What is it called when a child understands that an object's weight does not change even if its shape does?

The understanding that an object's weight remains constant even when its shape changes is referred to as conservation of weight. This concept falls under the broader principle of conservation in developmental psychology, which explains that children learn that some properties of objects remain the same despite changes in form or appearance.

For example, when a child realizes that a lump of clay maintains the same weight regardless of whether it is flattened or molded into a different shape, they are demonstrating this understanding. Mastering such conservation concepts is a significant milestone in cognitive development, showing that the child can consider both physical properties and changes in their perception.

This reasoning differentiates conservation of weight from related concepts. For instance, object permanence is the understanding that objects continue to exist even when they cannot be seen. Horizontal decalage refers to a child's ability to demonstrate conservation skills across different contexts, and accommodation is a cognitive process where existing knowledge is altered to integrate new information. Each of these terms denotes distinct aspects of cognitive development, whereas conservation of weight specifically addresses the understanding of the constancy of an object's weight despite changes in shape.