IQ & Psychometrics Glossary

Cognitive domains are distinct areas of mental ability such as reasoning, memory, processing speed, and verbal comprehension.

Crystallized intelligence (Gc) is accumulated knowledge, vocabulary, and learned skills applied in familiar contexts.

Fluid intelligence (Gf) is the capacity to solve novel problems and detect patterns without relying on stored knowledge.

The general intelligence factor (g) is a statistical construct representing shared variance across diverse cognitive tasks.

An IQ score is a standardized index of cognitive performance relative to a norm group, typically scaled to mean 100.

Mensa is a high-IQ society that accepts members who score at or above the 98th percentile on approved supervised tests.

Norms are reference data from representative samples used to interpret raw scores as percentiles or standard scores.

A percentile ranks your score against a reference population — e.g., the 90th percentile means you scored higher than about 90% of the norm group.

Raven's Progressive Matrices (RPM) are non-verbal visual puzzles used to estimate fluid reasoning ability.

Reliability is the consistency of measurement — whether repeated testing yields similar results.

Standard deviation (SD) measures score spread around the mean; IQ tests commonly use SD 15 (Wechsler) or SD 16 (Stanford-Binet).

The Stanford-Binet Intelligence Scales are a major individually administered IQ battery spanning ages 2 to 85+.

Validity is the degree to which a test measures what it claims to measure.

The Wechsler Adult Intelligence Scale (WAIS) is a leading individually administered IQ battery for adults.

Working memory is the ability to hold and manipulate information briefly while performing a task.