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.
IQ Science
IQ Science
The science of intelligence: g-factor research, fluid vs crystallized intelligence, Flynn effect, and psychometric methodology explained.
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.
Signs Your Child May Be Gifted: When to Consider IQ Testing
Research-backed signs of giftedness in children and when IQ testing makes sense. Assessment options, costs, and program placement.
The Bell Curve: Visualizing Intelligence Distribution in the US
How IQ scores distribute across the US population. Where you rank, what each standard deviation means, and career implications.
The $70,000 Ceiling: Where IQ Stops Predicting Income (And What Takes Over)
IQ predicts income only up to ~$70K, then plateaus. The top 1% of earners score lower than those just below. See the data.