"How much did Father Christmas's sleigh cost? Nothing, it was on the house."
This one-liner is met by moans that echo through a storage facility in London.
This describes a humor-evaluation session with a firm that produces products for social events. Its repertoire features festive crackers.
The firm's founder smiles, almost sheepishly at the joke. But the joke has been selected and will feature in upcoming crackers.
"You measure the joke by the volume of moans and the intensity of the groans at the table," the founder says.
The secret to a great holiday cracker pun is not the identical as a stand-up gag per se. It is entirely about the context - in this case, the shared laughter of the holiday meal with elders, children and possibly neighbours.
"You want the gag to be something that brings the child together with the 80-year-old," she adds.
The Neuroscience Of Communal Laughter
Gathering to experience communal laughter is not only ancient, experts say, it is probably to be older than humanity.
"So when you are chuckling with others around the holiday dinner you are dropping into what's very likely a truly primordial mammal social sound," says a neuroscience expert.
Communal laughter, she says, helps make and maintain social bonds between individuals.
Scientists have found that a lack of these social exchanges can significantly damage both psychological and bodily health.
"Those you talk to, and laugh with, it results in enhanced amounts of endorphin uptake," she continues.
Endorphins are the brain's "feel-good compounds" and are produced both to alleviate stress and pain and in response to pleasurable activities, such as laughing with friends over a truly awful festive cracker joke.
"It's not simply chuckling at a silly joke with a holiday cracker," the expert states. "You are in fact performing a lot of the truly vital work of building, preserving the connections you have with the people you love."
What Occurs Inside the Brain?
But what is truly happening inside the mind when we hear a gag?
An awful lot occurs in reaction to comedy, it transpires.
Using functional magnetic resonance imaging (fMRI), a kind of neural imager which shows which parts of the brain are more active, scientists have been able to map the regions that get more blood.
Testing involves scanning the brains of healthy participants and then subjecting them to a collection of humorous words, accompanied by either a neutral sound, or pre-recorded laughter.
"During the study we observed a really fascinating activation pattern of neural activity," notes the neuroscientist.
A gag activates not just the parts of the mind responsible for hearing and interpreting speech, but also neural areas associated with both planning and starting motion and those linked to vision and recall.
Combine these elements together, and people hearing a joke have a complex series of neural reactions that underpin the laughter we experience.
The Infectious Nature of Laughter
Scientists discovered that when a funny word is combined with chuckles there is a greater reaction in the mind than the same phrase when followed by a neutral sound.
"This activation occurred in areas of the mind that you would use to contort your face into a grin or a chuckle," she explains.
It means people are not just responding to humorous words, they are responding to the laughter that follows them.
Amusement, according to the expert, can be contagious.
So what does this mean for the laughter found at a Christmas table?
"You laugh harder when you are familiar with others," she says, "and you laugh further when you are fond of them or care for them."
When it comes to Christmas cracker jokes, she says, the feel-good effect is more probable to be caused not by the gag in itself, but from the response to it.
"It's the laughter. The gag is the terrible Christmas cracker pun, and it's just a reason to chuckle together."
The Search for the Ideal Cracker Joke
Will we ever find the perfect gag?
Probably not, but that has not prevented researchers from attempting to.
Years ago, a professor established a scientific project for the world's most humorous joke.
Over 40,000 gags submitted, with scores provided by 350,000 participants around the world, he has a better understanding than most as to what succeeds and what fails.
The perfect festive cracker pun needs to be short, he says.
"They must also need to be bad gags, puns that cause us to groan," he adds.
The more "terrible" the joke, he states the more effective.
"The reason is that if no-one laughs – it's the gag's fault, not yours.
"What's interesting about the Christmas cracker puns is that none of us find them humorous.
"It creates a common experience at the gathering and I think it's wonderful."
