At which cognitive development stage do children typically learn the concept of conservation?

Children typically learn the concept of conservation during the concrete operational stage. This stage, occurring roughly between the ages of 7 and 11, is marked by significant cognitive advancements. During this time, children begin 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, when shown two identical glasses of water, if one glass is poured into a taller, narrower glass, a child in the preoperational stage might think that the taller glass contains more water. However, once they reach the concrete operational stage, they can grasp that the amount of water is conserved regardless of the glass's shape. This new understanding signifies a shift from intuitive thinking to more logical reasoning, enabling children to engage in more complex cognitive tasks. Hence, this is the key reason why the concrete operational stage is the correct answer.