In most fields, professional decline starts earlier than almost anyone thinks. Research by Dean Keith Simonton, professor emeritus of psychology at UC Davis, shows that success and productivity increase for the first 20 years after the inception of a career. Therefore, if your career kicks off at age 30, you will reach your pinnacle around 50 and go into decline soon after that.

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.

The author of those gloomy lines? Paul Dirac, a winner of the 1933 Nobel Prize in Physics.

Is it inevitable that the result of this is a loss of happiness?  Garnering your sense of self-worth from your professional successes certainly seems an increasingly precarious road to tread as we age; with professional decline comes the potential for a terrifying loss of identity.  However, in this essay for The Atlantic, social scientist Arthur C Brooks finds that this does not have to be the case. In a four-year quest, he found how to turn his potential deterioration from a matter of dread into an opportunity for progress.

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.

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