Fluid Intelligence vs. Crystallised Intelligence

Recently, I realized something, I had subconsciously known for a very long time.
My wife is ‘naturally’ smarter than me.
It is kind of annoying. At the end of the day, I have got a Ph.D. and she doesn’t :).
But no matter how I look at this, at least in some situations my brain is not exactly a match for hers.

Her intellectual superiority manifests itself frequently in novel situations which require quick, logical thinking and abstract reasoning that cannot be supported by background knowledge and experience.
She arrives often at more imaginative solutions than me in a shorter time.

How could this be explained?
What does it have to do with young children and reading?

My wife’s intellectual ability is a typical example of fluid intelligence described 50 years ago by a psychologist Raymond Cattell. Horn and Catell (1967) defined fluid intelligence as:

the ability to perceive relationships independent of previous specific practice or instruction concerning those relationships

It is the form of intelligence which is independent of education. My wife would still have a high level of fluid intelligence even if she had not done undergraduate degree or masters.
It is a biologically-driven component of intelligence (inherited).
Fluid intelligence helps when people face entirely new problems.
It can be associated with abstract thinking, creativity, and innovation.

Unfortunately, there is very little we can do to improve fluid intelligence.
It is a component of intelligence closely related to ‘working memory’ which helps retain information when this information is not readily present at our fingers tips. People who have a high level of fluid intelligence are also able to remember and manipulate longer sequences of numbers (e.g. 7, 21. 34. 66. 87. 17. 9. 77, 88, 899), remember facts easily etc. To improve fluid intelligence we would have to improve working memory.
Although some studies suggest it is possible  (e.g. influential study by Jaeggi’s on n-back tasks) many researchers dismiss this idea. It is possible that what we get when we are born, it something we have to live with.

On the other hand, the component of intelligence which I (hopefully) exemplify was described by Catell as crystallized intelligence. It is an acquired component of intelligence. It is intelligence based on knowledge in specific domains (languages, statistics). People with a high level of crystallized intelligence are good at reading comprehension, standardized test, verbal skills. It is intelligence based on previous discoveries, experiences, and knowledge. It is like ‘standing on the shoulders of giants’.

Although it sounds like an inferior component of intelligence, research suggests it predicts positively academic learning and professional success. It also supports learning facts, numerical understanding, information, figures, and vocabulary, and social skills. It can be easily developed (education) and is supported by long-term memory which is more or less limitless.

When we talk about ‘fluid intelligence’ and ‘crystallized intelligence’, we have to remember that humans intelligence is the sum of both. They are complementary since most of the problems we solve require both types of intelligence.

Fluid intelligence’ has its peak at age of 30-40. Then it seems to decrease.
Crystallized intelligence peaks at age of 70-80. What happens later probably does not matter that much.

Sometimes parents ask me if they can make their children smarter or what kind of ‘intelligence’ is better.
I am not an expert on ‘intelligence’.  I don’t value really one intelligence over the other either.
I have rather a simplistic view on it.

I tend to think that if we want to make our children smarter,  we need develop children’s knowledge,  vocabulary, provide rich educational experiences which improve children’s abilities to use words and numbers. On the top of it,  we need to teach children critical thinking, independent learning, creativity. The list could go on and on.

Will it benefit children’s fluid intelligence? Probably not.
Will it develop children’s crystallized intelligence? Definitely!
Is there another way to make children smarter? I wish I knew it.


Horn, J. L., & Cattell, R. B. (1967). Age differences in fluid and crystallized intelligence. Acta psychologica26, 107-129.

Jaeggi, S. M., Buschkuehl, M., Jonides, J., & Perrig, W. J. (2008). Improving fluid intelligence with training on working memory. Proceedings of the National Academy of Sciences105(19), 6829-6833.

Knox, A. B. (1977). Adult development and learning. San Francisco: Jossey-Bass.

Melby-Lervåg, Monica; Redick, Thomas S.; Hulme, Charles (2016-07-29). “Working Memory Training Does Not Improve Performance on Measures of Intelligence or Other Measures of “Far Transfer””Perspectives on Psychological Science11 (4): 512–534.