Raw IQ changes systematically across the human lifespan at the group level
Intelligence and cognitive abilities change systematically across the human lifespan, showing distinct developmental peaks and aging trajectories for fluid versus crystallized domains.
The claim is specific and empirically verifiable, testing whether intelligence or raw IQ changes systematically across the human lifespan. Retrieved papers such as [9] and [10] provide direct, high-quality lifespan developmental and longitudinal evidence showing clear, systematic trajectories (such as the rise and fall of fluid and crystallized intelligence and memory across adulthood). There is no refuting evidence among the papers.
Anna M. Momy, Daniel Baena, Laura B. Ray, Adrian Owen, Stuart M. Fogel. Are Age‐Related Differences in Sleep Associated With the Different Trajectories of Fluid and Crystallized Intelligence Across the Lifespan?. 2026. https://doi.org/10.1111/jsr.70364
Paper 9 details how fluid and crystallized intelligence exhibit distinct, systematic trajectories across the lifespan, with fluid intelligence peaking in early adulthood and declining thereafter while crystallized intelligence behaves differently.
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Georgette Argiris, Yaakov Stern, Christian Habeck. Nonlinear Lifespan Trajectories of Memory and Fluid Reasoning: A Longitudinal GAMM Study. 2025. https://doi.org/10.21203/rs.3.rs-8313556/v1
Paper 10 uses longitudinal modeling to demonstrate robust, systematic nonlinear age-related changes and declines in cognitive domains such as memory and fluid reasoning across adulthood.
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