For decades, intelligence tests have measured general knowledge by asking questions based on traditional academic subjects. Recent research has revealed that information learned through personal life experience and information learned in the classroom are actually driven by the very same underlying mental abilities. The study, published in the journal Intelligence, suggests that human knowledge is a deeply unifying property, regardless of the environment in which it is acquired.
Human intelligence has traditionally been divided by psychologists into two broad conceptual categories. Fluid intelligence describes the active ability to solve new problems, adapt to unfamiliar situations, and recognize underlying patterns without relying on previous experience. Crystallized intelligence, on the other hand, refers to the vast accumulation of facts, vocabulary, and practical skills collected over a person’s lifetime. As people age, fluid intelligence tends to slowly decline, while crystallized intelligence continues to grow as we experience more of the world.
Psychologists typically measure this accumulated knowledge through standardized intelligence tests. These assessments have historically focused on standard school curriculum subjects such as world history, mathematics, and classical literature. Many researchers consider this to be a very practical way to construct tests because educational curricula provide a reliable, standardized framework that people are generally expected to know.
Elisa Altgassen, a psychology researcher at the University of Ulm in Germany, led the new study along with Johanna Hartung from the University of Bonn. Researchers suspected that the reliance on traditional academic subjects ignored large parts of human experience. If tests measure only what people learn in the classroom, we risk underestimating the true breadth of human intelligence.
Because people continue learning long after they graduate from formal education, traditional tests may not capture the vast amount of information that adults gain through their hobbies, careers, and leisure travel. Rather than sitting at a desk and listening to a teacher, adults often obtain information in informal, unstructured ways.
In the world of cognitive psychology, researchers frequently debate how different types of knowledge are stored in the brain. Semantic memory is a functional system responsible for remembering general, context-independent facts, such as the knowledge that Paris is the capital of France. Episodic memory is associated with specific personal experiences, such as remembering a particular vacation to Paris.
Historically, psychologists have suspected that facts learned through personal real-world experience may be fundamentally different from facts memorized from a blackboard. Altgassen and his team wanted to find out whether everyday learning could be separated from formal education at a measurable psychological level. They also set out to investigate whether natural curiosity drives people to seek out specific life experiences that build worldly knowledge.
To explore these ideas, researchers designed an experiment involving 348 adults between the ages of 30 and 40. The researchers purposefully selected this particular age range to ensure that all participants enjoyed enough time to gather a variety of experiences in adult life, while preventing advanced cognitive aging from skewing the final test results. The research team also ensured that the participants had a balanced mix of educational backgrounds and were in line with the German Federal Statistical Office’s population quotas.
Each person completed a comprehensive online survey. The survey includes a standardized test of school-based knowledge, with 60 questions covering topics typically taught through the 10th grade in the standard education system.
The research team also developed an entirely new set of 66 questions designed to test knowledge acquired outside of formal education. This second test covered conceptual areas such as agriculture, modern technology, and art.
Participants then responded “yes” or “no” to a series of biographical questions. Each of these biographical questions was explicitly paired with a specific item on the Everyday Knowledge test.
For example, a knowledge test question asking to name a computer’s central processing unit was combined with a background question asking whether participants had ever physically disassembled a desktop computer. Another question asking about Barcelona’s famous architecture was combined with a question about whether the participant had ever visited that particular city.
Finally, participants completed a psychological questionnaire designed to measure their overall openness to new experiences and typical level of intellectual engagement. Intellectual engagement is a personality trait that determines how much a person enjoys thinking deeply and continually seeking out new information.
When the researchers analyzed the test results, they found that the scores for school knowledge and daily life knowledge were perfectly matched on a statistical level. The fundamental mathematical relationship between the two types of knowledge is incredibly strong, showing that there is no true separation between them.
This indicates that people who perform well on tests in classroom subjects are equally likely to possess a variety of random facts that they have acquired in their daily lives. The two categories of knowledge do not function as separate mental engines in the brain.
Instead, they reflect a single, unified ability to gather and recall information. The researchers concluded that learning ability is consistent across contexts, whether individuals are sitting in a lecture hall or watching an informative video online.
The study also found that a person’s general intellectual curiosity predicts performance on both types of tests equally well. Curious people tend to absorb more information overall and demonstrate a consistent drive to understand how the world works. Researchers initially expected curiosity to play a larger role in informal learning, under the assumption that academic environments force all students to digest specific information, regardless of their level of personal interest. Instead, the data showed that a natural desire for knowledge produced higher fact retention in both structured and unstructured environments.
However, when examining the data at the individual question level, individual experience made a huge difference. Psychologists study test results by looking at an individual’s general cognitive abilities, along with the unique statistical variance associated with the specific questions on the test. This unique difference helps researchers pinpoint why some people know the answer to one very specific question, but not another question of the same difficulty.
If the participants actually took apart the computer, they were much more likely to answer the computer hardware questions correctly, even after the researchers statistically adjusted for the participants’ overall intelligence level. The statistical associations between specific life events and corresponding knowledge test items were very strong.
An individual’s unique background is directly related to improved fact retention in a particular field. This suggests that while general intelligence is an integrated ability, the specific facts a person holds are largely determined by the actual activities in which the person participates. Exposure to targeted experiences is associated with a clear advantage in intelligence test questions related to those experiences.
The study authors noted several limitations to their study. First of all, it is inherently difficult to pinpoint exactly where an individual learned a particular fact.
Participants may have learned about the famous painting in middle school art class, or may have seen the painting featured on a television show last week. This mix of educational pathways means that the distinction between formal and informal learning is always approximate and rarely absolute.
The researchers also noted that they only surveyed a narrow age range of adults in Germany. Different populations may exhibit different learning patterns, depending largely on the educational infrastructure and cultural norms of each country. Furthermore, it is quite possible that lack of knowledge actively motivates people to seek new experiences, complicating the directional relationship between life events and learning.
In the future, the researchers hope to enable scientists to follow individuals over decades to see exactly when certain life events become retained as knowledge. The researchers ultimately hope to improve this type of psychological assessment to create more fair intelligence tests that better take into account the vastly different ways people learn about the world.
The study “From school lessons to life lessons: the relationship between school knowledge, life knowledge and biographical experience” was authored by Elisa Altgassen, Johanna Hartung, Diana Steger, Ulrich Schroeders and Oliver Wilhelm.
