The contribution of general intelligence to cognitive performance across the lifespan: A differentiation analysis of the wechsler tests.

Human cognitive abilities exhibit positive interrelationships that can be represented by a latent general intelligence factor (g). Differentiation hypotheses propose that there are systematic interindividual differences in the strength of g, specifically along the dimensions of ability level (ability differentiation) and age (age differentiation). Despite the potential implications for cognitive theory and assessment, the available evidence on the matter is inconclusive.

Why the use of segmented regression analysis to explore change in relations between variables is problematic: A simulation study.

Relations between variables can take different forms like linearity, piecewise linearity, or nonlinearity. Segmented regression analyses (SRA) are specialized statistical methods that detect breaks in the relationship between variables. They are commonly used in the social sciences for exploratory analyses.