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Sleep, exercise, diet, illness, medication and environment — what each one measurably does to thinking, and by how much.
Large longitudinal studies find verbal memory scores dip, on average, during the menopause transition — then recover for most women afterward. Online discussion of "menopause brain fog" usually keeps only the first half of that finding.
The Lancet Commission ranks hearing loss as the largest single modifiable risk factor for dementia in midlife. It is also the most under-recognised way to depress a score on a test that is read aloud — two different problems that are easy to confuse.
Research presented at a European neuroscience meeting in July 2026 used magnetic brain recordings to estimate biological brain age, and found multilingual speakers scoring years below their calendar age. The gradient is striking. The design cannot show that languages caused it.
Processing speed peaks in your twenties. Vocabulary and knowledge keep climbing into your sixties. A synthesis published in Intelligence puts overall psychological functioning at its highest between 55 and 60 — and your IQ score cannot tell you where you sit on any of those curves.
Caffeine reliably lifts alertness, vigilance and reaction time, most of all in people who are tired. Evidence that it improves reasoning in rested, habitual drinkers is far weaker — and a disputed but substantial share of what it appears to add is a deficit the absence of the last cup created.
Almost every eleven-year-old in Scotland sat the same test on the same day in 1932. Decades later those scores turned out to track survival — and the argument about what that means has run ever since.
A bad night does not lower intelligence. It reliably lowers the things a timed test happens to measure most closely — sustained attention, working memory and speed — while leaving vocabulary and general knowledge comparatively intact.
An IQ figure is meaningless without the scale it was measured on and the range around it. Every story here reports all three, or says plainly that the source did not.
Each story ends with the studies, datasets and documents it draws on, named and attributed, so you can go and read them yourself.
Spotted an error? Write to corrections@iqmetrics.org. Corrections are made on the story and noted at the bottom of it — never quietly.
Our IIF-certified assessment reports your score with its scale, percentile and confidence range — and a breakdown of the cognitive domains behind it.
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