Phonological development is the acquisition of sounds in order to pronounce words. Child Language Acquisition begins at birth. The inner ear has the only bones in the whole body which are fully formed at birth, thus enabling the child to start recognising their mother's voice in the first day of living and also allowing the child to differentiate one language from another at such an early stage. The vocal tract is not fully developed at birth which, when compared to the formation of the inner ear, helps to biologically explain why it is that perception of sounds comes before the ability to produce sounds. Through 'vocal playing' (highlighted in the 5 pre-verbal stages below) children learn to control their vocal tract to produce sounds accurately. (REMEMBER: Each child differs, so the dates provided are a guideline).