Four-year-old Jonathan is sitting at the lunch counter next to his sister Erin. They are having hot dogs for lunch. When his mom cuts Jonathan's hot dog into five pieces and Erin's into six pieces, Jonathan protests, "Erin has more than me!" Which ability does Jonathan not yet demonstrate?

Conservation

Explanation:

Conservation: The term is defined in the Piaget's child developmental theory in the concrete operational stage and is based on rational or logical thinking. This concept states that different things stay in the same position even when other related elements change. The age in which conservation occurs is between seven to eleven.

According to Piaget, by conservation, a child understands that by changing the shape of any object or substance will not change its volume, mass, or amount.

So, as per the question, Jonathan doesn't demonstrate the conservation ability because of his age.