When we talk to each other, we interact in ways that go beyond telling each other about ourselves and the world around us. We let our interlocutors know we think and feel; we can share our attitudes towards each other and the things we talk about. We do this by using language dedicated to interaction and which does not contribute to the content of what we say. The mood of a conversation changes dramatically when the language of content (you made it) is enriched with interactional language (oh wow), bold-face in (1-2).
(1) Ann: Oh wow, you made it, eh?
Beth: I know, right?
(2) Charlie: Damn. I’m sick.
Dorian: Oh no! Get better, okay?
Without interactional language the conversation sounds almost curt or even rude. It’s like you don’t really care. In spoken language, this may be alleviated by other means such as intonation, gestures, and facial expressions and in texting via emojis. But in the absence of such clues, when Beth responds to Ann’s observation that she made it with a simple I know it takes away the congratulatory attitude of the preceding utterance. Beth may almost come across as complaining that Ann said something she already knows, so why bother? And there is no indication as to whether Beth is in fact excited about the fact that she made it. Similarly, in the second example, if Dorian responds with a simple get better, there is a sense in which he might as well say: So what? All you have to do is get better. No empathy. No connection.
By adding interactional language, the interlocutors learn something about how the other feels: oh wow conveys Ann’s surprise and excitement, oh no conveys Dorian’s concern for Charlie. By adding the sentence-final particles eh, right, and okay, the interlocutors build a connection: they indicate that they care what the other thinks and feels rather than simply telling them what to think and do or how to feel. They indicate that the speaker wants a response. Thus, interactional language has two interrelated function: it helps us to synchronize our minds in that it allows interlocutors to get a glimpse of what is going on in their interlocutor’s mind. And it helps us to facilitate the flow of the interaction. Being encouraged to respond makes it easier to keep the conversation going and thus to further connect with the interlocutor. The connection we are able to establish via interactional language may even be an emotional substitute for a physical hug. (In the situations in (1-2), hugs would be appropriate.) Especially when physical hugging is not a possibility.
Some self-help websites have lately advocated for giving “verbal hugs”. You find statements like “a verbal hug is a sincere acknowledgment, said to make the person feel warm, loved, and honored. For example, instead of greeting someone with the trite “How are you?” try “It’s so good to see you,” or, if it’s true, “You’re looking great.” (https://growyourkeytalent.com/2019/02/giving-verbal-hugs/)
Now the thing about the language of content is that they it can be used to lie (hence the above cited post emphasizes to say it only if it is true). But interactional language is not about truth or falsehood: one cannot lie by saying oh wow. One could, of course fake it, but that would be like faking a smile or… a hug. While humans do not seem to be inherently equipped with lie-detection abilities, they are very good at detecting fake smiles and fake hugs. And, I would add, that we are also good at detecting fake verbal hugs that are delivered via interactional language. It’s much harder to fake interactional language than it is to lie with the language of content because the rules that regulate its use are much more difficult to make conscious. (Just ask someone what “eh?” means). And hence interactional language, arguably, allows for an unobstructed window into your interlocutor’s mind and their emotions.