Knowledge
complete guides
In-depth long-form guides to IQ, the IQ scale, percentiles, the history of psychometric testing. Come here when you want to understand a topic thoroughly.
Fluid vs Crystallized Intelligence — what's the difference
Intelligence is not singular. Raymond Cattell distinguished two fundamental types: fluid (solving new problems) and crystallized (accumulated knowledge). Each behaves differently over time.
The IQ Scale — what does a score of 100, 115, 130, or 145 mean?
The IQ scale is not just a number — it's a map of how cognitive abilities are distributed across the population. We explain what scores of 100, 115, and 130 actually mean, where you stand relative to others, and where this scale even came from.
What is IQ? A Complete Guide to the Intelligence Quotient
IQ is one of the most studied and most misunderstood numbers in psychology. This guide explains what it really measures, where it comes from, and what it cannot tell you.