New research suggests that the highest functions of our brains handle the lowest form of wit.
The research has found that the ability to understand sarcasm depends on a carefully orchestrated sequence of complex cognitive skills in specific parts of the brain.
Dr Shamay-Tsoory, a psychologist at the Rambam Medical Centre in Haifa and the University of Haifa, says that sarcasm is related to our ability to understand other people's mental state and is not just a linguistic form, it is related to social cognition.
The research revealed that areas of the brain that decipher sarcasm and irony also process language, recognise emotions and help us understand social cues.
Simone Shamay-Tsoory and colleagues say that understanding other people's state of mind and emotions is related to our ability to understand sarcasm.
The team recruited 41 people who had suffered mild brain damage following accidents or illness together with 17 healthy volunteers, and the scientists looked at how they understood neutral and sarcastic statements read by actors.
One sarcastic example was, "Joe came to work and instead of beginning to work he sat down to rest. His boss noticed his behaviour and said 'Joe don't work too hard'."
In the neutral version, Joe begins to work as soon as he arrives and his boss's reaction is the same.
The study showed that people with damage in the prefrontal lobe struggled to pick out sarcasm. The others, including people with similar damage to other parts of the brain, were able to correctly place the sharp-tongued words into context.
The prefrontal lobe is known to be involved in pragmatic language processes and complex social cognition. The ventromedial section is linked to personality and social behaviour.
Dr Shamay-Tsoory said the loss of the volunteers' ability to understand irony was a subtle consequence of their brain damage, which produced behaviour similar to that seen in people with autism.
She says they are still able to hold and understand a conversation, but problems arise when people talk in indirect speech and use irony, idioms and metaphors because they take each sentence literally. They accept the sentence just as it is and can not see if the true meaning is the opposite of the literal meaning.
The language centre in the brain's left hemisphere is the first to interpret the literal meaning of words, then the frontal lobes and right hemisphere process the speaker's intention and check for contradictions between the literal meaning and the social and emotional context. Then finally, the right ventromedial prefrontal cortex, our sarcasm meter, makes a decision based on our social and emotional knowledge of the situation.
Experience of past situations is also very important and does perhaps explain the difference in the grasp of irony on either side of the Atlantic.
Dr Shamay-Tsoory says it is possibly a cultural difference as the English have a more complicated and subtle sarcasm that the Americans are used to.
The team suggests that there is a three-stage neural pathway in our brains that enables us to understand irony.
The research is published in the May issue of the journal Neuropsychology.