Is a Gifted IQ Score Reliable? The Math Says 1 in 4 Won't Repeat
A gifted IQ score of 130 feels like a verdict, yet the reliability math expects more than 1 in 4 one-shot labels to regress below the line on a retest.
IQ Science
IQ Science
The science of intelligence: g-factor research, fluid vs crystallized intelligence, Flynn effect, and psychometric methodology explained.
Does IQ Predict Job Performance? A Shrinking Number
Cognitive ability still predicts job performance, but the corrected correlation fell from r = .51 in 1998 to r = .22 in 2024. See what shrank and what held up.
The Best Age to Peak by Profession: A Cognitive-Gap Table
There is no single peak age. See how 10 professions map onto the abilities that peak at 19, 25, or the late 60s, and why experience offsets raw-speed decline.
Working Memory Is the Ceiling: Why Deliberate Practice has Limits in Adult Careers
Why working memory caps expert performance, what the deliberate-practice meta-analyses show, and what to train when more reps stop working. The science.
Does IQ Decline With Age? A Decade-by-Decade Cognitive Trajectory
Decade-by-decade IQ data from Hartshorne, Salthouse, Schaie, and Singh-Manoux shows no single peak age. See which abilities decline, hold, or rise after 45.
How Average IQ Varies Across 200+ Countries: What the Data Actually Shows
National IQ averages vary dramatically, but the data is more contested than most sources admit. Here's what the science shows, and what it means for you.
What Is Cognitive Intelligence? The Science Behind Your Brain's Most Powerful Career Asset
Cognitive intelligence predicts job performance better than any other trait. Learn the science behind g-factor, fluid vs. crystallized IQ, and career impact in 2026.
13 Cognitive Biases That Lower Your Effective IQ: What the Research Shows
Intelligence doesn't protect against cognitive biases. Research shows some get worse with higher IQ. See 13 biases with their measured decision costs.