sarcasm is used a lot here in NZ, along with irony. apparently it makes you cool, or clever, or smart, or something.
its incredibly damaging.
sarcasm is not a natural, first order, linguistic construction. its pretty sophisticated. it requires the listener to a) detect that the sarcasm is not true b) understand that the opposite is meant c) not take it personally.
in our heads is a brain. it learns language quickly. the learning of language requires repetition, accuracy, feedback and truth from other people. If you feed a neural network nonsense and lies, it becomes a crap neural network.
fortunately, we get most of that when we grow up. There is a small disjoint in the learning of emotional language (parents often lie about emotional issues to 'protect' their children. unfortunately that means they teach their children to not listen to the truth of their incredibly perceptive emotional systems), and a small disjoint around fairy tales (god as an old man in heaven, father christmas, the easter bunny, tooth faires and other such things). still, our brains are resilient and cope. maybe a little untruth is useful at times, as it teaches us to learn to spot it?
at any rate, underlying our language skills is this truth based network. we learn to take things at face value. we later learn to not trust - to spot if someone is lying. we develop (ego based) mechanisms to protect ourselves form untrustworthy individuals, and filter everything they say.
and then comes sarcasm. its fine if used by an untrusted stranger. it is deftly caught by the ego defense system and filtered before it causes upset. it cannot touch us, unless its use shatters a desired projection of behaviour or situation. but. since people think it is clever, and witty, they use it on friends, and lovers, and children. this is appalling. the point of friendship is that you can DROP your ego defense system. you can be yourself and easy without armour. so those comments slip straight past, perhaps triggering a reflexive defense in passing. and they hit the linguistic system unchanged. suddenly the sarcastic "you're so fat" loses its sophisticated meaning and says exactly what is written. the sophistication level is bypassed (along with the caught out ego). a source of trusted information/feedback supplies incorrect information and one's model of reality becomes skewed. was that the intention of the sarcastic individual? i doubt it. i bet they thought it was clever.
worse is its use with a child. they do not have the ego defense systems properly active yet. that 'oh so witty' sarcastic adult remark is going to be resonating around their systems for years before it can be rebuffed, if at all.
that said. there IS a way to use sarcasm and irony. consciously. with positive results. this is the truly sophisticated use. next time someone fails to perform well, or is a total arsehole, and is in a reflective assessment mode. (ie, they are thinking about their behaviour), try being sarcastic. "that was really well done". or "wow, you never cease to amaze me", or "i think you are incredible for doing that".
the ego defense system will pick it up and glean the true meaning (alowing higher order adult integration of the message), and the raw words themselves will breeze through and implant themselves in the underlying systems. positive messages for future improvement of (low level, non-ego) self image.
you can use it on yourself, too. always good to test these things on a willing subject first.