What Are Fluid And Crystallized Intelligence?

Crystallized intelligence and fluid intelligence were first defined in a landmark 1968 paper published in Psychological Review by cognitive psychologist John L. Horn, a pioneer in developing theories of intelligence.

Fluid intelligence generally refers to problem-solving skills, while crystallized intelligence can be thought of as a person’s accumulated knowledge. It is important to note that the word "intelligent" is not necessarily synonymous with "smart" or other positive descriptions of a person's mental aptitude. It is possible to continue improving your crystallized knowledge throughout your lifetime, and an online therapist can help you do so.

What is crystallized intelligence?

In simple terms, crystallized intelligence refers to accumulated or stored knowledge. The phrase "long-term memory" is often associated with crystallized intelligence, and although the two are not necessarily synonymous, they are considered similar concepts.

Knowledge acquired through experience and education

In educational psychology, crystallized intelligence generally refers to the accumulated knowledge a person can retain. When psychologists and researchers speak about crystallized intelligence, they are usually referring to a person's ability to apply previously acquired knowledge, skills, or prior learning to a problem in front of them. 

Crystallized intelligence is basically a person's encyclopedia. It can represent the bundled knowledge gained over the years, including everything from advanced concepts taught in school to basic knowledge like "birds have feathers." Because people can continue to learn throughout their entire lives, crystallized intelligence tends to increase the longer a person has been alive.

When people solve a problem using crystallized intelligence, they “look up” facts and information related to the problem in their “personal encyclopedia.” As an example, consider a doctor who specializes in a particular disease. After years of treating that disease, the doctor is likely to rely more on their own intuition than on medical texts and resources. They may have transferred the knowledge of that disease from medical literature to their personal encyclopedia, likely increasing their crystallized intelligence.

Crystallized intelligence vs fluid intelligence

Another type of intelligence is fluid intelligence, which refers to problem-solving and the ability to adapt to new situations. While the two concepts of intelligence are different, they can interact and work together.

Two core concepts of intelligence

Fluid intelligence, which is distinct from crystallized intelligence, typically involves a person's ability to solve new and unfamiliar problems. 

Unlike crystallized intelligence, which usually improves steadily over time, fluid intelligence typically peaks in early adulthood, around age 20. In general, fluid reasoning capacity slowly declines throughout adulthood, mainly due to age-related changes in the brain.

Fluid intelligence and crystallized intelligence are nearly always used together, as many tasks require fluid intelligence and cognitive flexibility as well as stored knowledge.

Examples in everyday life

Each of these types of intelligence can be used in daily life, either individually or together.

Fluid intelligence is used to solve problems on the fly. Possible examples include: 

• Figuring out a detour when your normal route is blocked
• Thinking and responding quickly during an argument
• Putting together a piece of flat-pack furniture

Crystallized intelligence requires using prior knowledge from past experiences, such as: 

• Recalling historical events
• Remembering geographical locations
• Cooking a meal without using a recipe

There are also situations in which you might use a combination of crystallized and fluid intelligence, including: 

• Using your own life experiences to parent while considering your child’s unique personality
• Learning to play a new instrument while drawing on your knowledge of a different instrument
• Using previous travel experience to navigate flights to a place you’ve never been
• Playing chess using strategies you’ve memorized while adapting to your partner’s moves on the boardiStock/insta_photos

How crystallized intelligence is measured

Measuring crystallized intelligence involves assessing all of the knowledge that a person has accumulated over their lifetime, including both education and life experience. While fluid intelligence measurements would assess problem-solving ability, crystallized intelligence testing looks at what someone has acquired over their lifetime, making it a relatively stable factor to measure.

Intelligence tests and assessment tools

The most commonly used standardized test to measure crystallized intelligence is the Wechsler Adult Intelligence Scale, which assesses intellectual abilities across four areas: verbal comprehension, perceptual reasoning, working memory, and processing speed. It is designed to measure knowledge rather than problem-solving skills. Other tools that may be used are the Cattell Culture Fair Intelligence Test and the Woodcock-Johnson Tests of Cognitive Abilities, and more generally, vocabulary scales can be an indication of a person's ability to define words and use language precisely, which reflects years of reading, learning, and communication.

Common test tasks and skills

Tests used to assess crystallized intelligence typically use concept formation tasks, like asking individuals to identify categories that are based on learned understanding, and logic puzzles that test how someone applies structured thinking. The matrix reasoning test, though often used to assess fluid intelligence, can overlap with crystallized intelligence when patterns are drawn on concepts learned over time.

Brain function and crystallized intelligence

Understanding crystallized intelligence can mean understanding the brain itself. Neuroscience has examined how long-term memory and stored knowledge are maintained and retrieved, revealing how the brain physically organizes the things we learn.

Cognitive neuroscience perspective

In human neuroscience, crystallized intelligence is associated with specific parts of the brain, such as regions involved in semantic memory, language processing, and long-term knowledge storage. Brain function in these regions supports the retrieval of encoded knowledge so that people can access stored knowledge quickly. The more connected mental representations of information are, the more effectively crystallized intelligence can operate.

Working memory and long-term knowledge

Working memory is the brain’s ability to hold onto and recall information in the short term. It can act as a gateway or precursor to processing information and eventually consolidating it into long-term storage. Strong cognitive function can help these experiences become part of crystallized memory. However, because crystallized knowledge depends more on the accumulation of learning over a lifetime, working memory training can be more beneficial for improving fluid intelligence and has less of an impact on crystallized intelligence.

Developmental trends across the lifespan

Crystallized intelligence builds gradually throughout the lifespan. Unlike many of our cognitive skills, crystallized intelligence increases with age.

Childhood, adulthood, and aging

Developmental trends in crystallized intelligence start early, as a child’s ability to absorb knowledge, including language and facts, lays the groundwork for future learning. In childhood, crystallized intelligence may be primarily driven by education and social interactions, while adult crystallized intelligence is generally due to accumulated knowledge and experience deepening, enriching ideas, frameworks, and vocabulary. Even in older adulthood, crystallized intelligence generally holds steady, but it can also grow. This is in contrast to fluid intelligence, which typically begins to decline in early adulthood.

When crystallized intelligence peaks

Research has found that crystallized intelligence typically peaks in the 60s, but that it may decline in older decades. This is in contrast to fluid intelligence, which peaks in early adulthood and then declines progressively with age. Because crystallized intelligence is cumulative in nature, every year spent engaging with the world, working, reading, or problem-solving adds to it. Processing speed and memory may fade with age, but stored knowledge can continue to expand as long as a person remains mentally engaged with the world around them.

Cultural and environmental influences

Crystallized intelligence is deeply shaped by the environment a person is raised in and how they engage with the world later in life.

Education, culture, and experience

Cultural background and environmental influences can play a significant role in shaping a person’s accumulated knowledge. An influential 2017 OECD education working papers report on ageing and skills stated, “Crystallized intelligence comprises…knowledge, skills and wisdom, abilities that are acquired or learned, and that are primarily socially and culturally determined.” Culture can have an impact on what knowledge is shared and valued; in other words, crystallized intelligence generally reflects the environment that built it.

Crystallized intelligence in real-world skills

Crystallized intelligence can show up regularly in everyday life and have an impact on personal growth and even professional or academic performance, as explored below. 

Problem-solving and strategy

Some of the clearest demonstrations of crystallized intelligence in everyday life may be in solving puzzles and strategy games, as these tasks can require analysis-synthesis reasoning skills, a core component of complex reasoning that consists of breaking down the complex parts of a problem and then putting them back together. 

Careers and lifelong learning

Many professions can benefit from high crystallized intelligence because it represents a substantial body of domain-specific skills acquired over time. Fields like engineering, law, medicine, and teaching allow individuals to draw on an already extensive body of knowledge while refining that knowledge in the acquisition of new skills. 

How crystallized intelligence supports mental health and resilience

The benefits of crystallized intelligence can go beyond learning and professional performance. The accumulated knowledge gained from everyday experiences can also play a meaningful role in navigating the challenges of everyday life.

Wisdom, perspective, and coping

Many scientific practitioner perspectives align with the idea that crystallized intelligence can support emotional regulation and help people develop a stronger sense of self. 

Drawing on past experiences can help people approach challenges from a different perspective. When people have faced challenges, survived them, and grown from them, they may be equipped to approach new obstacles with a proven set of tools. This capacity for reasoning and perspective shifting can act as an integrative measure of both intelligence and maturity, connecting knowledge to emotional response.

Getting support for cognitive growth

Investing in cognitive development can help improve resilience, decision-making, and overall well-being. Online therapy can help you find the confidence you need to achieve your crystallized intelligence goals, such as learning a new language or tackling complex tasks. As intelligence refers in part to the ability to retain and apply information, improving intelligence usually requires not only retention skills but also motivation and confidence. 

Completing therapy sessions online in the pursuit of improving intelligence can be convenient, and with online therapy, there is generally no need to leave home or seek out a therapist in your local area. Research has found that online therapy can be just as effective as traditional in-office therapy.