Children have more interaction with unfamiliar adults. They acquire the aggressive language needed to defend their toys in the playground that show they know the difference between how adults talk to babies and how they talk to each other. These can be observed in pretend play using different voices. Other than, they begin to understand how and why language varies and then the children also develop metalinguistic awareness that is the ability to treat language as an object separate from the meaning it conveys. They may show that they know it's a bit odd, but they will focus mainly on the fact that they can understand what it means. Five years old on the other hand know that is wrong in a different way from they can tell you but the other is the wrong way around.