Jul 14, 2026·Improving IQ / Preparation7 Everyday Ways You Are Ruining Your IQ
Are your daily routines suppressing your intelligence? Discover the 7 common habits quietly lowering your cognitive ability. Read the guide and take the RIOT test!
Dr. Russell T. WarneChief Scientist
Intelligence isn't as fixed as most people assume. While your genetic baseline sets a range, your daily environment and habits determine where within that range or how far below it your cognitive performance actually lands. The research on cognitive suppression is now detailed enough that I can be specific about which behaviors move the needle, how much, and through which mechanisms. None of the seven habits below is dramatic. That's precisely what makes them dangerous. They are ordinary, normalized, and collectively capable of pulling your measured cognitive performance several IQ points below where it would otherwise sit.
1. Chronic Sleep Restriction
This is the highest-leverage item on the list and the one most consistently underestimated. Most adults think of sleep as a lifestyle variable, something adjustable based on workload. The research treats it as a cognitive maintenance system, and what happens when you skip it is measurable.
A large randomized study of 182 participants found that one night of total sleep deprivation produced measurable impairments across attention, arithmetic ability, episodic memory, and working memory — all domains directly assessed by professional IQ batteries. A longitudinal study of medical students documented that sleep-deprived students showed significant reductions in tonic alertness, selective and sustained attention, and cognitive inhibition. The cognitive domains hit hardest — attention, working memory, and executive function — are exactly the ones most heavily weighted in modern assessments. What makes this habit particularly insidious is that research shows just 6 hours of sleep affects your brain like being legally drunk — and chronic mild restriction compounds across days in ways that feel normal because the impairment accumulates gradually. Unlike total sleep deprivation, which is subjectively terrible, chronic mild restriction produces cognitive impairment that the person doesn't reliably feel. You adapt to feeling slightly worse and call it your baseline. It isn't.
2. Passive Scrolling and Attention Fragmentation
The relationship between habitual short-form content consumption and cognitive performance is one of the more clearly emerging findings in the recent literature on Gen Z cognitive decline — which I covered in depth in a separate article in this series.
The mechanism is specific: passive scrolling trains your brain to operate in short bursts of attention, rewarding rapid context-switching and penalizing sustained engagement. The problem is that the cognitive operations most important for reasoning — working memory, sustained attention, deliberate analysis — depend on the ability to hold a problem in focus across time. That capacity atrophies with disuse.
A 2025 study found that TikTok required less cognitive effort than any other platform tested — less than Instagram Reels, less than YouTube Shorts — by precisely calibrating its content delivery to prevent the development of sustained attentional focus. This isn't accidental. It's a design feature. And the research on digital technology and cognition is consistent: heavy screen exposure is linked to lower gray matter volume in key decision-making areas of the prefrontal cortex. The brain region most responsible for the kind of structured thinking that IQ tests assess is the one shrinking in response to the modern information diet.
3. A Diet High in Sugar and Processed Foods
This one has more biological precision behind it than the standard "eat healthy" advice implies. The mechanism isn't vague nutritional wisdom — it's specific neuroendocrine disruption.
A diet high in sugar, refined carbs, and processed foods has been shown to impact cognitive health by increasing inflammation and even shrinking key brain regions like the hippocampus. The hippocampus is the brain region most directly responsible for memory consolidation and spatial navigation — and it is also the region most sensitive to dietary inflammation and insulin dysregulation. Chronically elevated blood glucose damages the hippocampus through multiple pathways: oxidative stress, neuroinflammation, impaired BDNF production, and disrupted synaptic plasticity. The short-term effect is the blood sugar crash: a rapid spike in glucose followed by a sharp decline that impairs working memory and processing speed for hours. The longer-term effect is structural. Studies have linked junk food-heavy diets to lower academic performance, slower mental processing, and measurable reduction in the brain regions most relevant to learning. This isn't about occasional indulgence. It's about dietary patterns that become the brain's baseline operating environment.
4. Chronic Stress Without Management
Stress is the most biologically precise cognitive suppressor on this list, and it operates through a mechanism that the neuroscience literature has now documented with considerable specificity.
Persistent elevation of cortisol — the primary stress hormone — is associated with reduced hippocampal volume, impaired neurogenesis, and disruptions to synaptic plasticity. A systematic review synthesizing evidence from 25 peer-reviewed studies confirmed all three effects. The hippocampus has a high density of glucocorticoid receptors, making it especially sensitive to sustained cortisol elevation. In patients with Cushing Syndrome — a disorder of chronically elevated cortisol — the most frequent cognitive symptoms reported are impaired memory (83%) and shortened attention span (66%). The prefrontal cortex is the second major target. The prefrontal cortex — the region responsible for working memory, attention, cognitive flexibility, and impulse control — is significantly affected by chronic stress, with chronic cortisol dysregulation associated with structural alterations in stress-sensitive regions. The domains the prefrontal cortex governs are exactly the ones IQ batteries are most directly designed to measure. Unmanaged chronic stress is, in effect, a biological attack on the neural substrate of measured intelligence.
5. Sedentary Behavior
Most people know that exercise is good for the brain. Fewer realize that sitting is actively bad for it, independent of whether you exercise at other times of day.
A UCLA study found that long sitting hours correlate with thinner brain regions related to memory. The mechanism is reduced cerebral blood flow: the brain is metabolically expensive and depends on continuous oxygen and glucose delivery through the circulatory system. Sustained sitting suppresses blood flow in ways that exercise later in the day does not fully compensate for, particularly in the medial temporal lobe — the network most critical for memory formation. The exercise-IQ relationship is well-documented and I covered it in depth in the exercise article in this series. The point here is slightly different: the absence of movement is itself a suppressor, not just the absence of formal exercise. Research shows that moving every 45 minutes, even briefly, supports brain health in ways that a single morning workout cannot substitute for. The brain was not designed to operate for eight consecutive hours without the circulation benefits that even light movement produces.
6. Outsourcing Thinking to Technology
This is the newest item on this list in terms of the research literature, and the one whose long-term consequences are least fully understood — but the early data is consistent enough to warrant inclusion.
A 2025 study found that use of large language models like ChatGPT leads users to consistently overestimate their cognitive performance regardless of actual ability or AI literacy. More substantively, the mechanism proposed is that AI tool use reduces the metacognitive reflection that normally occurs during effortful cognitive work. When AI handles a reasoning task, the user doesn't generate the internal feedback loop that calibrates both self-knowledge and cognitive skill. The broader principle has older evidence behind it. When someone habitually avoids deep thinking by outsourcing it — to GPS instead of navigation, to AI instead of writing, to calculators instead of estimation — they are systematically reducing the practice of the cognitive operations that IQ tests assess. Skill in reasoning, like skill in anything, declines with disuse. The brain does not maintain capacities it isn't required to exercise. Using technology as a substitute for thinking rather than a tool to amplify it is the distinction that matters here — and it's one most people are not making deliberately.
7. Social and Intellectual Isolation
The research on social engagement and cognitive performance is consistent enough to belong on this list, even though it's the least discussed of the seven.
When someone avoids new ideas, deep conversations, or challenging tasks, they engage their cognitive abilities less — and over years, that avoidance becomes self-reinforcing. Cognitively demanding social interaction — debate, collaborative problem-solving, teaching, complex conversation — exercises working memory, perspective-taking, language processing, and executive function simultaneously in ways that passive media consumption does not. These are the same capacities IQ batteries assess. The longitudinal evidence on this is particularly striking in older populations, where social isolation is associated with accelerated cognitive decline at rates that exceed what biological aging alone would predict. But the mechanism operates across all age groups: social and intellectual isolation reduces the frequency of cognitively demanding experiences, which reduces the stimulation that drives neuroplasticity and maintains the neural circuits underlying performance. This is not an argument for socializing more in general — passive social media consumption, despite being technically social, likely falls on the wrong side of this distinction. The relevant variable is cognitively demanding engagement: interactions and activities that require you to generate, evaluate, and communicate ideas under conditions of genuine uncertainty.
The Common Thread
Seven habits, one underlying mechanism: each of these behaviors suppresses either the brain's physical infrastructure — through cortisol damage, inflammation, or reduced blood flow — or the regular practice of the cognitive operations that keep that infrastructure functional. None of them feel like intellectual decline in the moment. That's exactly what makes them consequential.
The practical implication is also consistent across all seven: measured IQ on any given day reflects genuine cognitive capacity minus whatever these suppressors have taken away. Removing them doesn't create new intelligence — it returns performance closer to your actual potential. That gap between suppressed performance and genuine capacity is, for many people, meaningful — and worth recovering.
If you want to know where your cognitive performance sits right now — across processing speed, working memory, fluid reasoning, and verbal comprehension — the RIOT gives you a domain-level profile that makes the current state of each index visible, rather than leaving you to estimate it.
References
PubMed Central. (2021). Quantifying Cognitive Impairment After Sleep Deprivation at Different Times of Day. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8076531/ PubMed Central. (2021). Sleep deprivation effects on basic cognitive processes: attention, working memory, and executive functions. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8340886/ TechXplore. (2025). AI use makes us overestimate our cognitive performance, study reveals. https://techxplore.com/news/2025-10-ai-overestimate-cognitive-reveals.html PubMed Central. (2024). Effects of chronic stress on cognitive function — From neurobiology to intervention. https://pmc.ncbi.nlm.nih.gov/articles/PMC11407068/
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AuthorDr. Russell T. WarneChief Scientist
