Scientists have discovered comedy central in the brain — specific tissue regulating the ability to understand sarcasm.

People with damage to the right frontal lobe, right behind the eyes, are unable to appreciate this kind of humor.

In sarcasm, "the literal meaning is different from the true meaning, and some people just don't understand that difference," said Simone Shamay-Tsoory, a psychologist at the Rambam Medical Center and the University of Haifa in Israel. Her study is in the May issue of the journal Neuropsychology.

For instance: Joe fell asleep at work. His boss walks by. "Don't work too hard, Joe," he says. Normal volunteers and people with damage to the back of the brain understood that the boss was being sarcastic. But Shamay-Tsoory said that people with damage to the right frontal lobe didn't get the irony of the comment and failed to understand that the boss was not happy with his lethargic employee.

Shamay-Tsoory says that apart from brain injury, perhaps even subtle differences in the "wiring" of this region can leave people unable to empathize, and it is this lack of ascertaining another's emotional state that may be responsible for the inability to understand sarcasm.

Sarcasm is used in social situations as an indirect way of expressing criticism, she said. The network that regulates one's ability to appreciate sarcasm begins with an understanding of the meaning of the sentence, which is carried out by the left frontal lobe. Then the right frontal lobe helps put it into a social context. Finally, the right frontal lobe must be able to differentiate between the literal meaning and what is really meant.

Dr. Antonio Damasio, head of the neurology department at the University of Iowa College of Medicine, said this finding made perfect sense. "People with damage on the right side of their brain … have major problems with social cognition, or thinking," he said.