Final answer:
Lauren is most likely in Piaget's preoperational stage, where she can use symbols to represent words, images, and ideas but cannot understand adult logic or mentally manipulate information.
Step-by-step explanation:
Based on Zach's observations, Lauren is most likely in Piaget's preoperational stage of cognitive development. This stage occurs from approximately 2 to 7 years old, and children in this stage can use symbols to represent words, images, and ideas. They engage in pretend play and begin to use language. However, they cannot understand adult logic or mentally manipulate information like in the concrete or formal operational stages.