Cousin Shane sent me this fun little quizzie [insert classic punchline here]. He took it, his Dad took it, I took it, and Ken took it. We all ended up at 43-44%, just barely into the Yankee range. (The quiz is just about terms and expressions and local usage, if you choose not to take it.)
I found this pretty fascinating (but then I used to read the dictionary when I was a kid and bored--I just love words and their origins), because it appears that northern Indiana is not all that Yankee is their speech. You'd think we'd be a little less southern-fried, but not so. My friend Jim took it, and he was 55% or something like that, into the Dixie side. I chalk it up to my Mom's side of the family, which comes from Kentucky. (I can't explain Jim's aberrant speech patterns. Ha! Love ya, Jimi.) We also have lots of relatives that live in Kentucky, Georgia, and Florida, so we've always picked up a bit on their accent. I still say "y'all."
Indiana itself is very different in accent when it comes to which area you live in. It's a rather long state, and once you get south of Indianapolis, the southern twang is very apparent. In my area, we're a little more "Chicaaaahgo." And don't get me started about the 5 years I spent in Nort' Dakohhhta.