The document discusses Piaget's stages of child development, focusing on the concrete operational stage where children ages 7-11 can think more logically and rationally. It specifically examines the concept of conservation, where children understand that changing appearance or shape does not change quantity. The document describes a conservation task test to determine if a child has gained this conservation skill, providing an example of a 4-year-old girl named Mira who is unable to pass the test because at her preoperational stage, children lack the ability to recognize that changing appearance does not alter quantity.