Hierarchical structure for the Wechsler variables. The numbers in circles are the standardized loadings of the cognitive ability factors on the higher-order common factor in an initial analysis in which age was partialled from each variable. The other numbers are standardized coefficients for the linear age relations on the constructs. Gc refers to crystallized ability, Gf to fluid ability, WM to working memory, VbM to verbal memory, ViM to visual memory, and Spd to speed. All coefficients are significantly different from zero (p < .01).