Steve: This is amazing. Well done. But how can you possibly know the degree of mutual intelligibility between two languages you don’t speak or know if something is a language or dialect when you don’t speak it? That seems strange. How is it worked out?
Linguists don’t speak all these languages we study. We just study languages, we don’t necessarily speak them. This is confused with the archaic use of the word linguist to mean polyglot. Honestly, many linguists do in fact speak more than one language, and quite a few of them have a pretty good knowledge of at least some of the languages that they study. But my mentor speaks only Turkish and English though he studies all Turkic languages. I don’t believe he has ever learned to speak any Turkic lect other than Turkish.
In reference to my paper here.
We are not looking for raw numbers. We just want to know if they can understand each other or not.
A lot of it is from talking to native speakers and also there was a lot of reading papers by other linguists. I also talked to other linguists a lot. Linguists typically simply state if two lects are intelligible or not. Also there is a basic idea among linguists of what the boundary is between a language and a dialect, and I used this knowledge a lot.
Can they understand each other? Yes or no. That’s pretty much about it. Also at some degree of structural difference, we can see the difference between a language and a dialect. It’s a judgement call, but linguists are pretty good at this.
There is a subsection of very loud linguists, mostly on the Internet, who like to screech a lot about this question cannot be answered by answered because of this or that red herring or some odd conundrums that work their way in. The thing is if you ask around enough, you will be able to get around all of the conundrums and you should be able to eventually reconcile all of the divergent responses to get some sort of a holistic or “big picture.” You finally “figure it out.” The answer to the question comes to you in a sort of a “seeing the answer as part of a larger picture” sort of thing.
The worst red herring is this notion that speakers from Group A will lie and say they do not understand speakers of Group B simply because they hate them so much. If this was such a concern, you would have think I would have run into it at some point. A much worse problem were ethnic nationalists who lie and say that they can understand neighboring tongues when they can’t.
The toxin called Pan-Turkism or Turkish ultranationalism comes into play here. It is almost normal for Turks to believe that there is only one Turkic languages, and it is called Turkish. All of the rest of the languages simply do not exist and are dialects of Turkish. I had to deal with regular attacks by extremely aggressive Ataturkists who insisted that any Turk could easily understand any other Turkic language. Actually my adviser told me that my piece would not be popular with the Pan-Turkics at all. I don’t really care as I consider them to be pond scum.
Granted, some of it was quite controversial and I got variable reports on intelligibility for some lects like Siberian Tatar vs. Tatar, the Altai languages, Kazakh vs. Kirghiz, Crimean Tatar vs. Turkish.
Where native speakers differ on such questions, often vociferously, you simply ask enough of them, talk to some experts and try to get a feel for that what best answer to the question is.
Some cases like Gagauz vs. Turkish probably need raw intelligibility testing. That’s the only one that is up in the air right now, but it is up in the air because the lects are so close. Intelligibility between Gagauz and Turkish is somewhere between  70-100%. In other words, they have marginal intelligibility at worst. My Gagauz expert who knows this language better than anyone though feels that Turkish intelligibility of Gagauz is less than 90%, which is where I drew the line at language and dialect.
It is also starting to look like Nogay is a simply a dialect of Kazakh instead of a separate language, but that might be a hard sell.
Some of these are seen as separate languages simply because they are spoken by different ethnies who do not want to be seen as part of the same group. Also they have different literary norms. Karapalkak is just a Kazakh dialect, but the speakers want to say they speak a separate language. Same with Bashkir, which is simply a dialect of Tatar. The case of Kazakh and Kirghiz is more controversial, but even here, we seem to be dealing with one language, yet the two dialects are spoken by different ethnies that have actually differentiated into two separate states, each with their own literary norm. Kazakhs wish to say they speak a language c called Kazakh and Kirghiz wish to say they speak a language called Kirghiz although they are probably really just one language.
We see a similar thing with Czech and Slovak. My recent research has proven that Czech and Slovak are actually a single language. But the dialects are spoken by different ethnic groups who claim different cultures and histories and they have actually divided into two different states, and each has its own literary norm.
It is here, where dialects become languages not via science by via politics, culture, history and sociology, that Weinrich’s famous dictum that “a language is a dialect with an army and a navy” comes into play.
Scientifically, these are all simply dialects of a single tongue but we call them languages for sociological, cultural and political reasons.
Alpha Unit
Robert A. Lindsay