The first scientific paper I wrote states, in the second paragraph, that “language depends on two mental capacities with distinct neurocognitive underpinnings”: vocabulary and grammar. To understand cats are mammals, all you need to know are the definitions of CATS, ARE and MAMMALS, plus the grammar involved. This was how I was trained to think about language. I knew that there were probably some other aspects of language (like phonology), but they seemed peripheral.
That worked well enough until I came across sentences like this:
Bill is tall.
There are many people named “Bill,” and tall is relative both to Bill (Bill may be a tall Pygmy) and to the speaker (who may be a Pygmy). Understanding this sentences seems to require more than just dictionary definitions. It gets worse:
Abby: Would you like some coffee?
Betty: Coffee would keep me awake.
Betty is either refusing coffee or accepting coffee, depending on whether she wants to stay awake. She also assumes Abby can figure this out for herself. Now, consider:
Woman: I’m leaving you.
Man: Who is he?
This dialog is easy to understand, but a dictionary and a grammar book would get you absolutely nowhere. This is not a minor, peripheral problem either. In case you think I’m cherry-picking examples, here are the first two sentences from today’s review of Rebuilt:
A popular question when trying to start a pseudo-intellectual conversation is whether you would rather lose your sense of hearing or sense of sight. Almost invariably, the answer would be to retain one’s sight; it seems people are more worried about being able to drive alone than hearing a fire alarm.
Notice that the author assumes we know that “the answer” referred to in the second sentences is the answer to the question in the first sentence. Also, what does retaining sight have to do with being afraid of driving alone vs. hearing a fire alarm? We have no difficulty making these connections, but it didn’t have to be that way. Try reading these two sentences (or anything else) as if you were a robot, and you will find many more non sequiturs. Even careful, patient writers leave much unsaid, yet we usually read between the lines without ease, not even noticing.
I wish this post was going to be an explanation of how we accomplish this task. I have no idea. There is some decent theoretical work on this subject, but relatively little empirical work. I have a couple studies running now, including this 5-minute experiment you can do online (shameless self-promotion, I know).
Interestingly, Steven Pinker, whose work inspired that first study of mine (read about it here) has also begun working on the inferences that underlie language, and we are currently discussing a collaboration.
If you want to stay informed and even join in the conversation as I try to piece together this puzzle, you can read more about inference and language my Cognition and Language blog at my laboratory website.