What key feature occurs during the concrete operational stage in Piaget's theory?

During the concrete operational stage, which occurs roughly between the ages of 7 and 11, children develop the ability to understand the concept of conservation. This means they can recognize that certain properties of objects, such as volume, mass, and number, remain the same despite changes in shape or arrangement. For example, a child at this stage can understand that if you pour water from a short, wide glass into a tall, narrow glass, the amount of water remains the same even though it appears different. This ability reflects a more logical thought process, allowing children to think about tangible objects and events in a more organized and systematic way.

In contrast, the ability to think abstractly, which is characteristic of the formal operational stage, does not emerge until later. Similarly, symbolic thought is more prominent during the preoperational stage, and the use of reflexes to explore is characteristic of the sensory-motor stage. Therefore, understanding conservation is the hallmark feature of the concrete operational stage, illustrating a key cognitive advancement in children's developmental progression.