There are a few different theories as to why and how children develop language. One popular, yet heavily debated explanation is that language is acquired through imitation. This theory has been challenged by Lester Butler, who argues that children do not use the grammar that an adult would use. Furthermore, "children's language is highly resistant to alteration by adult intervention", meaning that children do not use the corrections given to them by an adult. R.L Trask also argues in his book "Language: The Basics" that deaf children acquire, develop and learn sign language in the same way hearing children do, so if a deaf child's parents are fluent sign speakers, and communicate with the baby through sign language, the baby will learn fluent sign language. And if a child's parents aren't fluent, the child will still learn to speak fluent sign language. Trask's theory therefore is that children learn language by acquiring and experimenting with grammatical patterns, the statistical language acquisition theory.