Grumpy old men may not be able to help it, as age could affect their sense of humour, scientists have found.
People aged over 65 may find it harder to understand jokes
A study by Washington University in St Louis found older people find it harder than students do to understand jokes.
The authors say the finding should be taken seriously as laughing has been linked to health benefits such as boosting circulation.
The findings were published in the Journal of the International Neuropsychological Society.
The researchers tested 40 people aged over 65, and 40 undergraduates.
The participants had to complete jokes and cartoon strips, choosing the correct punchline or final picture from a selection of options.
Choosing the punchline for jokes, undergraduates performed 6% better than older people, and completing cartoon strips they were 14% better.
One such joke in the test was: "A businessman is riding the subway after a hard day at the office. A young man sits down next to him and says, 'Call me a doctor, call me a doctor'. The businessman asks, 'What's the matter, are you sick?'.
The participants were expected to correctly identify the punch line as: "The young man says, 'I just graduated from medical school'."
The report's authors said the results suggested that age-related declines in short-term memory, abstract reasoning and moving between different thought trains may affect humour comprehension in older people.
Author Professor Brian Carpenter said: "This wasn't a study about what people find funny. It was a study about whether they get what's supposed to be funny.
"There are basic cognitive mechanisms to understanding what's going on in a joke.
"Older adults, because they may have deficits in some of those cognitive areas, may have a harder time understanding what a joke is about."
Dr Chris Moulin, a cognitive neuropsychologist at the University of Leeds said it was "entirely feasible" that people's understanding of jokes could change with age.
He said: "Many jokes require us to simultaneously have two ideas in mind, such as two meanings of the word 'call' in the example joke, and older people may find it difficult to do this."
And he said having a sense of humour was important to health because laughter can maintain wellbeing by boosting levels of so-called "happy hormones."
But he warned that if the jokes used in the study used modern humour, then the younger people might find them funnier and understand them better anyway which would affect the results.
I trade jokes with people my own age because of our shared experiences. I also share my daughters sense of humour, (and she is nineteen), so we can laugh at the same things. Yet, my two sons, both of whom are in their mid-twenties, seem to have a sense of humour that breaches any understanding on my part. I don't believe there is a generational gap so much as a perspective at play.
W. Hemmings, Calgary, Canada
I don't understand anything anymore. Just go with the flow and pretend to, laughing uproariously at all the wrong moments.
Peter Bradshaw, Tadcaster, UK
I think you would have to have to be incredibly immature to find such a joke even vaguely funny. Ths study consequently reflects the greater intelligence of the older participants.
Eliazabeth James, London
I don't find it more difficult to understand jokes now that I am 42. I just find that contemporary comedy is dull. I have a great sense of humour and draw cartoons for a local paper. I'm still looked at as a grumpy old man though; it has nothing to do with comedy at all!
Simon Edwards, Market Harborough, UK
It's entirely possible that after a lifetime of experience older people may be less inclined to laugh. They may get the joke all too well.
David B. Wright, Wellfleet, MA,USA
The punchline is "I just graduated from medical school"? That's pathetic. Maybe, someone should do a study as to whether researchers actually have a sense of humor.
Simon, Pasadena, CA
I am over 60. I am just as quick-witted as I ever was - but I simply don't find some of the the things that are supposed to be funny to be funny anymore. In other words, I have matured. My sense of humour is no longer puerile, but a lot more subtle. Sorry, I am not slower on the uptake!
Anthony Owen, Monmouth, UK
My paternal grandfather is over 70 and has a sense of humor infamous in its ability to make people groan with annoyance. His material revolves around singing crude Irish songs badly and reciting limericks. He is nearly senile in all other respects, but his cognitive abilities in humor seem to be undeterred... unfortunately.
Emily, Treichlers, PA, USA
I can completely agree, I turned 38 yesterday and given the fact I already look about 55, a lot of the people I know have said that I'm noticeably slower witted and regularly grunpy for no reason.
Niall Murray, London
I get the "joke" in the example, but it is not funny. I think the researchers are the ones lacking humour.
Isus Krist, Isusje, Croatia
It's hard to laugh at jokes you have heard a thousand times before - the older you get the more chance you've already heard it!
Joyce, London, England
I'm as quick-witted as ever, perhaps more so, than I was fifty odd years ago, but I would probably claim that anyway. The only problem, according to my children, is that I am getting repetitive, and that they would like to hear something original for once.
Raymond Hopkins, Kronoby, Finland