Final answer:
The stage described in the question is Piaget's preoperational stage, where children use symbols and engage in pretend play. They cannot understand adult logic or perform mental operations.
Step-by-step explanation:
The stage described in the question is Piaget's second stage of development, called the preoperational stage. This stage occurs from approximately 2 to 7 years old and is characterized by children using symbols to represent objects and feelings. They engage in pretend play and begin to use language, but their logic is based on their personal knowledge rather than conventional knowledge. Children in this stage have not yet developed an understanding of conservation.