Are the slave and regional dialects in Mark Twain's literature historically accurate?

[astro]

Per this other thread has there ever been a study or investigation as to the accuracy of Mark Twain’s extremely thick slave and regional dialects used in his literature or do we just take it on faith that they are correct?

[sugaree]

I believe that historians actually rely on written dialects, as well as the rare turn-of-the-century recordings of people, to reconstruct ninteenth century accents and pronounciations.

[RealityChuck]

It’s accurate to say they reflect Twain’s perception of the dialects. Hard to tell how accurate his perception was, however.

[Exapno_Mapcase]

Twain himself put an “Explanatory” note at the beginning of the novel:

In this book a number of dialects are used, to wit: the Missouri negro dialect; the extremest form of the backwoods South-Western dialect; the ordinary “Pike-County” dialect; and four modified varieties of this last. The shadings have not been done in a hap-hazard fashion, or by guess-work; but pains-takingly, and with the trustworthy guidance and support of personal familiarity with these several forms of speech.

The critical introduction to this edition, by Henry Nash Smith, says:

His claim to care in the representation of dialects is borne out by a comparison between the manuscript of about two-thirds the novel … and the published text, which reveals thousands of changes in spelling and diction evidently made for the sake of accuracy of transcription. But even if we could prove that the dialects are accurately rendered (which we could do only by a difficult historical inquiry into the language actually spoken along the banks of Mississippi in the 1840’s) we should still have thrown very little light upon the novel as a work of art.

This edition is pretty old (1958) and much research has been done along these lines since, so it’s possible that someone has put in the time to make the comparisons. But my understanding is that it is generally acknowledged that the shadings of dialects was one of the pieces of genius that went into the novel.