Sometimes people say something that you understand perfectly well, but if you stop and think about it, it doesn't make literal sense. I know, right?
There are those who argue that "I know, right?" is stupid and meaningless, and that we should stop using it. After all, when you say it you're not really asking whether or not you know.
But "I know, right?" is a great example of how language actually works. Language is not just a means of passing literal information. Welcome to the world of pragmatics: the study of speech as behavior intended to produce effects on an audience.
Language carries a lot of extra implications, just like physical gestures. For instance, if you point to something, how you point to it shows your attitude toward it — and toward the person you're showing it to. The same goes for what you say and how you say it: "The washroom? Yes, it's over there." "That way." "You just walk over there and you will see it." "It's in that direction, sir."
Sometimes, physical gestures don't literally look like what they really are for. When you shrug, you don't literally have something you're trying to get off your back or protect your head from. When you wink, you're not doing it because there's something in your eye. When you bow… do you even have an idea of what that would accomplish? The same can be true with words. If you start a sentence with "Well," what are you saying is well? If you say "There is something here," is the something there or here? Why do we say "by the way" when we don't even know which way we're talking about? Are you shrugging right now?
It's always about the effect we're trying to have on the other person, and what we want to imply about the relationship between us and them and our attitude toward the situation and topic. Conversation is a dance, and you have to know the steps and work with your partner.
All this brings us back to "I know, right?" Consider what we're actually doing when we say each of its two parts.
If you say "I know," what you mean by it depends on how you say it. If your spouse says, "My mother is coming to visit," and you say, "I know," does that mean "You've told me this already and I don't feel like talking now," "I've already made a grocery list for her," "I'm aware and not looking forward to it," "I'm aware that you're looking forward to it and I'm happy for you," "I'm aware that you're not looking forward to it and I'm commiserating with you," or what? It depends on the intonation. When you hear it in "I know, right?" the emphatic intonation shows that this is a fact that you are very aware of and find quite striking.
If you say "Right?" it can mean "Is that correct?" but it can also mean "Do you agree with me?" It reaches out to the other person — it requires a response, but it gives the other person the upper hand. Of course, when the person has just told you the thing you're saying "Right?" to, you're obviously not literally asking if what the person told you is correct. The "Right?" gesture is referring to the "I know!" gesture: you're asking the person to confirm the reaction you have to it. You're trying to build a shared experience, a social bond. The fact of asking for confirmation also implies that the topic may be subject to question or in some way not obvious — that other people are surprised by it, or perhaps that you were.
So "I know, right?" communicates first that the fact is striking and impinges significantly on your personal experience, second that you are seeking confirmation of its strikingness, third that you are presenting it as something that is not universally obvious and agreed upon even though it should be, and fourth that you are seeking to create a bond of shared perspective and emotion between you and the person you're talking to.
"I know, right?" has been popular for awhile now. It was used in the movie Mean Girls in 2004, and many people trace its popularity to that. But it already had an Urban Dictionary entry by then. Jimmy Fallon used it on Weekend Update on Saturday Night Live in November 2000. Since Tina Fey was head writer at SNL then, and since she wrote Mean Girls, she's probably a prime vector for it.
Couldn't we instead say, "I find that striking, and I hope you agree"? Not really — it doesn't sound at all the same, does it? The attitude expressed is very different. It's less fun and less fashionable too. It's even at least a bit different from what, as linguist Mark Liberman has pointed out, people might have said a century ago: "Yes, isn't it?"
Does that mean that a lot of people are feeling the "I know, right?" way now when they didn't before? It really just means it's a popular performance of an attitude for effect. People like to pick up fun things other people are doing and use them too. If they didn't, we wouldn't have language. And fun things go through fashions in everything: clothing, dance moves, language…
