The short answer is: a lot. To a language connoisseur¹ like moi, an accent is both something to emulate (as when learning a new language) and something which provides an immense amount of data about a person.
When I open my mouth and speak in English, it’s clearly with an American accent, but it’s not the accent of the people I grew up around. My BFF has a strong Midwestern way-a-talkin’, but I never picked it up. Additionally, people trained in elocution have a hard time pinning down where I’m from.
This is just one of the things I think about a lot, but then the Times went and ran a story about the completion of the Regional Dictionary this past week. As it’s about two of my favorite things, reference books and the ways people speak, I had to check it out. It was totally fascinating, but also bewildering. It turns out that I use the North Midland dialect which partly fits, as I grew up in the region, but I do fall into the cot-caught merger (pronounce both words the same) which most of my peers did not.
In the end, all of this works out in my favor. I can name most American accents with a pretty high degree of accuracy, but not many people can tell mine.
In Spanish, I have a way of speaking that the Iberians sometimes identify as “de fuera” [from outside, i.e. not local] but they’ll guess that I’m from another region or maybe Italy. Conversely, I can tell which part of the Spanish-speaking world someone is from as well as point out a Catalan, a Madrileño or a Galician.
In France, I haven’t gotten anywhere as good yet, though in groups of three or more, I can tell who isn’t local. My own accent is apparently even harder to trace than in Spain, which makes me feel like I’m somehow pulling a fast one on everyone. People here seem a little more aware of the outside world so when they look at me, they have one idea about my nationality, but when I speak and say things like, “yeah” which they hear as ja (German), they get really confused which is all part of my master plan.
¹In English, we say connoisseur, since the word has been in use since the French first came into contact with the Anglo-Saxons. In modern France, they say connaisseur, since the verb root (connaître, to know) is now conjugated –ais instead of –ois.