learn about IQ testing

Free guides on intelligence testing, scoring methodology, and cognitive science.

what is IQ?

The history and meaning of the intelligence quotient, from Binet to modern testing.

What each IQ range means, with percentiles, classifications, and rarity statistics.

Two types of cognitive ability, how they change with age, and why matrix tests measure one over the other.

The gold standard culture-fair IQ test, created in 1936 and still used worldwide.

The math behind the number: normal distributions, z-scores, percentiles, and the Flynn effect.

Enter any IQ score and instantly see your percentile rank, classification, and bell curve position.

Mensa requirements, accepted tests, how to join, and what the test is actually like.

How IQ varies by age and population, the Flynn effect, and why cross-country comparisons are misleading.

Twin studies, heritability estimates, environmental factors, and why nature vs nurture is the wrong framing.

What makes a good test vs a bad one, and how to evaluate whether your score means anything.