Fluid Versus Crystallized Intelligence: What’s the Difference?

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The theory of fluid and crystallized intelligence proposes that there are two distinct kinds of intelligence. Fluid intelligence refers to the ability to reason and solve problems in unique and novel situations, while crystallized intelligence refers to the ability to use knowledge acquired through past learning or experience.

The theory was first proposed by psychologist Raymond B. Cattell and developed further with John Horn.

Fluid vs. Crystallized Intelligence

  • The theory contends that there are two distinct types of intelligence. It challenges, and extends, the concept of g, or generalized intelligence factor.
  • Fluid intelligence is the ability to use logic and solve problems in new or novel situations without reference to pre-existing knowledge.
  • Crystallized intelligence is the ability to use knowledge that was previously acquired through education and experience.
  • Fluid intelligence declines with age, while crystallized intelligence is maintained or improved.

Origin of the Theory

The theory of fluid intelligence challenges the idea of generalized intelligence factor (known as g), which contends that intelligence is a single construct. Instead, Cattell contended that there are two independent intelligence factors: “fluid” or gf intelligence, and "crystallized” or gc intelligence.

As he explained in his 1987 book Intelligence: Its Structure, Growth, and Action, Cattell referred to the ability to reason as fluid intelligence because it “has the ‘fluid' quality of being directable to almost any problem.” He referred to knowledge acquisition as crystalized intelligence because it “is invested in the particular areas of crystallized skills which can be upset individually without affecting the others.”

Fluid Intelligence

Fluid intelligence refers to the ability to reason, analyze, and solve problems. When we use fluid intelligence, we aren’t relying on any pre-existing knowledge. Instead, we are using logic, pattern recognition, and abstract thinking to solve new problems.

We use fluid intelligence when we encounter novel, often nonverbal tasks, such as math problems and puzzles. Fluid intelligence also plays a role in the creative process, as when someone picks up a paintbrush or starts plucking on a piano with no prior training.

Fluid intelligence is rooted in physiological functioning. As a result, these abilities start to decline as people age, sometimes starting as early as their 20s.

Crystallized Intelligence

Crystallized intelligence refers to the knowledge you acquire through experience and education. When you use crystallized intelligence, you reference your pre-existing knowledge: facts, skills, and information you learned in school or from past experience.

You utilize crystallized intelligence when you encounter tasks that require the use of previously acquired knowledge, including verbal tests in subjects like reading comprehension or grammar. Given its reliance on the accumulation of knowledge, crystallized intelligence is typically maintained or even increased throughout one's lifetime.

How the Intelligence Types Work Together

Although fluid and crystallized intelligence represent two distinct sets of abilities, they can and often do work together. For example, when cooking a meal, you use crystallized intelligence to understand and follow the instructions in a recipe, and use fluid intelligence when modifying spices and other ingredients to suit your tastes or dietary requirements. Similarly, when taking a math test, the formulas and math knowledge (like the meaning of a plus sign) comes from crystallized intelligence. The ability to develop a strategy to complete a complicated problem, on the other hand, is the product of fluid intelligence.

Fluid intelligence is often used when learning new things. When you encounter a new subject, you use your fluid intelligence to understand the material through logical and analysis. Once you understand the material, the information will be incorporated into your long-term memory, where it can develop into crystallized knowledge.

Can Fluid Intelligence Be Improved?

While crystalized intelligence improves or remains stable with age, fluid intelligence is known to decline fairly rapidly after adolescence. Several studies have investigated whether it is possible to improve fluid intelligence.

In 2008, psychologist Susanne M. Jaeggi and her colleagues conducted experiments in which four groups of young, healthy participants performed a highly demanding working memory (short-term memory) task every day. The groups performed the task for 8, 12, 17, or 19 days respectively. The researchers found that participants’ fluid intelligence improved following the training, and that the more training participants underwent, the more their fluid intelligence improved. Their study concluded that fluid intelligence can, in fact, improve through training.

Another study using a similar protocol backed up Jaeggi’s results, but subsequent studies have not replicated the findings, so the results of Jaeggi’s study are still considered controversial.


  • Cattell, Raymond B. Intelligence: Its Structure, Growth, and Action. Elsevier Science Publishers, 1987.
  • Cherry, Kendra. “Fluid Intelligence vs. Crystallized Intelligence” Verywell Mind, 2018. https://www.verywellmind.com/fluid-intelligence-vs-crystallized-intelligence-2795004
  • Chooi, Weng-Tink, and Lee A. Thompson. “Working Memory Training Does Not Improve Intelligence in Healthy Young Adults.” Intelligence, vol. 40, no. 6, 2012, pp. 531-542. 
  • Dixon, Roger A., et al. “Cognitive Development in Adulthood and Aging.” Handbook of Psychology, vol. 6: Developmental Psychology, edited by Richard M. Lerner, et al., John Wiley & Sons, Inc., 2013.
  • Jaeggi, Susanne M., et al. “Improving Fluid Intelligence with Training on Working Memory.” Proceedings of the National Academy of Sciences of the United States of America, vol. 105, no. 19, 2008, pp.6829-6833, 
  • Qiu, Feiyue, et al. “Study on Improving Fluid Intelligence Through Cognitive Training System Based on Gabor Stimulus.” Proceedings of the 2009 First IEEE International Conference on Information Science and Engineering, IEEE Computer Society, Washington, DC, 2009. https://ieeexplore.ieee.org/document/5454984/
  • Redick, Thomas S., et al. “No Evidence of Intelligence Improvement After Working Memory Training: A Randomized, Placebo-Controlled Study.” Journal of Experimental Psychology: General, vol. 142, no. 2, 2013, pp. 359-379, http://psycnet.apa.org/doiLanding?doi=10.1037%2Fa0029082
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Vinney, Cynthia. "Fluid Versus Crystallized Intelligence: What’s the Difference?" ThoughtCo, Dec. 6, 2021, thoughtco.com/fluid-crystallized-intelligence-4172807. Vinney, Cynthia. (2021, December 6). Fluid Versus Crystallized Intelligence: What’s the Difference? Retrieved from https://www.thoughtco.com/fluid-crystallized-intelligence-4172807 Vinney, Cynthia. "Fluid Versus Crystallized Intelligence: What’s the Difference?" ThoughtCo. https://www.thoughtco.com/fluid-crystallized-intelligence-4172807 (accessed February 8, 2023).