To me, the point of these pseudonumeric words is that they are approximate.
If I *knew* there are exactly two things, I could say "two". Whereas, a "couple of things" means a "fuzzy" two. It might be two, it might be three, and the distinction's not important enough for me to force an exact count --- and I don't want to pretend more accuracy than I have.
I think of "a couple" as a distribution curve centered on 2. It's not a normal distribution; 3 is much more likely than 1. In rare cases, "a couple" might be able to cover as many as 4 items... because it's a distribution. But if the "couple" is getting that off-center, I should probably up my estimate to the next pseudonumber: a few.
It's all about the PRECISION, baby
If I *knew* there are exactly two things, I could say "two". Whereas, a "couple of things" means a "fuzzy" two. It might be two, it might be three, and the distinction's not important enough for me to force an exact count --- and I don't want to pretend more accuracy than I have.
I think of "a couple" as a distribution curve centered on 2. It's not a normal distribution; 3 is much more likely than 1. In rare cases, "a couple" might be able to cover as many as 4 items... because it's a distribution. But if the "couple" is getting that off-center, I should probably up my estimate to the next pseudonumber: a few.