Shouldn't "intelligence" increase as we age?

Without getting sidetracked by hair-splitting definitions of what constitutes “intelligence,” why don’t humans become more intelligent, as we age?

Recent imagining studies conclusively demonstrate that brain activity stimulates the formation of new, denser, more efficient neural pathways. Generally accepted studies on human intelligence suggest that cognitive ability is strongly associated with efficient neural pathways and the unimpeded transmission of signals. Nowhere have I read that these neural pathways die off, in large amounts, as part of the natural aging process.

What gives?

Evolution didn’t prepare us for medical advances that would keep us alive for nearly a century. We really weren’t built to last this long-- once you’re past breeding age, you’re pretty much redundant. Our organs, including the brain, sort of “burn out” because there was no incentive for evolution to make them regenerating. The goal is reproduction, not a long life.

We constantly lose brain cells, and therefore slowly lose intelligence as we age, compensated for by the fact that we learn about the world.

I sort of agree, but I think it would be reasonable to argue that from an evolutionary standpoint, having successful grandchildren is as important as having successful children of your own.

We do, to a point. Its not huge though.

"Actually, certain mental functions increase slowly and slightly after the age of 16, peaking in the 20’s, with others remaining stable or even rising slightly up to the age of 60 or so. With some individuals, vocabulary may increase over time. "

The important thing to remember is that an ‘IQ’ score is actually measuring how ‘intelligent’ you are compared to other people in your age range - its a relative score, not an absolute one. The reason for this is that its intended to be a diagnostic tool, ie to tell us if a person is doing particularly well or badly on cognitive tasks compared to other people in the same age range. We need to account for age because people do change over time and comparing a 40 year old to a 20 year old isnt very helpful usually - they have a 20 year head start after all. The difference isnt large but its enough to potentually interfere with what IQ tests are generally intended for.

The thing is though, on average any age related change in intelligence will be similar for other people in your age range, so your score ends up as pretty much the same as it was at 20, even though your actual ‘intelligence’ does change over time to a certain extent. That is, if Tom was smarter than me in high school, theres a fair chance he’ll be smarter than me at 40, even though we’ve both got smarter since high school.

I hope that makes some kind of sense, my head is starting to hurt.


Recent studies also show that exercising your leg muscles makes them stronger. So why is it that letter carriers don’t get stronger and stronger legs over the years until they retire? Or perhaps they do?

I would think that a 20-year-old who joins the postal service would get stronger and stronger legs for the first few months, but eventually, down the road, the process would level off and then reverse itself as other factors (i.e. physiological limitations and aging) start to slow down the process and ultimately work against him.

I think it’s same thing with your brain.

Just guessing though.

Sure, but the only genetic way to have grandchildren is to have children. After that, your gene production isn’t directly involved any more.

Nurturing is useful, of course, but in social animals like man, it can be done by someone else just as easily.

Have you recent cites to corroborate your claims–claims that directly contradict recent imaging studies that show increased neural pathways?

Sure, but in our environment of evolutionary adaptability (EEA) limited resources and the means to gather such resources may have put more of the pressure for upbringing on the parents rather than grandparents.

Food for thought…

A Decade of Discovery Yields a Shock About the Brain
January 4, 2000 New York Times


As scientists look back at all the discoveries made in the 1990’s, the so-called Decade of the Brain, one finding stands out as the most startling and, for many scientists, the most difficult to accept: people are not necessarily born with all the brain cells they will ever have.

In fact, from birth through late adolescence, the brain appears to add billions of new cells, literally constructing its circuits out of freshly made neurons as children and teenagers interact with their environments. In adulthood, the process of adding new cells slows down but does not stop. Mature circuits appear to be maintained by new cell growth well into old age…

Although the Congressionally mandated “Decade” produced many other discoveries, from ways to obtain images of fleeting thoughts inside a person’s head to new drugs for a wide variety of mental disorders, the finding that the brain develops and maintains itself by adding new cells is the most revolutionary. …

Some researchers have begun isolating special cells that continue to divide and produce new brain tissue, with the hope of implanting such cells into areas of the brain that are damaged by disease or accidents.

For decades, it was axiomatic that people were born with all the brain cells they would ever have. Unlike the bones, the skin, the blood vessels and other body parts, where cells divide throughout life to give rise to new cells, it was believed that the brain did not renew itself.

Though the brain did add vast amounts of new connections early in life and could compensate somewhat for many injuries, it was thought that no one could be expected to grow more brain cells with age. Quite the opposite. People were told that the only thing they could look forward to was gradual mental deterioration as cells died off and were never replenished.

These ideas were so firmly established that many scientists have a hard time believing the findings, reported in the last couple of years by a number of investigators, that the human brain makes new cells after birth, said Dr. Fred H. Gage, a neuroscientist at the Salk Institute in La Jolla, Calif.

Not sure…

It seems to me that most teenagers I have encountered know _everything, and I, the parent, know nothing.

There is also the effect of decreased blood circulation to the brain reducing its effectiveness.

I recall reading of a writer (Robert Heinlein?) who had surgery to fix constricted arteries that were restricting crainal blood flow. The surgery was successful, and besides the good effects on his health, critics noted that the books he wrote after this surgery were much better than recent ones before the surgery. The books were said to be as good as the ones he had written in his prime.

I think that intelligence might be fairly defined as the ability to handle new things: Come up with new ideas, learn the new ideas others have come up with, etc. For this, having a lot of neuron connections wouldn’t be so important, as forming new ones. So even if new connections are always being formed, if they’re formed more slowly in older folks, then the older folks might be said to be less intelligent.

Yes, this is true, but give them a few years. As they get older, you will be astonished at how much smarter YOU become! :wink:

Studies (and conventional wisdom) suggest that age and exceptional creative insight (aka brilliance) largely depends on the field of study. You may be correct in youth being an asset in theoretical physics, but for researchers in the humanities, or the social or behavioral sciences, the ability to brilliantly connect dots is largely dependent on the acquisition of a massive knowledge base–combined with intellectual rigor, of course.

Someone above suggested arteriosclerosis in older brains as a major limiter. But this condition isn’t the norm in adults in their 30s and 40s.

From what I’ve been reading, the problem isn’t necessarily neuron loss (though that happens with some people) but a change in the way the brain communicates as we get older.

This site says: (Warning PDF)

There are also physical changes in the brain: