What cognitive advantages do young people have over me? Not as many as we once thought.
We once assumed that our brains grew until, oh say, our mid-twenties and then gradually declined until death. We had what we had and would never get any more. As cells died, they weren’t replaced. After reaching its peak, the brain was essentially static – it couldn’t grow or enrich itself. It could only decay.
A new paradigm holds that the brain is plastic – it can grow and change and build new connections well into our mature years. It may even be possible to do brain exercises to improve our mental performance.
This model generally divides intelligence into two types: fluid and crystallized. Fluid intelligence is the ability to think critically and manage effectively in novel situations. People with fluid intelligence can reason their way through unfamiliar territory by recognizing patterns and relationships. They figure out stuff on the fly.
People with crystallized intelligence have valuable facts and data stored in their brains and know what to do with it. (I have some data and I know how to use it!) It’s all about what we’ve experienced, learned, and remembered over a lifetime.
Young people tend to excel at fluid intelligence. Why? They get more practice. Since they don’t have many experiences, a greater proportion of their experiences will be novel. When our 14-year-old niece spent a summer with us in Stockholm, everything was new to her. She experienced her first taxicab, her first subway, and her first molten chocolate cake. She had plenty of chances to hone her fluid intelligence.
Older people, on the other hand, tend to have more crystallized intelligence. I experienced my first subway long ago. I learned from the experience and stored what I learned somewhere in memory (where it crystallized). I can deal with subways because I know about them. I don’t need to spot new patterns; I already recognize them. As I deal with fewer novel situations, my fluid intelligence gets rusty.
Now, there’s a new, new paradigm of brain function. It’s not just fluid versus crystallized. Rather, there are multiple cognitive skills and they peak at different times in our lives.
The new view is exemplified in the work of Laura Germine and Joshua Hartshorne. Germine and Hartshorne have recruited thousands of people of all ages to play mental games at testmybrain.org and gameswithwords.org. The resulting data allow the researchers to identify different cognitive skills and relate them to different age ranges. (The original paper is here. A less technical overview is here).
Here’s a summary of what they found:
Peak mental processing speed occurs, as expected, in late teens and early 20s and declines relatively rapidly afterward. But other skills peak at different times. Working memory climbs in the late 20s to early 30s, and then declines only slowly over time. Social cognition, the ability to detect others’ emotions, peaks even later — in the 40s to age 50 — and doesn’t start to significantly decline until after 60. …. Crystalized intelligence, measured as vocabulary skills, didn’t have a peak. Instead, it continued to improve as respondents aged, until 65 to 70.
The finding that crystallized intelligence doesn’t peak until 65 to 70 seemed to contradict earlier studies. When Germine and Hartshorne analyzed earlier studies however, they found that the peak itself rose over time. Studies conducted in the seventies, for instance, suggested that crystallized intelligence peaked in the early 40s. Studies conducted in the eighties and nineties found a later peak: around 50. Studies conducted since 1998 showed an even later peak: around 65. So, perhaps, our entire society is getting smarter.
So don’t assume that my brain is declining as I age. Rather, in Germine’s phase, it’s ripening. Maybe yours is, too.