At around what age do most children understand that the same amount of liquid can appear different when poured into different containers?

Most children begin to grasp the concept of conservation — understanding that the quantity or amount remains the same despite changes in shape or appearance — around the ages of 6 to 7. This developmental milestone reflects significant cognitive progress associated with Piaget's theory of cognitive development, particularly during the concrete operational stage.

At this age, children start to comprehend that if you pour liquid from a short, wide container into a tall, narrow one, the volume remains unchanged even as the liquid's appearance alters. Prior to this age, younger children may not recognize that the volume remains constant. They may believe that taller or narrower containers hold more liquid simply because they look different, indicating their ongoing development in logical reasoning and spatial awareness.

Understanding this concept is key, as it marks a shift towards more sophisticated cognitive skills, laying a foundation for later mathematical reasoning and understanding of quantity that children will build on as they grow.