California English (or Californian English) collectively refers to varieties of American English native to California. A distinctive vowel shift was only first noted by linguists in the 1980s in Southern California and the San Francisco Bay Area of Northern California, helping to define an accent emerging primarily among youthful, white, urban, coastal speakers, first popularly associated with the Valley girl and surfer dude youth subcultures. The possibility that this is, in fact, an age-specific variety of English is one hypothesis; however, certain features of the variety are intensifying and spreading geographically. Other documented California English includes a "country" accent associated with rural and inland white Californians, an older accent once spoken by Irish Americans in San Francisco, and distinctly Californian varieties of Chicano English associated with Mexican Americans. Research has shown that Californians themselves perceive a linguistic boundary between Northern and Southern California.