The Difference Between Fluid Intelligence and Crystallized Intelligence

What is intelligence? There are plenty of ways to answer that question and all manner of different ways to try and measure it or to try and quantify it.

So far, the term has eluded a complete and comprehensive definition but one important distinction that we can generally agree on, is the difference between fluid intelligence and crystallized intelligence.

How Can Intelligence be Fluid?

When you think of someone you know that is intelligent, you might think of someone who knows an awful lot about history, politics and science. Perhaps you’re picturing someone who is a font of all knowledge and who is constantly impressing you with different facts and ideas.

But is this person really intelligent or are they in fact just knowledgeable? If you take someone with a low IQ and you spend years teaching them all about history and politics, then they would become a very knowledgeable person. But would that make them any better at math? At reasoning? Or at making smart decisions?

This is the difference between fluid intelligence and crystallized intelligence. Fluid intelligence broadly refers to the ability to think quickly and to come up with solutions to problems and novel ideas.

Meanwhile, crystallized intelligence refers to pure knowledge: this is all about how much you know rather than your ability to ‘use’ that information.

Which is Better?

So now you might be wondering what the difference between these two different types of intelligence is and even which one is ‘superior’. Would you rather have more fluid intelligence or more crystallized intelligence?

gaining intelligence

The answer of course is that neither is superior and that each has its uses. What’s more, is that it isn’t quite as clear cut a definition as you might expect.

One interesting thing to note though is that fluid intelligence tends to be better when we’re younger but then decline as we get older. Conversely though, crystallized intelligence is something that improves as you age. The older you get, the more time you have to experience things, to read books and to collect knowledge.

Something to consider here though is that the distinction isn’t perfect. For one, someone with better fluid intelligence might find it easier to learn more things. They might also feel more motivated to discover new subjects. In this way then, there is a strong correlation between the two types of intelligence meaning that they aren’t entirely separate.

Where do Differences Come From?

Of course, fluid intelligence itself can be broken down into many other different types of intelligence. Psychologists like Gardner posit that we have multiple ‘types’ of intelligence which could all be considered fluid, whereas modular theories of the brain point to the different roles that different brain areas have when it comes to planning, memorizing and using language.

One big predictor of fluid intelligence though is working memory. The working memory is a little like the brain’s ‘RAM’; it is what allows it to store information temporarily for use during thinking. If you need to perform mental arithmetic for example, then you will likely need to ‘carry over’ numbers in your mind while you perform sums and multiplications. This is handled by the working memory.

Likewise, the working memory allows us to store images in our mind’s eye (called the ‘visospatial scratch-pad’) and to remember names and phone numbers (using the ‘phonological loop’). It is also closely correlated with attention and our ability to stay fixated on a certain subject. 

It’s only with repetition and when we view information as being important that it goes on to be transferred to the short term memory and then later the long-term memory for permanent storage. And it is at this point that it begins to contribute to overall ‘crystallized intelligence’. The long term memories seem to be stored by the limbic system and in particular, by the hippocampus. The limbic system is also in charge of many of our emotions however and thus it might be that it encourages the storage of information that it views as emotionally ‘important’.

Abstract Thinking

intelligence is fluid

But to say that fluid intelligence is entirely the result of working memory and attention would be a mistake. It is true that the working memory enhances our ability to focus, to make quick decisions and to juggle information, but it is less involved in the kind of creative thinking that gives rise to novel ideas.

Actually, creativity appears to be the result of having a more relaxed approach to thinking. The general view is that new ideas are only ever created by combining old ideas in unique ways. If you can do this, then you can ‘think outside the box’ and you can come up with new inventions, stories and creations.

In order to have these kinds of creative thoughts though, it is important to be able to let the mind ‘wander’, which in turn appears to be closely linked to emotion, as well as to overall connectivity throughout the brain.

What’s also true though, is that by having more knowledge, you might actually be better able to recombine that information in new ways. The more ‘input’ you have, the more ‘output’ you will be capable of.


We would describe all these types of intelligence as ‘fluid’. The ability to focus on a task, excellence in a particular area (such as math) or the ability to come up with novel ideas. The mechanisms behind these types of thinking are many and not fully understood but by categorizing them as ‘fluid’, we can at least make the distinction between knowledge and information.

So, what can you do to improve these types of intelligence? What should you do with this information?

One tip is to practice training your working memory if you want to increase your fluid intelligence and to spend some time relaxing and letting your mind wander if you want to come up with new ideas.

And through it all, keep on learning. Because not only will this help you to come up with new ideas and work in tandem with your fluid intelligence, but it is also the type of intelligence that will stay with you long into old age!