There was recently a bit of discussion at Language Log over the new term "blawg," meaning a law blog. Mark Liberman remarked that "blawg" and "blog" are pronouced the same, but Benjamin Zimmer responded that they only sound the same if you have the "cot/caught" merger, in which there is no distinction in pronunciation between these two vowels, and hance between the two words. Generally, this merger has occurred in the "midlands," that is, in stripe from the mid-Atlantic states westward. The merger tends to be more common the farther west you are. Wikipedia has the following map, which is pretty nice:
In this map the blue lines enclose the areas where the vowels are fully distinct, and the green lines enclose the areas where they are completely merged. The rest is either transitional or there is insufficient data.
Me, I'm from solidly blue turf. So I thought about it a while, and realized that I use the same vowel for "blog" and "law," namely the vowel from "caught." Thus, I would pronounce "blog" and "blawg" the same, but not "cot" and "caught." Sure enough, John Lawler, who's from the same neck of the woods as me, (I'm from the spinal column of the woods, he's from the esophagus) wrote in to the same effect.
So I got to thinking about all the trouble this merger gets us Chicagoans into. Not like the trouble a different vowel merger causes for a Philadelphian friend of mine, who insists on having her name pronounced "Carrie" with a lax /a/, not "Care-y" with tense /a/, even though I can barely produce this sound. No, the trouble stems from how our dialect is stereotyped. Cast your memory back, if you will, to the SNL skit "The Superfans" - you know, the one with the Chicagoans who discuss the Bears and Bulls in an exaggerated dialect while feasting on something they call "Polish sassage." This always rang a false note with me, and now I know why. Sure, Chicagoans ואני בתוכם front the /ah/ vowel to the point that "hot" could be mistaken by an outsider for "hat," but "sausage" has a different vowel, which doesn't get fronted. But to all those folks from within the green lines on the map above (lines which strike me, I must say, as conservative), "sausage" and "hot" have the same vowel, so if Chicagoans say "hat" for "hot," shouldn't we say "sassage?" But we don't. We may say "cat" for "cot," but not for "caught."
A good number of the actors who played the Superfans were Chicagoans or from the Chicago area - George Wendt, Joe Mantegna, Chris Farley. On the other hand, Farley grew up in Southern California, and Mike Myers, who it must be said has a decent ear for dialects, nevertheless hails from solidly cot/caught merging Canada. My suspicion is that the latter two actors suggested "sassage," and the Chicagoans didn't pick up on the wrongness of it, trusting Farley's Chicago roots and Myers's facility with accents. But the bottom line is that, as any good student of language knows, intuition is no substitute for data; language is so complex that as speakers we are unaware of how we speak. Just because we Chicagoans don't say "sassage" doesn't mean we know we don't. Case in point? Ask just about any Chicagoan what the locals call the city, and they will immediately reply "Chicaahgo." But that just ain't true. Listen to this sample from York University. Wait until the end. Hear that? That's how we say it. Don't let anybody tell you otherwise.