Final answer:
The child who uses symbols and language but lacks logical reasoning skills, as described in the question, is in Piaget's Preoperational stage of cognitive development.
Step-by-step explanation:
The child described in the question is in the Preoperational stage of Piaget's stages of cognitive development. This stage typically occurs from approximately 2 to 7 years of age. During this time, children are able to use symbols and language but are still unable to perform operations, which are mental tasks related to logic. An example provided is confusion about quantity conservation due to the child's focus on the appearance rather than the actual amount, like when Kenny thought he had more pizza because it was cut into more pieces. The preoperational stage is characterized by intuitive reasoning rather than logical or deductive thinking.