The concept of conservation refers to the understanding that certain properties of an object (such as its quantity, length, or volume) remain the same even when its physical appearance changes. It is a key cognitive milestone in child development.
A Swiss psychologist known for his theory of cognitive development which includes stages such as preoperational stage where children struggle with conservation.
The stage in Piaget's theory during which children gain the ability to think logically about concrete objects and perform mental operations but still struggle with abstract or hypothetical concepts.