Intelligence (the kind that’s measured on an IQ test) is one kind of human ability. Its importance sometimes gets overinflated, but other times, it seems to get framed as a negative thing. So, how much does intelligence actually matter?
Intelligence and IQ tests
There are all kinds of different human abilities. The psychological construct of intelligence is one kind of ability that’s measured by intelligence quotient (IQ) tests. There’s more detail in a previous post I did on IQ, but according to David Wechsler, who developed the Wechsler Adult Intelligence Scale (WAIS), intelligence is “the global capacity of a person to act purposefully, to think rationally, and to deal effectively with his environment” (as quoted in Wikipedia).
The WAIS, currently in its 4th edition (WAIS-IV), has four subscales:
- Verbal comprehension
- Perceptual reasoning
- Working memory
- Processing speed
It’s scored on a bell curve rather than the raw score you get on a test. It’s normed so that the median score is 100, and 68% of people fall within a range of 100 plus or minus 15 (statistically, one standard deviation).
The concept of emotional intelligence has also been proposed, but from what I’ve read, it hasn’t been as clearly established that it’s a single distinct thing rather than a mishmash of other things. For example, some aspects of what’s captured under the emotional intelligence umbrella may relate to levels of different personality traits like extraversion and neuroticism.
Crystallized vs. fluid intelligence
Psychologist Raymond Cattell formulated the Gf-Gc theory of intelligence. He believed that intelligence (G) came from the coordination of fluid intelligence (Gf) and crystallized intelligence (Gc). Fluid intelligence is the general, untaught ability to understand relationships between elements of an abstract problem, and then use that to solve the problem. Crystallized intelligence comes from knowledge accumulated through experience, and it’s more specific in terms of its usefulness for particular kinds of problems.
Both fluid and crystallized intelligence increase through childhood. In early adulthood, Gf (including processing speed) starts to decline, while Gc stays the same or even increases. Gc can be influenced by experience, but also by factors like interest and motivation.
In a paper on the relationship between general knowledge and intelligence, the researchers concluded that general knowledge is a crystallized ability that comes from applying fluid intelligence over time. However, while intelligence was a factor in people’s level of knowledge, it wasn’t the only one. Personality factors, like higher levels of openness to experience and lower levels of neuroticism and extraversion, were also associated with higher levels of general knowledge, so having a high level of general knowledge doesn’t necessarily mean that someone is highly intelligent.
What intelligence means for school & work
IQ is a strong predictor of early academic success, but it becomes less relevant in higher levels of education. This may relate to the fact that people who’ve made it into higher education are likely to have had a higher IQ to begin with. It may also have to do with crystallized intelligence starting to play a bigger role at that stage of the game.
In terms of job success, the relevance of IQ depends on how complex the job is and the level of intellectual/reasoning demands.
Routine IQ testing
I don’t actually have an idea how widespread routine IQ testing in schools is. It wasn’t a thing when I was going to school.
I haven’t done any reading on whether there are good reasons for routine testing, but it doesn’t strike me as something that would be particularly useful. Intelligence can be a helpful ability to have, but you can’t magic it in or out of existence, so if schools know a kid’s IQ, what are they doing with that information? Unless they’re using it in some way to support all kids to do better, I’m not sure how it’s helping anyone to have those scores.
Aside from that, there are various reasons why an IQ test score may not accurately reflect an individual’s intelligence. Let’s say someone who speaks a particular nonstandard English dialect takes the WAIS-IV IQ test. Scores are based on group norms, and the normative data for a given test is probably based on standard dialect speakers. That test taker’s score on the verbal comprehension scale may not end up representing their actual abilities, because the scoring is making an apples to oranges comparison.
IQ and Health
IQ is correlated with health outcomes and longevity, and this seems to relate to the ability to make use of available information and resources in order to address health-related issues and make decisions about health-related behaviours. Socioeconomic status plays a major role in health, but even within a given socioeconomic group, health differences are observed between individuals of higher and lower intelligence.
However, IQ may also have negative associations with certain health conditions. A study of Mensa members (who are at or above the 98th percentile on IQ tests) found higher than average rates of allergies, asthma, autoimmune conditions, mood disorders, ADHD, and autism spectrum disorder. The researchers proposed a theory to account for this that they described as hyper brain/hyper body.
While research results have been somewhat mixed, childhood intelligence doesn’t appear to play a big role in the risk for dementia in older age. Lifestyle and environmental factors appear to be much more important. It’s possible that higher baseline intelligence might initially mask the early stages of cognitive decline.
The bigger picture
Setting aside the potential flaws of IQ tests, whether someone has high or low intelligence in the IQ sense can give you some information about certain things they may or may not be good at, but it doesn’t tell you whether someone is a good person, what their other abilities may or may not be, or what their personality traits are.
Having high intelligence doesn’t make someone an arrogant ass who’s useless with people; those are distinct elements that can sometimes be present in the same person, but not necessarily. Having low intelligence doesn’t make someone a useless human; there are all kinds of tasks for which other abilities are far more important, and intelligence has no bearing on whether those other abilities are or are not present. Intelligence is just one of the many pieces that make up the bigger picture of an individual.
What are your thoughts on intelligence, what it means, and what it matters for?
- Chamorro-Premuzic, T. (2007). Personality and individual differences. Blackwell Publishing.
- Chamorro-Premuzic, T., Furnham, A., & Ackerman, P. L. (2006). Ability and personality correlates of general knowledge. Personality and Individual Differences, 41(3), 419-429.
- Ghisletta, P., & Lecerf, T. (2018). Crystallized and fluid intelligence. Oxford Bibliographies.
- Karpinski, R. I., Kolb, A. M. K., Tetreault, N. A., & Borowski, T. B. (2018). High intelligence: A risk factor for psychological and physiological overexcitabilities. Intelligence, 66, 8-23.
- Rodriguez, F. S., & Lachmann, T. (2020). Systematic review on the impact of intelligence on cognitive decline and dementia risk. Frontiers in Psychiatry, 11, 658.