In which developmental stage do children start to understand conservation according to Piaget?

The understanding of conservation occurs during the concrete operational stage, which typically spans from ages 7 to 11 years. In this stage, children begin to think logically about concrete events and develop the ability to understand that certain properties of objects, such as volume, mass, and number, remain the same even when their form or appearance changes. For instance, a child in this stage can understand that pouring water from a short, wide glass into a tall, narrow glass does not change the amount of water, demonstrating their grasp of conservation.

This ability marks a significant cognitive advancement from the previous preoperational stage, where children are often led by appearances and may mistakenly believe that the taller glass contains more water. The concrete operational stage is characterized by logical thinking about tangible and observable phenomena, differentiating it from earlier stages where such cognitive awareness is not yet developed.