Sarcasm has a two-faced quality: it's funny and mean.

Some language experts suggest sarcasm is a gentler way to criticize with indirectness. "How do you keep this room so neat?" Other researchers have found the mocking nature of sarcasm as more hurtful than plain-spoken criticism.

Sarcasm can express our expectations as well as our disappointments.

When rain spoils an outdoor picnic, and you say, "We picked a fine day for this," it means you had hoped it would be sunny and you're unhappy about the rain.

Not everyone thinks sarcasm is funny. There is also not just one way to be sarcastic. Sarcasm can be implied with pitch, tone, volume, pauses, duration, and punctuation.

Facial expressions can also indicate sarcasm. Expressions around the mouth, instead of the eyes, were most often cited as a clue to a sarcastic statement.

The inability to understand sarcasm may be a warning sign of brain conditions.

Scientists found that autism, closed head injuries, brain lesions, and schizophrenia can interfere with the ability to understand sarcasm. People with frontotemporal dementia have difficulty detecting sarcasm. The loss of the ability to pick up on sarcasm could be used as an early warning signal to diagnose the disease.