Blurb:

Language is not always specific. In normal language use the speaker (or writer or signer) and the addressee are expected to be cooperative. The speaker is expected to be able to estimate what the addressee knows and does not know. If the speaker gives too little information, the addressee will not be able to interpret what was said. If the speaker gives redundant information, the addressee might be confused or insulted. There is an old joke that circulates among children, ‘Why do firemen wear red braces?’ The answer is, ‘To keep their trousers up.’ Here the person who poses the question is being uncooperative by including the adjective ‘red’ and then giving an answer in which colour is irrelevant. Teasing jokes like these are common in books of jokes for children.