ABSTRACT
Preadolescent children’s understanding of the logic of class and length relationships has received considerable attention since Piaget’s pioneering investigations (Inhelder & Piaget, 1964; Piaget, 1965; Piaget & Inhelder, 1967; Piaget, Inhelder & Szeminska, 1960). Piaget reports that children less than 7–8 years of age (approximately) are unable to solve problems requiring fundamental class-inclusion and length concepts. Older children solve them with little difficulty. He characterizes the younger children as preoperational, and the older as operational.
