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How Does Our Intelligence Change Throughout Our Lifespan?

  • Writer: Patricia Faust
    Patricia Faust
  • May 9, 2019
  • 4 min read

The definition of human intelligence from the Encyclopedia Britannica is: “mental quality that consists of the abilities to learn from experience, adapt to new situations, understand and handle abstract concepts, and use knowledge to manipulate one’s environment”. The world of brain function and brain health has been turned on its ear over the past twenty years or so. When the understanding of neuroplasticity and neurogenesis became mainstream and initiated different paths of research, there was research that was spawned in the area of intelligence.


The Categories of Intelligence

More than seventy years ago, psychologist Raymond Cattell and his student John Horn put forth the proposal that intelligence was not one specific thing but instead was a collection of various abilities working together. This idea was called the Cattell-Horn theory which stated that these different abilities could be classified into two categories: fluid intelligence and crystallized intelligence. These two categories composed general intelligence. Fluid abilities allow a person to solve new problems and encode short-term memory. Crystallized abilities are born from knowledge and general information (K. Sukel, May 26, 2015). Cattell and Horn believed that both of these types of intelligence increased throughout childhood and adolescence. Fluid intelligence would peak in the early twenties but crystallized intelligence would go on and develop into the thirties and forties.


This had been the prevailing theory of intelligence for many decades. The overarching belief was that cognition couldn’t get any better after a certain age. Research in brain development centered on the premise that “the brain is mostly mature by 18 – and then there’s a little more maturation of the frontal lobe into your 20s. But once that happened, then, it was thought, you were done,” said Joshua Hartshome, a post-doctoral fellow at MIT. “So it fit with this idea that nothing was changing until older age.” And, in older age, cognitive decline was occurring. The discovery that the brain was far more plastic (malleable) than believed, researchers at MIT wondered if there was more to cognitive peaks across the lifespan than had formerly been investigated.


The Research on Fluid and Crystallized Intelligence

Fluid and crystallized intelligence do change throughout our lives, with certain mental abilities peaking at different points. Past research indicated that fluid intelligence peaked early in life but it has been discovered that certain aspects actually peak as late as age forty. Crystallized intelligence continues forward with a peak around age sixty or seventy. There is evidence to support that certain abilities peak at certain times. With this new understanding come new questions. What kinds of abilities are changing, why are they changing, and what’s driving those changes?

Where else does research in this field lead us? Researchers from Brisbane, Edinburgh, and Aberdeen revisited a study of 2000 people who had IQ tests in 1932 and 1947 and revealed that one-quarter of the participants’ change in intelligence was due to genetic factors. This study also revealed that the largest influence on changes in intelligence is environmental. These findings spurred researchers into looking at what are the roles of genetics and environmental factors in determining our intelligence and how it changes across peoples’ lifetimes (Science in Public, 2012). Studies over the years since early 2000, have shown that people who took intelligence tests as children and then again in old age, tended to keep about the same relative score. But, there was also some change: some who scored well in early tests went down a bit, and those who scored low early did better in old age. Now researchers want to know what drives these changes in lifetime cognitive aging (Science in Public, 2012).


The Effect of Genetics and Environment on Intelligence

Professor Peter Visscher from Queensland Brain Institute noted that “Identifying genetic influences on intelligence could help us understand the relationship between knowledge and problem solving and an individual’s outcomes in life, and especially to understand why some people age better than others in terms of intelligence.” Researchers went back to the participants tested for intelligence in 1932 and 1947 and were able to get DNA samples from approximately 2000 participants ranging from age sixty-five to seventy-nine. Scientists examined over a half a million genetic markers to work out how genetically similar the participants were, even though they were not related. Their results were not especially significant but did provide data that was never available before. Never before did they have information that gave an estimate of how much genetic differences affect intelligence changes across the lifetime. Professor Deary of the Edinburgh’s Centre for Cognitive Ageing and Cognitive Epidemiology states that “The results partly explain why some people’s brains age better than others”.


“This study also strongly suggests how important our environment is in helping us stay sharp as we age” states Professor Visscher. “It’s critical information because we know that intelligence is a predictor of many factors including lifespan, health, income. And, as our community ages we need to understand how we can predict and ultimately manage changes in cognitive thinking. Ultimately, understanding the influence of genetics in a healthy brain will help us understand and combat the changes caused by disease like dementia.”


References:

Cherry,K. (July 12, 2015). Fluid intelligence vs. crystallized intelligence. Retrieved March 3, 2016 from http://psychology.about.com/od/cognitivepsychology/a/fluid-crystal.htm


Human intelligence. Retrieved March 2, 2016 from http://www.britannica.com/print/article/289766


Science in Public (January 19, 2012). How does our intelligence change through life. Retrieved March 3, 2016 from http://www.scienceinpublic.com.au/other/how-does-our-intelligence-change-through-life


Sukel,K. (May 26,2015). Maturing intelligence. Retrieved March 2, 2016 from http://www.dana.org/News/Maturing_Intelligence/

 
 
 

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March was an unusual month for me.  Normally I work on articles, give presentations and generally just stay tuned to what is going on in the field of aging.  This month I “learned” a lot.  Last year I learned how to write a book.  At the time I took the course I thought it would just be a natural extension of all the writing I had done over the years.  WRONG!!  The actual writing of the book was the easy part.  Putting it together into a book was difficult for me.  The course gave me step by step lessons on constructing a book.  Then editing and formatting were just as challenging.  On June 7 last year the book was published!  It was one of the most satisfying days of my writing career. 

Naturally, when you self-publish, you do not have a publisher promoting the book and getting it in the right categories for best sales on Amazon.  That was crushing because I really didn’t know to appropriately market it.  I am a brain health person!  In December of last year, I purchased a marketing program that is based on statistics.  I am technical minded and so this approach made sense to me.  The course is almost completed.  Can’t wait to see if it improves sales!

The next step I am looking at is recording an audiobook.  This is another venture I knew nothing about.  But I am already tagged on Facebook for marketing of audio book programs.  Facebook picks up everything.  Now my husband was creative director for an advertising agency and when I told him I purchased another class – he couldn’t believe it.  “This was my business.  I know how to do recordings, why didn’t you ask me?” Well, I knew he was an expert in that business, but this audiobook needs to meet all the criteria that Amazon requires for publication.  So, he can take care of the recording part of this audiobook, and I will navigate the process of meeting Amazon’s requirements.  We worked on the book together like this. 

Then I talked with some coaching experts on the viability of starting group teaching programs.  Reading The Boomer Brain book and implementing the Brain Healthy Lifestyle have two entirely different outcomes.  This lifestyle is important to maintaining high cognitive function throughout the later years of our lives.  Look for updates as to when I will roll this program out.

My last learning endeavor was attending a two-day bootcamp for Speakers.  I am really excited about what I learned there.  That is a late this year or next year project, but it is one I am really looking forward to.

 

What Is Happening in April?

The American Society on Aging is having their annual conference in Orlando Florida April 21-24.  This is the largest multidisciplinary conference on aging and the annual conference for Members of ASA.  I have attended a number of these conferences throughout the years, and it is consequential.  Keynote speakers and special events are focused on combating ageism in our society.  Although this is a professional meeting, the attendees come from all aspects of aging services.  They have their work cut out for them this year!

April is Stress Awareness Month.  We should be aware of stress every month and understand how we can break the stress cycle.  These are stressful times, and we need to protect ourselves

Here is a positive one “April is National Volunteer Month”.  When I am working with new retirees who don’t know what to do, I talk to them about volunteering. It is important to have a purpose after you leave the workforce.  There are so many nonprofits who need help in all aspects of their organizations.  It is a perfect way to give back.

Finally – It was Opening Day for the Cincinnati Reds – the oldest major league team in the nation.  Cincinnati takes that responsibility seriously.  There is always an Opening Day Parade through downtown to the Ball Park.  Huge crowds line the streets and every year there is talk of making it an official holiday.  Schools and employers look the other way when there is an empty desk.  No matter what the outcome of the game is, there is so much joy, and you can feel that energy.  I am fortunate that I get to experience that.  We all need some joy right now. 

Enjoy your April.

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