Technically, you can increase IQ by being healthy, doing intellectually engaging activities, and waiting a long time.
This is because IQ is relative, and fluid intelligence goes down as time goes by, but the above activities maintain your cognitive capabilities for longer, so if you do them you’ll be smarter relative to other people your age, which is what higher IQ is.
They speak about developing cognitive reserve in Alzheimer’s disease context.
I was wondering if there are people that actually acquire higher fluid intelligence over time in absolute terms, and if so, if we can learn something by studying them. Chatting with LLMs, they mention the Seattle Longitudinal Study, where some people do increase some aspects of fluid intelligence until about 50 years old, predicted by 5 factors:
They have “High Occupational Complexity”
They possess a “Flexible” Personality Style
The “Smart Spouse” Effect
Pristine Cardiovascular Health
They Develop “Cognitive Dedifferentiation”
This is a nice break from “no intervention ever works”, though note that I have not checked any of this information beyond chatting with LLMs, so this may turn out wrong.
I didn’t expect this to get this many downvotes / disagreements. If there are factual mistakes, it would be useful to know where exactly. For reference here’s what a “fact check that” prompt turns out in Gemini 3.1 Pro. It points out factor 5 is wrong, it is a negative factor. But everything else passes the check.
Gemini 3.1 Pro fact checking
Here is a fact-check of the claims you brought up. The LLM you chatted with provided a surprisingly accurate summary of cognitive aging research, but it completely misunderstood and hallucinated the final point about “Cognitive Dedifferentiation.”
Here is the breakdown of the facts:
1. IQ relativity, fluid intelligence, and “waiting” to increase IQ
Status: True IQ is an age-normed (relative) metric. Your score is based on how well you perform compared to other people your exact age. Because fluid intelligence (the ability to reason, solve novel problems, and think abstractly) naturally peaks and then declines as people age, the “average” baseline for older age brackets drops. If you manage to stall your own cognitive decline through a healthy lifestyle and intellectual engagement, your raw cognitive abilities might stay the same, but your IQ score will technically go up because your performance is now being compared to a lower average.
2. Cognitive Reserve in the context of Alzheimer’s
Status: True The concept of “Cognitive Reserve” was heavily popularized by neuroscientist Dr. Yaakov Stern specifically in the context of aging and Alzheimer’s disease. It explains the phenomenon where some people’s brains show severe Alzheimer’s pathology during an autopsy, yet they displayed no outward symptoms of dementia while alive. A lifetime of education, complex occupations, and mental stimulation builds a “reserve” that allows the brain to functionally compensate for physical damage [1, 2, 7].
3. Seattle Longitudinal Study (SLS): Fluid intelligence increasing until age 50
Status: True The Seattle Longitudinal Study (directed by K. Warner Schaie starting in 1956) is arguably the most important study on adult cognitive development [6, 7]. Before the SLS, cross-sectional studies suggested that human intelligence peaked in our early 20s and steadily dropped. However, the SLS tracked the same individuals over decades and proved that several primary mental abilities—including aspects of fluid intelligence like inductive reasoning and spatial orientation—actually increase through early adulthood and peak in middle age (typically late 30s to early 50s) [7, 8, 9]. Significant cognitive decline for most people doesn’t begin until after age 60 [7].
4. The 5 Predictors of Cognitive Maintenance/Increase
Status: 4 are True, 1 is False (LLM Hallucination)
The SLS explicitly identified specific variables that predict who maintains or improves their cognitive abilities and resists decline. The LLM was right about four of them, but completely wrong about the fifth [1, 3]:
High Occupational Complexity (True): Involvement in a complex, intellectually stimulating environment (often mediated by high socioeconomic status and complex work) forces the brain to adapt and maintains cognitive function [1, 3].
Flexible Personality Style (True): Schaie found that having a “flexible” (as opposed to rigid) personality style at midlife is a major predictor of retaining intelligence in old age [1, 3]. People who adapt well to change fare better cognitively.
The “Smart Spouse” Effect (True): This is one of the most famous findings of the SLS. The study explicitly lists “high cognitive status of spouse” as a protective factor [1, 3]. Over time, married couples’ cognitive trajectories tend to converge. If you are married to someone highly intelligent and cognitively active, it acts as a buffer against your own cognitive decline [1, 3].
Pristine Cardiovascular Health (True): The “absence of cardiovascular and other chronic diseases” is a primary baseline for maintaining intelligence [1, 3]. What is good for the heart is good for the brain.
They Develop “Cognitive Dedifferentiation” (FALSE): The LLM made a severe error here. “Cognitive dedifferentiation” is a real term studied within the SLS, but it is a negative phenomenon. As humans age and approach the end of life, their distinct cognitive abilities (like memory, spatial reasoning, and verbal fluency) become highly correlated with one another, losing their distinct “differentiation” [10, 11]. Dedifferentiation is a sign of terminal cognitive decline and aging, not a protective factor [11, 12, 13].
What the 5th factor actually was: If you look at K. Warner Schaie’s official list of protective factors from the SLS, the factor the AI missed was actually “Maintenance of high levels of perceptual processing speed.” [1, 3] Those who actively keep their mental processing speed quick (often through training or engaging activities) are the ones who retain their fluid intelligence the longest [1, 3].
Summary: Your underlying premise is solidly backed by developmental psychology. You absolutely can “hack” your age-adjusted IQ by protecting your brain so that it outpaces the normative decline of your peers. Just don’t try to “develop cognitive dedifferentiation”—that is an AI hallucination of a term that actually means the exact opposite!