Fluid Intelligence: Definition, Examples, & Psychology

By Kelsey Schultz, Ph.D. Candidate
​Reviewed by Tchiki Davis, M.A., Ph.D.
Scientific research suggests that there are different kinds of intelligence. Keep reading to learn about one of the most essential types: fluid intelligence.​
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What does it mean to be intelligent? Intelligence is one of those things that we can recognize when we see it but is nevertheless very difficult to define. We might feel that someone is intelligent if they are good at trivia or problem-solving. A person who gets good grades or has a good memory might be considered intelligent. However, none of these attributes alone comprise a comprehensive definition of intelligence.​
Psychologists and cognitive neuroscientists have grappled with this challenge for over a century and are in consistent debate even today over how to define and measure intelligence. Despite disagreements about the specifics, most scientists agree that the concept of intelligence should include two factors: fluid intelligence and crystallized intelligence. Both fluid and crystallized intelligence are important components, but fluid intelligence is the general cognitive ability that most of us are referring to when we describe someone as smart. Let’s talk more about what fluid intelligence is and what science has to say about it.
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What Is Fluid Intelligence? (A Definition)​

Fluid intelligence refers to the capacity of an individual to think and reason flexibly, solve new and unfamiliar problems, and adapt to novel situations (Horn & Cattell, 1967). This generalized mental ability includes cognitive processes such as:
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  • Abstract thinking: Fluid intelligence involves the ability to grasp concepts that might not have any direct real-world representation. This includes understanding symbolism, metaphors, and other abstract ideas.
  • Reasoning: Fluid intelligence includes the capacity to analyze and make logical deductions, even when dealing with unfamiliar information.
  • Problem-solving: Fluid intelligence helps in quickly identifying patterns and relationships within information, which is crucial for solving complex problems.
  • Adaptability: Individuals with higher fluid intelligence are better at adapting to new and changing situations. They can apply their cognitive skills to a variety of tasks and contexts.
  • Working memory: Fluid intelligence often relies on working memory, which is the ability to hold and manipulate information in one's mind for short periods.

Benefits of Fluid Intelligence​

It would be hard to oversell the benefits of fluid intelligence. Because it is the basis of a variety of cognitive capabilities, like learning and problem-solving, fluid intelligence offers several benefits. Some of the key benefits of fluid intelligence include:
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  • The ability to analyze new information and adapt your thinking and behavior to your context
  • Solving complex problems such as those that arise in the fields of science, engineering, and mathematics
  • Learning new skills and grasping new concepts
  • Creativity
  • Critical thinking
  • The ability to flexibly shift your perspective
  • Decision making
  • Innovation

Examples of Fluid Intelligence

Examples of fluid intelligence can be observed in many aspects of our daily lives. Changing tactics when a project fails, navigating a challenging conversation, and deciding how best to structure our day are all examples of fluid intelligence. More obvious examples can be found in the tests that are designed to measure fluid intelligence. Here are a few of the cognitive tasks that require fluid intelligence (Fry & Hale, 2000; Kent, 2017):
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  • Pattern recognition: Identifying patterns within a series of abstract shapes, numbers, or symbols is a classic example of fluid intelligence. For instance, recognizing the underlying rule in a sequence of shapes and predicting the next shape requires the ability to discern patterns.
  • Analogical reasoning: Solving analogies, such as "A is to B as C is to ___," requires the ability to find relationships between different pairs of items and apply that relationship to another pair. This reflects the capacity to think abstractly and make connections.
  • Matrix reasoning: Matrix puzzles involve completing a grid of patterns by identifying the missing piece that fits the pattern established by the other elements. This task tests the ability to recognize relationships and predict outcomes.
  • Raven's Progressive Matrices: This is a widely used test that measures abstract reasoning. Participants are presented with visual patterns and must choose the option that completes the pattern based on the established rules.
  • Mental rotation: Mental rotation tasks involve mentally manipulating two-dimensional or three-dimensional objects and determining if they are the same or different when rotated. This assesses spatial visualization and cognitive flexibility.
  • Spatial reasoning: Tasks that involve understanding spatial relationships, such as navigating through a maze, assembling puzzles, or visualizing how different objects fit together, demonstrate fluid intelligence.

Fluid Intelligence vs. Crystallized Intelligence

Fluid intelligence and crystallized intelligence are both important aspects of cognitive functioning. The difference in these two types of intelligence was initially proposed by psychologist Raymond Cattell in the 1940s based on a research method called factor analysis. The details of factor analysis are a little too complicated to go into here (and probably would not make for a particularly exciting read). In essence, it is a mathematical technique that allows researchers to peer into how different variables interact with each other and contribute to the observed outcome. Since these two factors of intelligence were proposed, neuroscientific research has provided ample support for the theory (Kent, 2017).

The basic distinction between fluid and crystallized intelligence is that crystallized intelligence is the knowledge that we accumulate over our lifetimes, and fluid intelligence is the ability to use that knowledge to problem solve and use logic and reason. Below are some other important differences between the two concepts.

​The nature of fluid and crystallized intelligence differs. Fluid intelligence is more closely associated with innate cognitive abilities and is less influenced by education and culture. It's often considered more "raw" cognitive power. On the other hand, crystallized intelligence is heavily influenced by education, culture, and personal experiences. It reflects the knowledge we gain and the skills we accumulate throughout our lives.

The developmental trajectory is different between fluid and crystallized intelligence. Fluid intelligence peaks in early adulthood and gradually declines as a person ages. This type of intelligence is more vulnerable to the effects of aging and neurological changes. Crystallized intelligence continues to develop and increase over a person's lifespan as they acquire more knowledge and experiences and is less affected by age-related declines.

Fluid intelligence plays a different role in learning than crystallized intelligence. As mentioned previously, fluid intelligence is an essential part of developing new skills, adapting to new environments, and grasping new or complex concepts. In fact, these abilities are part of the definition of fluid intelligence. We use our crystallized intelligence to provide a context in which to situate the new information we receive. In other words, we need crystallized intelligence to build on what we have learned previously.​

Fluid Intelligence in Psychology

Scientific investigations of intelligence began in the late 19th century. These investigations were spearheaded by Sir Francis Galton and Charles Spearman, who believed that there was a general intellectual ability that was the basis of all mental activity (Kent, 2017).

In the early 20th century, methods for measuring intelligence proliferated among psychological researchers. These tests were not built on an explicit theory of intelligence, were inconsistent in how they defined intelligence, and lacked evidence of reliability and validity (Kent, 2017). However, throughout the development of many of these tests, the basic understanding that there was a general intelligence factor that influenced all other aspects of intelligence persisted.

The general intelligence hypothesis was challenged in 1941 by Raymond Cattell, who proposed that intelligence actually consisted of two factors: fluid and crystallized intelligence. Cattell and his colleague, John Horn, conceptualized fluid intelligence as an innate, biologically based phenomenon that involves the capacity to think flexibly, learn, reason, and perceive complex relationships (Kent, 2017).

Models of fluid intelligence and its relationship to other mental faculties are still being refined. However, the concept of fluid intelligence and methods developed for measuring it have proven to be useful in our current understanding of intelligence (Kent, 2017). For example, fluid intelligence has been investigated as an important factor in science learning (Yuan et al., 2006) and creativity (Silvia & Beaty, 2012).

Fluid Intelligence and Age​

The relationship between fluid intelligence and age is complex and dynamic. Research has shown that fluid intelligence tends to increase throughout childhood and adolescence and peaks during early adulthood (Fry & Hale, 2000). Similar to other cognitive abilities such as memory and attention, fluid intelligence tends to decline with increasing age (Bugg et al., 2006).

Fluid Intelligence Jobs

People with high fluid intelligence tend to excel in tasks that involve problem-solving, abstract thinking, and adapting to new situations quickly. They are often adept at learning and applying new information, making connections between disparate concepts, and finding innovative solutions to complex challenges. Here are some job roles that are well suited for individuals with high fluid intelligence:
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  • Research scientist: Fluid thinkers are skilled at designing experiments, analyzing data, and generating novel hypotheses. Whether in fields like physics, biology, psychology, or social sciences, research scientists need to think critically and creatively to advance knowledge.
  • Data scientist/analyst: Analyzing complex data sets, identifying trends, and extracting valuable insights all require strong problem-solving and analytical skills. Data scientists use their fluid intelligence to tackle various business challenges.
  • Software developer/engineer: Developing software applications or writing code involves logical thinking, problem-solving, and creativity. Fluid thinkers can excel at designing innovative software solutions.
  • UX/UI designer: Creating user-friendly and visually appealing interfaces demands an understanding of human behavior, empathy, and creative problem-solving—qualities often found in individuals with high fluid intelligence.
  • Management consultant: Fluid intelligence allows consultants to quickly grasp complex business problems, identify areas for improvement, and provide strategic recommendations to clients.
  • Entrepreneur: Starting and running a business requires adapting to changing circumstances, solving problems, and finding new opportunities—all skills associated with high fluid intelligence.
  • Investment analyst/trader: Fluid thinkers can excel in analyzing market trends, assessing risk, and making informed investment decisions in the fast-paced world of finance.
  • Neuroscientist: The study of the brain's intricate functions and complexities requires the ability to grasp abstract concepts and devise innovative experiments, making it a suitable field for individuals with high fluid intelligence.
  • Architect/industrial designer: Designing functional and aesthetically pleasing structures or products involves merging creativity with logical problem-solving.
  • Mathematician: Fluid thinkers often have a knack for understanding complex mathematical concepts and formulating new theories or proofs.
  • Strategic planner: Developing long-term strategies, anticipating future trends, and adapting plans to changing circumstances are tasks that play to the strengths of those with high fluid intelligence.
  • Air traffic controller: Managing and coordinating the movement of aircraft in busy airspace requires quick decision-making, multitasking, and the ability to adapt to rapidly changing situations.
  • Emergency room physician: High fluid intelligence is valuable in fast-paced medical environments where doctors must quickly diagnose and treat patients based on a wide range of symptoms and data.
  • Psychologist/psychiatrist: Understanding complex human behaviors, diagnosing mental health conditions, and developing tailored treatment plans all require a strong blend of analytical and empathetic thinking.
  • Innovation manager: Facilitating innovation within an organization involves identifying opportunities for improvement, brainstorming new ideas, and developing strategies to implement them.

Fluid Intelligence and ADHD

Fluid intelligence is closely linked with a cognitive function known as working memory (Unsworth et al., 2014). Working memory is essentially the ability to temporarily hold information in your mind. For example, you need working memory to do things like making decisions or performing mental math.

One of the primary deficits in attention-deficit/hyperactivity disorder (ADHD) is working memory capacity. In other words, people with ADHD tend to have a harder time holding bits of information for short periods of time. The relationships between working memory and fluid intelligence and between working memory and ADHD suggest that ADHD could be associated with decreases in fluid intelligence (Cornoldi et al., 2013).

Current research shows that, despite the relationships between working memory, fluid intelligence, and ADHD, people with ADHD do not necessarily exhibit lower fluid intelligence than people without ADHD (Cornoldi et al., 2013).

Articles Related to Fluid Intelligence

​Want to learn more? Check out these articles:

Books Related to Fluid Intelligence

If you’d like to keep learning more, here are a few books that you might be interested in.

Final Thoughts on Fluid Intelligence​

Fluid intelligence refers to the ability to think flexibly, use logic and reason, understand complex relationships, and solve problems. This kind of intelligence is critical for learning new skills and adapting to new environments. Fluid intelligence typically increases throughout childhood and adolescence, peaks in early adulthood, and then declines with increasing age. For more on fluid intelligence, check out this video:​

Video: Fluid Intelligence Across the Lifespan: Brains and Behaviour​

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