Every part of any language can be dived into discrete, learnable units of meaning, with the smallest unit being the phoneme.  These units exist to accomplish communicative goals.  The realization that language has components that serve functions provides a starting point for teaching.  To what extent these units are dependent upon nature or nurture is not as relevant to the language learner as is the fact that because these units have been ill-defined, their full potential in language teaching has not been realized.

The most basic units of meaning are phonetic.  These are sounds attached to meaning, such as the /s/ sound, the /f/ sound, and so on.  As with later, more complex languge parts, early parts are learned to assist a person in communicating words and concepts with those parts.  A child that can not make the /s/ sound is likely to be frustrated when communicating any idea with any word containing the /s/ sound.  This provides a natural impetus for the child:  learn that sound or continue to be frustrated each time an /s/ is required.