Today’s Great Idea in Linguistics comes to use from syntax. One interesting difference between syntax and other fields of linguistics is what is considered compelling evidence for a theory in syntax. The aim of transformational syntax is to produce a set of rules (originally phrase structure rules) that will let you produce all the grammatical sentences in a language and none of the ungrammatical ones. So, if you’re proposing a new rule you need to show that the sentences it outputs are grammatical… but how do you do that?
One way to test whether something is grammatical is to see whether someone’s said it before. Back in the day, before you had things like large searchable corpora–or, heck even the internet–this was difficult, so say the least. Especially since the really interesting syntactic phenomena tend to be pretty rare. Lots of sentences have a subject and an object, but a lot fewer have things like wh-islands.
Another way is to see if someone will say it. This is a methodology that is often used in sociolinguistics research. The linguist interviews someone using questions that are specifically designed to elicit certain linguistic forms, like certain words or sounds. However, this methodology is chancy at best. Often times the person won’t produce whatever it is you’re looking for. Also it can be very hard to make questions or prompts to access very rare forms.
Another way to see whether something is grammatical is to see whether someone would say it. This is the type of evidence that has, historically, been used most often in syntax research. The concept is straightforward. You present a speaker of a language with a possible sentence and they use thier intuition as a native speaker to determine whether it’s good (“grammatical”) or not (“ungrammatical”). These sentences are often outputs of a proposed structure and used to argue either for or against it.
However, in practice grammaticality judgements can occasionally be a bit more difficult. Think about the following sentences:
- I ate the carrot yesterday.
- This sounds pretty good to me. I’d say it’s “grammatical”.
- *I did ate the carrot yesterday.
- I put a star (*) in front of this sentence because it sounds bad to me, and I don’t think anyone would say it. I’d say it’s “ungrammatical”.
- ? I done ate the carrot yesterday.
- This one is a little more borderline. It’s actually something I might say, but only in a very informal context and I realize that not everyone would say it.
So if you were a syntactician working on these sentences, you’d have to decide whether your model should account for the last sentence or not. One way to get around this is by building probability into the syntactic structure. So I’m more likely to use a structure that produces the first example but there’s a small probability I might use the structure in the third example. To know what those probabilities are, however, you need to figure out how likely people are to use each of the competing structures (and whether there are other factors at play, like dialect) and for that you need either lots and lots of grammaticality judgements. It’s a new use of a traditional tool that’s helping to expand our understanding of language.