What does volume is a conservative dimension mean in the context? Does conservative have to do with the verb conserve in meaning?
During their second year, children learn to use the words old and young, which indicate that they have appropriated the age dimension. They can use this dimension to classify people. However, an understanding of an abstract time domain develops much later. Spatial metaphors for time are ubiquitous: it is difficult to talk about time without using words that originate from the visuospatial domain. Jean Piaget emphasizes that “time and space form an inseparable whole” in children’s minds. In other words, young children cannot treat space and time as separate domains. This situation parallels the dimensions of height and volume, which are inseparable for preschool children but become separable when children learn that volume is a conservative dimension. Similarly, space and time start as a single metric that becomes gradually differentiated into two separable domains.