Studies have shown that sarcasm enhances problem solving. An inability to understand it can be an early warning sign of brain disease:
Sarcasm so saturates 21st-century America that according to one study of a database of telephone conversations, 23 percent of the time that the phrase “yeah, right” was used, it was uttered sarcastically. Entire phrases have almost lost their literal meanings because they are so frequently said with a sneer. “Big deal,” for example. When’s the last time someone said that to you and meant it sincerely? “My heart bleeds for you” almost always equals “Tell it to someone who cares,” and “Aren’t you special” means you aren’t.
“It’s practically the primary language” in modern society, says John Haiman, a linguist at Macalester College…
The Dish 