In which stage of cognitive development does the concept of conservation first emerge?

The concept of conservation first emerges in the concrete operational stage of cognitive development, which occurs approximately between the ages of 7 and 11 years, according to Jean Piaget's theory. During this stage, children begin to understand that certain properties of objects, such as volume, mass, and number, remain the same despite changes in their form or arrangement. For instance, they can realize that pouring water from a short, wide glass into a tall, narrow one does not change the amount of water, demonstrating an understanding of conservation.

In the preoperational stage, which precedes concrete operational thinking, children generally lack this understanding and may believe that the quantity of a substance changes with its appearance. In the sensorimotor stage, which occurs from birth to about 2 years, children focus on their immediate sensory experiences and motor actions and do not yet engage in logical thought processes. The formal operational stage, beginning around age 12, involves more abstract reasoning and problem-solving skills but does not play a role in the initial emergence of conservation. Thus, the concrete operational stage is critical for the development of this important cognitive ability.