We examined the factor structure of the intelligence and basic skills domains of the Intelligence and Development Scales–2 (IDS-2) and measurement invariance across the Dutch and German versions, sex, and age with confirmatory factor analyses and local structural equation modeling of the standardization samples. Of several theoretically and empirically determined models, a second-order model with six first-order factors best represented the Dutch IDS-2 structure. Five IDS-2 factors were confirmed, but Visual Processing and Abstract Reasoning and the intelligence and basic skills domains were not separable. This final model displayed full invariance across the Dutch and German versions and partial scalar invariance across sex, and it appeared largely invariant across ages 7 to 20 years. The strong general intelligence factor and weak broad ability factors suggest individual interpretation should mainly be based on the full-scale IQ. We discuss the importance of testing multiple plausible models and implications for theory and practice.

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