Piaget’s Conservation Task A five-year-old compares the liquid in the two short beakers, then watches as liquid is poured into a tall, narrow beaker. When asked which has more, the girl insists that there is more liquid in the tall beaker. As Piaget’s classic task demonstrates, the average 5-year-old doesn’t grasp this principle of conservation.

(all) Bianca Moscatelli/Worth Publishers