Old people can still enjoy a good laugh - but only if the joke is obvious, a study suggests.
The findings apply to people with a sense of humour in the first place
Researchers in Canada have found that a person's sense of humour remains intact when they grow old.
However, they have found that the ability to understand more complex jokes can deteriorate with age.
Writing in the Journal of the International Neuropsychological Society, the researchers suggested ageing of the brain is to blame.
Dr Prathiba Shammi and colleagues at the Baycrest Centre for Geriatric Care in Toronto have previously identified the part of the brain associated with humour, namely the right frontal lobe.
They also showed that people with damage in this area of the brain, from a stroke for instance, were less able to appreciate punch lines and preferred slapstick humour.
In this latest study, they sought to find out if growing old also affected a person's sense of humour.
They carried out tests on 20 older adults, with an average age of 73, and 17 younger adults, with an average age of 28.
They were all asked to complete three separate humour tests.
In the first test, they were presented with 28 statements and asked to identify the humorous ones. Three out of four were humorous. They included:
Sign in a tailor shop: "Please have a fit upstairs"; and
Sign in a hotel: "Please take advantage of the chambermaid"
In the second test, they were asked to select the correct punchline from four options for 16 incomplete jokes. For instance, the first part of one joke read:
"The neighbour approached Mr Smith at noon on Sunday and inquired 'Say Smith, are you using your lawnmower this afternoon?' 'Yes, I am,' Smith replied warily."
Those involved in the study then had to choose from one of four options. "Then the neighbour answered:
(A) 'Fine, you won't be wanting your golf clubs, I'll just borrow them'; or
(B) 'Oops!' as the rake he walked on barely missed his face; or
(C) 'Oh well, can I borrow it when you're done then?; or
(D) 'The birds are always eating my grass seed.'
The correct or humorous answer in this case was A.
In the third test, participants looked at 10 different cartoon drawings. Each cartoon consisted of a series of four similar drawings only one of which had a funny detail. Participants were asked to select the correct one.
The researchers found that old people performed just as well as younger adults in the first test. However, they made significantly more errors in the other two.
The researchers also tested the older adults' cognitive abilities, such as their memory and abstract reasoning.
They found that people who scored low in these tests were also most likely to do badly in the humour tests.
"The good news is that ageing does not affect emotional responses to humour," said Dr Shammi. "We will still enjoy a good laugh when we get the joke.
He said the discovery that a person can keep their sense of humour when they grow older is important.
"It is integral to social interaction and it has long been postulated that humour may enhance quality of life, assist in stress management, and help us cope with the stresses of aging," he said.