Many recent studies place a cap on our mental abilities at ridiculously young ages — some of the most current research reports cognitive peaks in young adulthood, and, no exaggeration, some go so far as to say late adolescence. From there, many scientists imply, it’s just a slow and exhausting descent into dementia. It's refreshing, then, to learn of a team of researchers who come to far different conclusions. Their recent work indicates aspects of our intelligence peak at different ages and stages, with some of our abilities rising to their heights only once we have reached our 70s.  

In fact, not only is there no single age at which we perform at peak levels for all mental tasks, there may not be a stage when we are best at most tasks.

“A lot of abilities — like processing speed or memory — peak relatively early in life. But our ability to use all the skills and knowledge we’ve accumulated over a lifetime (called crystallized intelligence) peaks much later,” Dr. Joshua Hartshorne, co-author of the research and a postdoc at MIT's Department of Brain and Cognitive Sciences, told Medical Daily. “In fact, crystalized intelligence continues to accumulate quite late — at least as measured by vocabulary, it continues to accumulate almost as late as American life expectancy!”

Web-Based Study

It’s tough work studying how mental abilities change with time because it’s difficult to get large numbers of people to come to a psych lab and participate in experiments. Hartshorne and his co-author Dr. Laura Germine confronted that problem head on by running large-scale experiments on the Internet. They created two web sites, gameswithwords.org and testmybrain.org, that feature cognitive tests which can be finished in just a few minutes. Over the past several years, they accumulated data from nearly three million people through these sites.

“One of the exciting things about this work (I think) is that we've shown that by using Web-based quizzes,” Hartshorne explained to Medical Daily, “we can study development and aging at a level of detail that wasn't really possible before.”

Analyzing the gathered data, the researchers found a very clear picture showing that each tested skill peaked at a different age. For example, raw speed in processing information appears to peak around age 18 or 19, then immediately begins its decline. Meanwhile, short-term memory continues to improve until around age 25, when it levels off and then begins to drop around age 35. However, other skills reach their heights later.

“Social perception continues to get better well into middle age, and it doesn't decline much with age after that. This suggests that older adults may be in a particularly good position to read and understand others,” according to Hartshorne.

Most surprisingly, their data identified a peak in vocabulary during the late 60s or early 70s, in stark contrast to the Weschler IQ test, which points to the late 40s.

“Vocabulary is peaking later and later with each generation,” Hartshorne commented in his email to Medical Daily: “So either we are getting better at learning or remembering words, or we are continuing to encounter new words much later into life than previously.” He and Germine believe this may be a result of better education, more people having jobs that require a lot of reading, and more opportunities for intellectual stimulation for older people.

Meanwhile, the two researchers search for ways to apply and deploy their new findings. While the results may not cleanly map onto policy recommendations, it “should be obvious why, as we better understand how ability changes over the lifespan, we'll be in a better position to design (lifelong) education, plan careers, and so on,” Hartshorne said.

Still, he offers one caveat: The need to keep individual variation in mind. Some teens may have better social perception than some middle-aged people, while, conversely, some 40-somethings may be faster on their feet than some 20-year-olds. Isn’t it time to legislate against ageism, along with the increasing tendency to belittle older workers?

“Tom Brady is well past the typical peak age for a football player,” Hartshorne said. “I'd still rather have him as my quarterback than pretty much anyone else.”

Source: Harshorne J, Germine L. When does cognitive functioning peak? The asynchronous rise and fall of different cognitive abilities across the lifespan. Psychological Science. 2015.