your now reduced life span."

ALL OF US, with the exception perhaps of particularly shortsighted young people, want to believe that our minds retain their strength as we age. And given this rooting interest, the above explanations for the fall off in productivity in physics and related fields are actually rather cheering. Sure the distractions mount; sure we get a bit less energetic, a bit slower, somewhat more conservative. But these factors could, if we were sufficiently dedicated, be reversed, or at least compensated for: We could get divorced, drink more coffee, take more time, be braver. We could -- if we were prepared to return to the manias and instabilities of youth.

But some cognitive psychologists admit and some honest physicists mumble that maybe, in fact, we couldn't. There is evidence that something significant in our minds does decline with age. The best name for that something may be "working memory" -- which Wendy Rogers, who studies cognitive aging at Georgia Tech, defines as "everything you have active in your mind at one time." It is analogous, in other words, to a computer's RAM. Physicists, chess masters, and inventors presumably have to keep a number of thoughts -- "stray mental elements" -- in the air at one time in order to arrange them into new perspectives. The working memory is where that juggling takes place.

And what happens to our working memory as we age? This sort of thing is not easy to measure and compare, but, according to Rogers, it peaks in our twenties and declines continuously thereafter. Another expert in this field, Tim Salthouse of the University of Virginia, places the beginning of that decline in working memory "at about age thirty." Small difference. This is decidedly not cheering.

Something important in our minds goes as we age, the way our reflexes go. But just how depressing this loss should be is not clear. Did Einstein fail to produce momentous new theories after the age of thirty-six because his working memory wasn't what it used to be, or was the larger problem his stubbornness in rejecting quantum mechanics? We don't know. Can we compensate for a decline in working memory with deft use of a notebook or a notebook computer? We don't know.

We do know -- and here this article gets uplifting once again -- that there are also cognitive gains with age. "Your crystalized knowledge base -- what you know about the world -- continues to increase as you get older," Rogers reports. This is, in essence, the venerable and satisfying with-age-comes-wisdom argument. "The older person will have a richer repertoire to draw upon," is how it is put by Holton, who has published, by my count, six books in his seventies.

According to Hans Bethe, the oldest person interviewed for this article, "The main advantage of old age is that you have seen many things and learned many methods." Such knowledge is, undoubtedly, reward in itself, especially for those older folk who are not trying to wrestle with the geometry of string theory's eleven dimensions. And the discernment and expertise that presumably flows from having seen and learned a great deal has to be of some value even to those who are still intent on conjuring up new means of communication or waxing poetic on Grecian urns. It has to be of some value in theoretical physics, though we certainly don't have many examples of wizened, seventy-year-old physics whizzes to prove the point. (Holton, for his part, has been writing textbooks and books about science history and policy.)

We do, however, have Bethe himself -- a Nobel-Prize winner who helped develop both the atomic and hydrogen bombs, advised three presidents on arms-control issues, and who, at age ninety-four, continues to work productively in physics. Perhaps the last word on the decline of the ability to do physics with age should go to him.

"In a way I am not an exception," Bethe explains via fax. "My best papers were written at age twenty-three, thirty-two and forty-one. But I keep on producing, since science remains the most interesting occupation."