sentences:  Studies of language variation and its correlation with sociological categories, such as William Labov's 1963 paper "The social motivation of a sound change," led to the foundation of sociolinguistics as a subfield of linguistics.Although contemporary sociolinguistics includes other topics, language variation and change remains an important issue at the heart of the field.Studies in the field of sociolinguistics typically take a sample population and interview them, assessing the realisation of certain sociolinguistic variables.