At what age do we reach maximum intelligence?

In 1905, Albert Einstein had his so-called "miraculous year": he wrote five influential scientific investigations including, for example, the most famous equation in the history of science (E = mc2).

He was only 26 years old.

"My PhD supervisor, a brilliant and inspiring man, jokingly told me that his career was complete and that it was up to me to make the discovery that would give the Nobel Prize to our team," says the astrophysicist. Sabrina Stierwalt podcast "Everyday Einstein".

The teacher's comparison between "the miraculous year" of Einstein and his young pupil not only served as motivation.

It is also accepted by society that cognitive abilities reach their maximum at age 18, then begin their inexorable fall.

This idea is reinforced by the fact that, over the years, the brain is deteriorating and, at the same time, the ability to create, reason and memorize information.

But does this mean that young adults are at the peak of intelligence? What about the value of the experience accumulated over the years?

The answer depends on what you measure and when.

Capacities by age

"At any age, some things improve, some more and others," said Joshua Hartshorne, senior author of the largest study on cognitive abilities related to age , told MIT News.

Hartshorne's work, published in 2015 by the journal Psychological Science, evaluated more than 48,500 people through a series of online tests, and then cross-referenced information with in-person experiences in small groups.

According to the study, "some skills reach their peak and begin to decline after high school, some skills stagnate early in adulthood, begin to decline in the 30s, others do not. reach their peak only 40 years or later. "

For example, the rapid processing capacity of information reached its peak at 18 and 19 years of age.

At age 25, however, the maximum is reached in short-term memory, which remains for a decade before starting to decline.

And the ability to understand the emotions of others does not reach its fullness until after 40 or 50 years.

In fact, this joint research conducted by Harvard University and MIT showed that some were reaching their peak in old age.

Unlike previous studies, in vocabulary tests (word definition), those with the best results were those aged 65 to 75 years.

"We were mapping when these cognitive abilities peaked and we found that there was not a single peak for all skills, they were everywhere," Hartshorne adds to MIT News.

Fluid versus crystallized

Stierwalt explains in his podcast that these discoveries are due to the fact that our intelligence has many facets.

On the one hand, he said, "we have a fluid intelligence, which is our ability to think quickly, solve new problems and identify patterns."

It is the one who, in general, knows its heyday among young people.

But, he continues, "we also have what psychologists call crystallized intelligence, which reflects our acquired knowledge and our ability to build relationships with our environment."

It is there that the experience of years is what weighs the most.

IQ tests usually measure the first type of intelligence and that is why, over the course of history, different studies have shown that young people perform better than adults.

However, according to the psychologist Phillip L. Ackerman in a study published in the Journal of Gerontology in 2016, "many intellectually demanding tasks in the real world can not be accomplished without a broad repertoire of declarative knowledge and procedural skills" .

In other words, he says, no one would ask the rookie with the highest IQ to perform a cardiovascular operation in front of an expert of average age.

A first-year university student should also not carry out a doctoral dissertation at a level comparable to that of another with a higher academic background and empirical experience, he adds. .

Therefore, Ackerman insists that we should not confuse knowledge and intelligence.