Sarcasm might be the lowest form of wit but something's amiss if you can't detect it, according to UNSW researchers.

Patients with a particular type of dementia often can't pick up when someone is being sarcastic, according to a paper which has been published in the journal Brain.

The study's result could be used to help provide an early diagnosis for the behavioural form of frontotemporal dementia (FTD) and to help manage the condition. It may be particularly useful in determining which patients will deteriorate rapidly.

FTD is the second most common form of dementia in people under 65, yet it is frequently misdiagnosed. It may also be much more common in those who are over 65 than is currently believed.

Australia is estimated to have up to 5,000 people with FTD - many of whom do not know they have the condition.

"People with FTD become very gullible and they often part with large amounts of money," said the senior author of the paper, UNSW Professor John Hodges, who is based at the Prince of Wales Medical Research Institute. "This research goes towards explaining why they behave the way they do. They are not able to pick up the subtilties of communication."

Through video technology, the researchers also showed the patients performed poorly when reading negative emotions.

"This is significant because if care-givers are angry, sad or depressed, the patient won't pick this up," said Professor Hodges. "It is often very upsetting for family members. We hope this work will help them understand what is going on."

The researchers showed these changes in emotion correlated to brain shrinkage in three closely integrated brain regions.

Media Contact: Susi Hamilton | 9385 1583 | 0422 934 024 | susi.hamilton@unsw.edu.au