ABSTRACT
One of the central themes of many introductory psychology descriptions of intellectual development is to remind us (and our students) that young children are cognitively different and not simply small adults. The Piagetian concept of conservation (e.g., Piaget & Inhelder, 1969)—that volume or mass remains the same despite changes in shape, form, or distribution-provides some of the most dramatic demonstrations of such cognitive differences. For example, if you pour water from a short, wide glass into a narrow, tall one, a 5-year-old who has not mastered conservation of volume is likely to say that there is more water in the narrow glass “because it [the water level] is higher.” Similarly, when you roll one of two identical balls of clay into a sausage shape, the 5year-old who has not mastered conservation of mass is likely to say that there is now more clay in the latter “because it is longer.”
