Final answer:
In Piaget's theory of cognitive development, the preoperational stage occurs from around 2 to 7 years old. In this stage, children can use symbols, engage in pretend play, and make judgments based on personal knowledge. However, they have difficulty with reversible operations and mental operations.
Step-by-step explanation:
In Piaget's theory of cognitive development, the preoperational stage is the second stage, which typically occurs from around 2 to 7 years old. In this stage, children can use symbols to represent words, images, and ideas, and engage in pretend play. However, they have difficulty understanding the concept of reversible operations and perform mental operations. They also make judgments based on personal knowledge rather than conventional knowledge.