Linguistics
Conversation runs on a hidden contract: assume everyone's trying to be useful
Philosopher H.P. Grice argued conversation only works because speakers and listeners silently agree to be truthful, relevant, clear, and no more informative than necessary. Break one of these 'maxims' - say something oddly vague or beside the point - and listeners don't conclude you've malfunctioned, they infer a hidden meaning instead. That silent inference is how sarcasm, hints, and tactful evasions get decoded without ever being spelled out.