...but what I'm wondering is, does inventing a word for a concept actually create that concept? Or is it more a reflection of an experience that previously existed, but just didn't have a label until that point? My guess is that it's some combination of both, but I'm not sure how much each (creating reality verses reflecting reality) plays into it.
I have no clear take on this either, but I do have some preliminary thoughts. Cognition is a single process. Focussing on something is a sort of repition of attention, and that's what gives rise of concepts. So when we "see" something, when we become concsious of something as a unified whole, we're already creating a meaningful unit. Words are objects, in that sense, too. Here we are, with our inscrutible cognition soup, linking memory, thought and words. That sounds awefully complicated, but the key here is that both words and the things that we use words to refer to are objects that present themselves to us.
Now, a concept is a bundle of cognition. There are words whose meanings we don't know. There are concepts we can't quite pin down with words. It's not a one-to-one relation, because we only have one mind in which all of this is mixed up. Take abstract words, such as "love" or "soul" or "justice". You're very likely to have heard those words before you've ever developed that level of abstraction, so you start speaking with the assumption that these things exist. They're probably word-first concepts: you figure out what people mean when they talk about this, and this is a social process. Other words clearly describe things that you've encountered before: words for your favourite food, for example, make it easier to express what it is that you want, but the desire is pretty familiar, and so is the object of desire. So, for example, you can crave a cookie without knowing how to ask for one, and finally being able to ask for one is a boon. These I call thing-first concepts.
I find the distinction is especially interesting when it comes to writing fiction. You create words for things that don't exist, which is especially important for SF & F, but it's also sort of relevant for figurative language. There's no thing-correlate for a pun, for example, but it can still have real effects by forging cognitive connections. It's a mess, really.
But basically, I think it helps to remember that words themselves are both concepts and things, too. So when other people name a concept, and the concept isn't that important to you but the person is, then you mix that in with concepts that are personally meaningful to you. This can lead to intricate conflicts of interest: for example, the availability of some words may block the wide-spread acceptance of others, but the word that wins out may be almost, but not quite there.
For example, I'm an "atheist", but that term doesn't actually describe what I am - it describes what I am not. However, when I use the word "atheist" to describe what I am not, I use the syntax I would use to describe what I am. This leads to a lot of problems regarding "atheism is just another believe", and I can fall into that trap myself. A similar problem occurs with the distinction between "atheism" and "agnosticism". The assumption that words have objective meanings can cause problems, here, by making it hard to articulate difference, when the language systematically favours one point of view over others.
I don't think there's such a thing as an innate language faculty, and I think that all meaning is inherently subjective. But I think that subjectivity in itself has traits that you can look at; that is my subjectivity is an object when looked at, and so is yours, and so is everyone else's, and that's why we can communicate in the first place.
I said I have no clear take on this issue, but the direction I'm thinking in is language as a social arena to negotiate meaning. A thing we share, so we can talk about things we have in common and things we don't. My hunch is that language does shape the way you think, but not in a way that's unique to language. I think it's just a sub-type of "living with others". Shaking hands, crossing streets, buying dinner, talking, going to bed. But I'm not confident about that at all, and I haven't really worked it out to my satisfaction. It's just the direction I'm thinking in.
(I love this thread, so thanks for making it.)