Amy Clark writes beautifully about the power and pitfalls facing writers who try to capture authentic regional accents and cadences. Among her admonitions to writers tempted to take the easy route is this gem:
Finally, vernacular speech should never be used to suggest that one character is less intelligent than another, a myth about dialect and cognition that was debunked by linguists half a century ago and many times since. Nonstandard grammar patterns such as double negatives or the leveling of irregular verbs like blowed for blow tend to be the most stigmatized of dialect patterns, though their origins and usage are historical and cultural.
Good advice not only for writers but for all of us.
Mitch Speers 