"What was the price did Santa's sleigh cost? Zero, it was on the house."
This quip is greeted with groans that echo through a warehouse in the capital.
This describes a joke-testing meeting with a company that makes supplies for social events. Its repertoire includes Christmas crackers.
The firm's founder grins, nearly sheepishly at the gag. But the pun has made the cut and will appear in future crackers.
"You measure the gag by the number of moans and the intensity of the groans around the table," the founder explains.
The secret to a great Christmas cracker pun is not the identical as a stand-up joke in itself. It is entirely about the setting - in this case, the shared laughter of the holiday dinner table with elders, children and potentially neighbours.
"The goal is for the joke to be a thing that unites the child in harmony with the 80-year-old," she adds.
Gathering to experience shared amusement is not only ancient, scientists say, it is likely to be older than humanity.
"So when you are laughing with people at the holiday table you are dropping into what's very likely a truly ancient mammalian play vocalisation," says a neuroscience expert.
Communal amusement, she explains, helps make and maintain social connections between people.
Researchers have found that a absence of these social exchanges can seriously harm mental and physical health.
"The people you converse with, and laugh with, it leads to enhanced amounts of 'happy chemical' release," she adds.
Endorphins are the body's "happy chemicals" and are released both to reduce stress and pain and in reaction to enjoyable experiences, such as chuckling with loved ones over a particularly awful festive cracker joke.
"It's not simply laughing at a silly joke with a holiday cracker," the expert says. "You are in fact performing a lot of the really important work of building, preserving the connections you have with the people you care about."
But what is actually happening within the brain when we listen to a gag?
A tremendous amount occurs in reaction to comedy, it turns out.
Employing functional magnetic resonance imaging (fMRI), a kind of neural imager which shows which areas of the mind are more active, scientists have been able to map the regions that receive more blood flow.
Testing entails imaging the brains of volunteer participants and then subjecting them to a database of funny words, paired with either a neutral sound, or pre-recorded chuckles.
"In the scanner we got a really fascinating pattern of activation," says the neuroscientist.
A gag stimulates not just the parts of the mind in charge of hearing and understanding speech, but also brain regions involved in both preparation and starting movement and those linked to vision and memory.
Combine all of this together, and individuals listening to a joke have a sophisticated series of brain reactions that support the amusement we experience.
Scientists found that when a funny word is combined with chuckles there is a stronger response in the mind than the identical phrase when accompanied by a neutral sound.
"This was in areas of the brain that you would employ to contort your face into a smile or a laugh," the professor says.
It indicates people are not just responding to funny jokes, they are responding to the amusement that follows them.
Amusement, says the expert, can be contagious.
So what does this imply for the laughter found around a Christmas table?
"People laugh harder when you are familiar with people," she notes, "and laughter increases more when you like them or care for them."
When it comes to Christmas cracker jokes, she says, the feel-good factor is more likely to be triggered not by the gag itself, but from the reaction to it.
"It's the laughter. The joke is the dreadful Christmas cracker joke, and it's just a pretext to laugh as a group."
Will we ever find the perfect joke?
Probably not, but that has not prevented experts from attempting to.
Years ago, a professor set up a scientific project for the world's most humorous gag.
Over 40,000 jokes later, with ratings lodged by hundreds of thousands of participants globally, he has a clearer understanding than many as to what works and what does not.
The ideal Christmas cracker pun must be brief, he says.
"They must also be poor jokes, jokes that cause us to moan," he continues.
The increasingly "awful" the gag, he states the better.
"The reason is that if no-one finds it funny – it's the joke's shortcoming, not your own.
"What's interesting about the Christmas cracker jokes is that none of us find them humorous.
"It creates a common experience around the gathering and I think it's wonderful."
A seasoned software engineer with a passion for open-source projects and tech education.
