Final answer:
The child who responds "Bow-wow!" to the sound in "dog" is in the preoperational stage of development, as characterized by the use of symbols and lack of understanding of conservation and logic operations.
Step-by-step explanation:
The child who responds with "Bow-wow!" when asked about the first sound in the word "dog" is exhibiting a behavior associated with Piaget's preoperational stage of cognitive development. This stage typically occurs from approximately 2 to 7 years of age. During the preoperational stage, children are able to use symbols to represent objects and engage in pretend play, but they do not yet have the ability to perform certain mental operations such as understanding conservation.
For instance, in the provided example about the pizza being cut into different numbers of slices, a child in the preoperational stage like Kenny may believe he has more pizza because it is divided into more pieces, showing a lack of conservation understanding. This is primarily because their thinking is centered and not yet capable of logical operations which include understanding that quantity remains the same despite changes in the form or appearance of objects.