Psychologist Jean Piaget showed children two identical glasses filled with the same amount of water. After the children agreed that both glasses held the same amount of water, Piaget poured the water from one glass into a taller, narrower glass and then asked them about the amounts of water in each glass. Tyler thought that the taller glass held more water because the water line was higher than in the shorter, wider glass. This is an indication that Tyler is in the __________ stage of development.