One major difference between Piaget's cognitive development model and Schaie's model of cognitive development is
Piaget focused on the entire life span, while Schaie concentrated only on childhood and adolescence.
Schaie ignored childhood completely and Piaget focused only on childhood.
Schaie's models address cognitive development across the life span, while Piaget ended at adolescence.
Piaget's model ignored the first five years of cognitive development, while Schaie's model did not.