The document summarizes studies conducted by two major linguists, William Labov and Peter Trudgill. It describes Labov's 1963 study on Martha's Vineyard where he analyzed pronunciation patterns related to vowel centralization among inhabitants. He found patterns varied by age, occupation, location and population group. The study was significant as it considered social factors in dialects, unlike previous research. It also summarizes Trudgill's study of final consonant pronunciation in Norwich, England, finding patterns varied by social class and gender. Both studies contributed to the development of sociolinguistics by illustrating how linguistic variations are associated with social factors.