developing Appalachian English and the Great Migration bringing African-American Vernacular English to the Great Lakes urban centers. Phonology Any phonologically unmarked North American accent is known as "General American" (akin to Received Pronunciation in British English, which has been referred to as "General British"). This section mostly refers to such General American features. Conservative phonology Studies on historical usage of English in both the United States and the United Kingdom suggest that spoken American English did not simply deviate away from period British English, but is conservative in some ways, preserving certain features contemporary British English has since lost. Full rhoticity (or R-fulness) is typical of American accents, pronouncing the phoneme (corresponding to the letter ) in all environments, including after vowels, such as in pearl, car and court. Non-rhotic American accents, those that do not pronounce except before a vowel, such as some Eastern New England, New York, a specific few (often older) Southern, and African American vernacular accents, are often quickly noticed by General American listeners and perceived to sound especially ethnic, regional or "old-fashioned". Rhoticity is common in most American accents, although it is now rare in England because during the 17th-century British colonization nearly all dialects of English were rhotic, and most North American English simply remained that way. The preservation of rhoticity in North America was also supported by continuing waves of rhotic-accented Scotch-Irish immigrants, most intensely during the 18th century (and moderately during the following two centuries) when the Scotch-Irish eventually made up one-seventh of the colonial population. Scotch-Irish settlers spread from Delaware and Pennsylvania throughout the larger Mid-Atlantic region, the inland regions of both the South and North and throughout the West: American dialect areas that were all uninfluenced by upper-class non-rhoticity and that consequently have remained consistently rhotic. The pronunciation of is a postalveolar approximant or retroflex approximant , but a unique "bunched tongue" variant of the approximant r sound is also associated with the United States, perhaps mostly in the Midwest and the South. American accents that have not undergone the cot–caught merger (the lexical sets and ) have instead retained a – split: a 17th-century distinction in which certain words (labeled as the lexical set) separated away from the set. The split, which has now reversed in most British English, simultaneously shifts this relatively recent set into a merger with the (caught) set. Having taken place prior to the unrounding