This is the type of intelligence that makes older workers valuable

One need look no further than Silicon Valley for evidence that older workers are judged as less sharp—and less productive—than their younger peers, despite mounds of research suggesting the opposite.

Now, a new brief from the Center for Retirement Research has synthesized the research on aging and cognitive ability to illustrate how older workers, who are living and working longer than ever before, maintain productivity as the age—even as their natural capacity to process new information diminishes over time.

The answer, according to co-authors Anek Belbase and Geoffrey T. Sanzenbacher, is that older workers make up for a decline in “fluid intelligence”—the ability to solve new problems—with “crystallized intelligence,” or the learned knowledge and experience they accumulate over the years.

Younger workers operate when their fluid intelligence is at peak levels, which makes it easy for them to learn the new skills necessary to do their jobs. Pharmacists-in-training, for example, must employ their fluid intelligence during their schooling and early career to learn vast amounts of unknown facts and procedures. But as these pharmacists gain experience in their jobs, they rely more on their crystallized intelligence. They have accumulated a large body of knowledge over time, and thus they have less of a need to learn new information.

Belbase and Sanzenbacher point to 2012 study from Timothy Salthouse, director of the Cognitive Aging Laboratory at the University of Virginia, which found that the cognitive abilities that decline with age don’t necessarily impair real-world functioning. The ability to complete a New York Times crossword puzzle, for instance, increases with age, suggesting that adults are able to deepen their cognitive function with experience and knowledge.

The ability to take advantage of crystallized intelligence is true not just for higher skilled workers, but also those in clerical positions. That’s because many activities in such roles tend to become automatic over time, so workers are able to build up a reserve of fluid capacity that protects against decline, write Belbase and Sanzenbacher.

There are, however, some exceptions. Workers in certain high-skilled fields that demand greater levels of fluid intelligence can’t necessarily perform as well as their younger counterparts. In a 2009 study of US air traffic controllers, researchers found that older, experienced controllers (ages 53-64) asked to re-route two planes headed for a collision took roughly the same amount of time to perform the task as their younger, inexperienced counterparts (ages 20-27). By contrast, young, experienced controllers took less than half the time. The research undergirds the US Federal Aviation Authority’s requirement that air traffic controllers retire by the age of 56.

Problems do arise, however, when aging workers begin to experience even mild symptoms of dementia, according to several studies on Alzheimer’s disease and dementia. Belbase and Sanzenbacher recommend that, in fields where cognitive demands are high, or ones that could result in significant harm to others, like surgery, workers over age 60 should be screened for cognitive decline.