Scientists say sarcasm, sometimes referred to as the lowest form of wit, might be a useful tool in diagnosing a certain type of dementia.
The researchers from the University of New South Wales (UNSW) say patients with frontotemporal dementia (FTD) or Pick's disease, have trouble reading emotions and are often unable to sense when someone is being sarcastic.
Being unable to pick up when caregivers are angry, sad or depressed, can be upsetting for those involved and sometimes makes managing such patients a difficult task.
Even though FTD is the second most common form of dementia in younger people (i.e. under 65) it is often misdiagnosed as a personality disorder or sufferers are dismissed as strange, and often ostracised because FTD can lead to sexual disinhibition, rudeness and a lack of empathy.
Experts estimate as many as 5,000 Australians suffer from the degenerative condition which many do not know they have - there is also the suspicion that FTD may be more common in those over 65 than is currently believed.
According to the UNSW researchers their study could be used to help provide an early diagnosis for the behavioural form of FTD and to help manage the condition and also be particularly useful in determining which patients will deteriorate rapidly.
According to the study's senior author Professor John Hodges, from the Prince of Wales Medical Research Institute, people with FTD become very gullible and often part with large amounts of money sometimes through gambling or because they trust other people more easily and lose judgement about their future.
The study helps explains that they behave the way they do because they are not able to pick up the subtleties of communication.
FTD is often very difficult to diagnose because people present with changes in personality and behaviour and Professor Hodges says care givers and relatives often report that people with the disease are generally humourless or without irony and he says comedy has to come into health care.
The study included the use of video technology which showed FTD patients performed poorly when reading negative emotions and Dr Hodges, a Professor of cognitive neurology, says this is significant because if care-givers are angry, sad or depressed, such patients will not pick this up, which is often very upsetting for family members.
The researchers devised a simple and non-invasive test where patients are merely asked: do you get the joke?
Actors perform short scenarios always using exactly the same words - in some of the scenarios they are sincere and genuine and in other scenarios they are being sarcastic.
Professor Hodges says the test showed that people with FTD are very literal because the differences were all about tone of voice, mannerisms and subtle social cues - when the test was tried on Alzheimer's patients, they had no trouble with it and recognised the sarcasm.
The researchers showed these changes in emotion correlated to brain shrinkage in three closely integrated brain regions and Professor Hodges says all the findings were consistent with shrinkage of the amygdala - an area on the right side of the brain which controls a person's mental and emotional state.
The study is published in the journal Brain.