Fluid and crystallised: two kinds of intelligence

Solving a problem you've never seen and using what you already know are different abilities. Good tests keep them apart.

Psychologists have long told apart two broad kinds of intelligence. Fluid intelligence is the ability to reason through problems that are new to you: finding the rule in a pattern you’ve never seen. Crystallised intelligence is what you’ve built up: vocabulary, facts, ways of doing things.

Why the difference matters

The two develop differently. Fluid reasoning tends to peak in early adulthood; crystallised knowledge keeps growing for decades. A test that leans on vocabulary rewards reading and schooling; a test of figure matrices barely does.

That’s why reasoning tests rely so much on matrices, series and spatial items: they need little prior knowledge, so they say more about reasoning itself. Verbal items add something different, the ability to see how ideas relate, and are kept to a few, using everyday words.

How Quotient uses both

Three of Quotient’s four subtests are fluid: matrices, number series and spatial rotation. The verbal subtest leans on simple words and plain logic, so it still measures relating more than knowing. Your report shows all four separately, so a strong result in one doesn’t hide a weaker one in another.