Intrigued by the concept of phatic expressions: messages whose only purpose is to confirm the channel is working. The canonical example is when we walk by someone and say "what's up?" No information beyond mutual acknowledgement is communicated. There is a related, nuanced concept called backchannel that represents speaker/listener confirmation. When one person is monologuing, the listener is seldom completely silent. To confirm that the messages are being received (and understood), the listener will nod or punctuate with "yes" or "go on". It's almost impolite not to make such statements, and this ties back into the idea of the phatic as "social grooming".
Moving one level up from phatic, we can see how such statements fit in communication as a whole via Jakobson's functions of language. The framework for these functions are the elements of communication:
By Artist2426 - Own work, Public Domain, Link
Different functions of language will emphasize the different elements in the diagram above. Phatic emphasizes the channel. Here's the diagram amended with Jakobson's functions:
Daniel Chandler's Semiotics for Beginners has a good table mapping the element, function, and an example for each. Modified here:
Element | Function | Use | Example |
context | referential | imparting information | It's raining. |
sender | expressive | expressing feelings or attitudes | It's bloody pissing down again! |
receiver | conative | influencing behaviour | Wait here till it stops raining! |
channel | phatic | establishing or maintaining social relationships | Nasty weather again, isn't it? |
code | metalingual | referring to the nature of the interaction (e.g. genre) | This is the weather forecast. |
message | poetic | foregrounding textual features | It droppeth as the gentle rain from heaven. |