Hello everybody and welcome to a new video nugget on natural language for communication.

It's a new chapter. We have three video nuggets here. So we're going to talk about communication

phenomena and particular speech acts. We're going to talk about grammars as kind of syntactic

and more specialized counterparts for language models. And then we're going to look at a

couple of more real world problems that appear in communication. That's kind of a teaser

of what could have been done had we more time. Okay. So the first thing I want to talk about

is communication phenomena. And one of the probably most important and influential one

is that the classical view that language consists of sentences that are true or false doesn't

cover everything we need in communication. So 1953 basically introduced a modern view

of language, namely that language is a form of action. And thinkers in this direction

were the philosopher Wittgenstein, Austin and Searle. And the idea is that we use language

as an action to change the actions of other agents to influence them. So we should probably

just remember that we're in a situation where we have a speaker who produces an utterance,

a natural language fragment, which the hearer hears and then processes. And the idea is

that if we view this as an action, then a speech act, this utterance really becomes

a speech act. It not only presents information that it still does, but also performs an action.

Think of this, I think this will become much more clear if we just look at a couple of

examples. So the speech acts are actually things that help the speaker achieve its goals.

So my goal as a speaker might be to inform somebody else. We might want to inform the

agent in the Wampus game of there's a pit in front of you. Then not only do I utter

a sentence that's true or false, but also I want to inform the hearer, the agent in

this case, that they might want to change their behavior. Instead of going forward into

the pit, it might want to go right or left. Another speech act is a querying act. When

I ask a question, can you see the gold? I can issue a command as a speech act. Pick

it up. That doesn't even have a truth value. It's not true or false. Even a question isn't

true or false. You can have the speech act of a promise. I'll share the gold with you.

Or just an acknowledgement, which is also a speech act that tells the hearer that I

understood, I got the message. I might just be able to say something like, okay. Now,

this is totally different from just being true or false. It's an action. Just like actions

we looked at, this issuing speech acts requires planning. Of course, speech act planning is

special. Not only does it depend on the situation, it also depends, of course, on language particulars

like the semantic and syntactic conventions, the protocols of communication that we have.

If you think about military radio protocol, you basically have to terminate every sentence

by over and prefix it by eagle one to eagle two or something like this and terminate the

whole conversation with over and out. Those kind of things all go into the speech act

planning and realization. And of course, you have to take into account the hearer's goal,

what the knowledge base of the hearer is, what you as a speaker anticipate the hearer

already knows, and of course, rationality. Rationality, my own rationality as a speaker

and the rationality of the hearer. It's a complex thing. I'm not going to tell you how

it works. But I just wanted to alert you to the problem of speech acts when we use language

as action. So if we think about what the planning process might be like, even for a very simple

speech act like informing the hearer. So the first thing you have is kind of the agent

has is an intention that wants to inform the hearer that P holds. Then you generate language

and the speaker selects the words in a context C that express P. And then you synthesize

the words. A human would just speak them after selecting. On the hearer's side, this is also

a complex thing. It perceives an utterance, a string of words, but of course, the words

might actually have been changed in the transmission. Say there's a loud noise and you only understand

half of what the words W, the speaker, actually said. And of course, the hearer's context

is slightly different from the speaker's context. The speaker knows different things and perceives

different things. So we have the first problem is that sometimes there is a mismatch between