In linguistics, a phatic expression is one whose only function is to perform a social task, as opposed to conveying information. Small talk and polite exchanges concern the channel of communication, but the words do not carry literal meaning.
Speaker one: “What’s up?”
Speaker two: “Hey, man, how’s it going?”
Neither expects an answer to his/her question. Much like a shared nod, it’s an indication that each has recognized the other’s presence and has therefore performed sufficiently that particular social duty. (via Wikipedia)
Is there an equivalent in interaction design? Is it merely filler or are is there a functional role, intentional or otherwise?