Sarcasm is proverbially said to be the lowest form of wit. It is often associated with the use of irony. Hostile, critical comments may be expressed in an ironic way such as saying "don't work too hard" to a lazy worker. The use of irony introduces an element of humour which may make the criticism seem more polite and less aggressive but understanding the subtlety of this usage requires second-order interpretation of the speaker's intentions. This sophisticated understanding is lacking in people with brain damage, dementia, autism and this perception has been located by MRI in the right parahippocampal gyrus.  Chandler Bing is undoubtably one of the most famous examples. He frequently responds to friends in these ways most of the time.
Tom piper) An Ironicall [Sarcasmus], spoken in derision of these rude wits, whych make more account of a ryming rybaud, then of skill grounded vpon learning and iudgment.
In certain Ethiopic languages, sarcasm is indicated with a sarcasm mark, a character that looks like a backwards question mark at the end of a sentence, similar to Alcanter de Brahm's proposed irony mark (؟).