How different were high medieval Latin dialects from different parts of Europe?

Question

There are some regional differences in contemporary Ecclesiastical Latin, mostly in pronunciation (for example, "c" before e/i can be pronounced as [ʧ] or [ts]). Also, I know that as non-natives, medieval Latin speakers sometimes introduced words from their native languages. On the other hand, various dialects were at least somewhat mutually understandable. My layman guess is that they differed about as much as various dialects of contemporary English, or little more.

For example, let's pick 13th century and Latin dialects spoken in Italy, British Isles, Sweden and Bohemia - if people from these regions met, how difficult would it be for them to understand each other, and what would be the main differences?

No need to describe these particular dialects in detail though, it's just an example.

EDIT: Let's take modern ecclesiastical Latin as a reference. Speakers of some of the different dialects may need some time to accommodate to even understand each other, and the differences may be funny. Do we have any evidence that high medieval Latin dialects were more, less or about as different as those in ecclesiastical Latin today?

An example of various dialects together is here (mostly in ecclesiastical Latin, with French introduction). The differences are probably slightly exaggerated to enhance the fun effect, but only dialects of Western Europe and America are included, other dialects like Polish one have other peculiarities.

Answer 1

I can't speak to the particulars of any of those dialects, but it seems that historical evidence would indicate that in your hypothetical meeting, everyone would understand each other quite well:

1. It was common for teachers in medieval universities to move around. Famously, around the time period you ask, Aquinas taught in Paris even though he was from Italy.

2. You can look at collections of letters from the Medieval age, to get a sense of how people communicated: communication from England to Germany, communication between the pope and the queen of France, and so on.

3. We have examples of a number of large gatherings around this time period: the Medieval councils of the Catholic Church. The participants were from across Western Europe (the Latin-speaking world), and I'm not aware of any reference that language was an issue.

Answer 2

Q" "For example, let's pick 13th century and Latin dialects spoken in Italy, British Isles, Sweden and Bohemia - if people from these regions met, how difficult would it be for them to understand each other?"

A: If we are talking about oral communication in Latin, then the answer is that most likely they did not understand each other very well.

cf. Rigg 1996/1999 (p. 80):

Obviously, these differences didn't happen overnight.

For instance, Allen (Allen 1978) writes that

"Latin in France had been pronounced along national lines from earliest times, with a particular disregard for vowel-length and accentuation" (p. 106) or

Waquet 1998 (English translation by John Howe, 2001): "In France, where from the thirteenth century onward Latin had degenerated in both vocabulary and syntax, Latin was pronounced like French" (p. 164).

It led to confusion and incomprehension in the 16-19 centuries. In extreme cases, Waquet writes, "speakers could be totally unaware that they were speaking the same language, but more usually communication would be garbled by different pronunciations of the same letter" (p. 163). She mentions very interesting examples in Chapter 6, Oral Latin.