Darwin, Bach, and Professional Decline

What’s the difference between Bach and Darwin? Both were preternaturally gifted and widely known early in life. Both attained permanent fame posthumously. Where they differed was in their approach to the midlife fade. When Darwin fell behind as an innovator, he became despondent and depressed; his life ended in sad inactivity. When Bach fell behind, he reinvented himself as a master instructor. He died beloved, fulfilled, and—though less famous than he once had been—respected.

The lesson for you and me, especially after 50: Be Johann Sebastian Bach, not Charles Darwin.

How does one do that?

A potential answer lies in the work of the British psychologist Raymond Cattell, who in the early 1940s introduced the concepts of fluid and crystallized intelligence. Cattell defined fluid intelligence as the ability to reason, analyze, and solve novel problems—what we commonly think of as raw intellectual horsepower. Innovators typically have an abundance of fluid intelligence. It is highest relatively early in adulthood and diminishes starting in one’s 30s and 40s. This is why tech entrepreneurs, for instance, do so well so early, and why older people have a much harder time innovating.

Crystallized intelligence, in contrast, is the ability to use knowledge gained in the past. Think of it as possessing a vast library and understanding how to use it. It is the essence of wisdom. Because crystallized intelligence relies on an accumulating stock of knowledge, it tends to increase through one’s 40s, and does not diminish until very late in life.

Careers that rely primarily on fluid intelligence tend to peak early, while those that use more crystallized intelligence peak later. For example, Dean Keith Simonton has found that poets—highly fluid in their creativity—tend to have produced half their lifetime creative output by age 40 or so. Historians—who rely on a crystallized stock of knowledge—don’t reach this milestone until about 60.

Here’s a practical lesson we can extract from all this: No matter what mix of intelligence your field requires, you can always endeavor to weight your career away from innovation and toward the strengths that persist, or even increase, later in life.

Like what? As Bach demonstrated, teaching is an ability that decays very late in life, a principal exception to the general pattern of professional decline over time. A study in The Journal of Higher Education showed that the oldest college professors in disciplines requiring a large store of fixed knowledge, specifically the humanities, tended to get evaluated most positively by students. This probably explains the professional longevity of college professors, three-quarters of whom plan to retire after age 65—more than half of them after 70, and some 15 percent of them after 80. (The average American retires at 61.) One day, during my first year as a professor, I asked a colleague in his late 60s whether he’d ever considered retiring. He laughed, and told me he was more likely to leave his office horizontally than vertically.