It's well-known that you should size your input fields to the amount of text you want the user to write. There's an example of that on this very page: even though the "Your answer" field can stretch to fit any size of text, the default size is about a dozen lines, to discourage users from writing one-line answers.
I'd like to know more details on the relationship between input field size and user behaviour, if that relationship is generally known. Put simply, how big should the field be for a given desired input length? Of course, writing more or less text isn't the only possible outcome of putting a larger or smaller field: users might just walk away (thinking the form's not for them). How big a problem is that?
Most importantly, how much does your answer depend on the type of input? Is the relationship the same for feedback forms, posts to fora/communities, comments on other users' content, &c.? I'd assume it depends on language too, but I'm only interested in English.