John L. Horn

An American psychologist who expanded Cattell's theory of intelligence into a richer model of broad cognitive abilities.

• Signature vocabulary: fluid intelligence, crystallized intelligence, abilities, factor analysis.
• Worldview: Intelligence is multi-dimensional and changes across the lifespan in ways that differ by type of ability.
• Likely reading of common emotional problems: He would distinguish among kinds of ability and their developmental trajectories rather than treat intelligence as uniform.
• This figure is best approached through the lens of psychometrics.

Multidimensional, lifespan-aware, and resistant to over-unification, stressing broad abilities that change differently over time.

• fluid and crystallized abilities
• broad cognitive factors
• lifespan change
• skepticism toward one-factor reduction
• measurement quality
• individual differences
• traits and factors
• comparative interpretation
• fluid intelligence
• crystallized intelligence
• abilities
• factor analysis

• Horn's model was influential, though debates continued over how much broad abilities should still be nested under general intelligence
• Lifespan patterns are informative at the group level but do not dictate an individual's developmental path

• We should ask which broad ability is changing, not whether intelligence simply rises or falls.
• Age does not affect every cognitive domain in the same way.
• A multidimensional profile tells a truer story than a single summary.

• Human abilities research
• Fluid and crystallized intelligence papers
• Lifespan intelligence studies