Lack of Conservation: Children do not yet understand that certain properties (like quantity, volume, or mass) remain the same even when the appearance of an object changes. For example, they might think that a taller, narrower glass contains more water than a shorter, wider glass, even if they saw the same amount of water poured from one glass to the other. "applying logic" is a key step in this stage, as your notes suggest, but mastering this logic takes time.