Sarcasm may be the lowest form of wit, but Australian scientists are using it to diagnose dementia, according to research published on Friday.
Researchers at the University of New South Wales found that patients under the age of 65 suffering from frontotemporal dementia (FTD), the second most common form of dementia, cannot detect when someone is being sarcastic.
The study, described by its authors as groundbreaking, helps explain why patients with the condition behave the way they do and why, for example, they are unable to pick up their caregivers' moods, the research showed.
"This is significant because if care-givers are angry, sad or depressed, the patient won't pick this up. It is often very upsetting for family members," said John Hodges, the senior author of the paper published in "Brain".
"(FTD) patients present changes in personality and behaviour. They find it difficult to interact with people, they don't pick up on social cues, they lack empathy, they make bad judgements," he told AFP.
"People with FTD become very gullible and they often part with large amounts of money," he said, adding that one in 4,000 people around the world are afflicted with the condition.
Researchers began studying the role of sarcasm in detecting FTD because it requires a patient to spot discrepancies between a person's words and the tone of their voice, Hodges said.
"One of the things about FTD patients is that they don't detect humour - they are very bad at double meaning and a lot of humour (other than sarcasm) is based on double meaning," he said.
The research, conducted in 2006-07, put 26 sufferers of FTD and 19 Alzheimer's patients through a test in which actors acted out different scenarios using exactly the same words.
While in one scenario, the actors would deliver the lines sincerely, in others they would introduce a thick layer of sarcasm. Patients were then asked if they got the joke, Hodges said.
For example, said Hodges, if a couple were discussing a weekend away and the wife suggested bringing her mother, the husband might say: "Well, that's great, you know how much I like your mother, that will really make it a great weekend."
When the same words were delivered sarcastically and then in a neutral tone, the joke was lost on FTD patients, while the Alzheimer's patients got it.
"The patients with FTD are very literal and they take what is being said as genuine and sincere," said Hodges.
FTD, often referred to as Pick's disease, is similar to Alzheimer's in that it involves a progressive decline in mental powers over a number of years, but FTD affects different regions of the brain.
"It can be very difficult to diagnose in early stages and to separate from depression or, later on, schizophrenia or personality disorders," Hodges said.
The sarcasm test could replace some more expensive and less widely available tests for dementia, he said.
When questioned about the applicability of the test to people from countries not renowned for their appreciation of sarcasm or irony, Hodges said the test could be modified.