What ability allows individuals to understand that the amount of a substance remains unchanged despite changes in form, developed later in childhood?

The concept of conservation is crucial in child development, as it refers to the understanding that certain properties of objects remain constant despite changes in their form or appearance. For example, children who have developed conservation can recognize that pouring water from a short, wide glass into a tall, narrow glass does not change the actual amount of water present, even though it may look different due to the change in shape.

This ability typically emerges during the concrete operational stage of cognitive development, according to Jean Piaget, usually between the ages of 7 and 11. The skill of conservation reflects cognitive advances, as children begin to think logically about physical transformations and understand that certain attributes (like volume, mass, or number) are invariant to change.

Transformation, while related, refers more to the change that occurs in an object or substance rather than the understanding that some characteristics remain the same. Reversibility involves the idea that actions can be reversed to return to the original state, which supports the understanding of conservation but is a separate, distinct concept. Class inclusion refers to the understanding of hierarchies in categories or classes, which is different from understanding conservation. Thus, conservation is the correct answer as it directly addresses the understanding of quantity remaining unchanged despite changes in form.