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. The two most accepted theories in language development are psychological and functional. Psychological explanations focus on the mental processes involved in childhood language learning. Functional explanations look at the social processes involved in learning the first language. Aspects Phonology involves the rules about the structure and sequence of speech sounds. Semantics consists of vocabulary and how concepts are expressed through words. Grammar involves two parts. The first, syntax, is the rules in which words are arranged into sentences. The second, morphology, is the use of grammatical markers (indicating tense, active or passive voice etc.). Pragmatics involves the rules for appropriate and effective communication. Pragmatics involves three skills: using language for greeting, demanding etc., changing language for talking differently depending on who it is you are talking to; following rules such as turn taking, staying on topic. Each component has its own appropriate developmental periods. Phonological development Babies can recognize their mother's voice from as early as few weeks old. It seems like they have a unique system that is designed to recognize speech sound. Furthermore, they can differentiate between certain speech sounds. A significant first milestone in phonetic development is the babbling stage (around the age of six months). This is the baby's way of practicing his control over that apparatus. Babbling is independent from the language. Deaf children for instance, babble the same way as hearing ones. As the baby grows older, the babbling increases in frequency and starts to sound more like words (around the age of twelve months). Although every child is an