What do Christmas cracker jokes do to our brains?

“How much did Santa’s sleigh cost? Nothing, it was on the house.”

The joke is met with groans echoing through a warehouse in Lambeth, London.

We’re in a prank testing session with Talking Tables, a London company that produces materials for meetings. His repertoire includes Christmas crackers.

Clare Harris, the firm’s founder and chief executive, grins almost apologetically at the joke. However, the joke made the cut and will feature in future crackers.

“You measure humor by the number of moans and the volume of moans around the table,” Ms. Harris says.

The key to a good Christmas cracker joke is not the same as a good joke per se. It’s all about context; in this case, laughter shared at the Christmas dinner table with grandparents, children, and possibly neighbors or friends in attendance this year.

“You want the joke to be something that will bring the eight-year-old and the 80-year-old together,” Ms. Harris says.

Prank selection takes place upstairs in the warehouse, where a handful of staff from across the company gather to pitch and evaluate the latest jokes.

The jokes being worked on today will be the last few jokes to be made into crackers in 2026.

The company works at least a year in advance for the next batch of crackers.

“What do monkeys sing at Christmas?” asks Ms. Harris. “Forest bells, forest bells.”

This time there are more emphatic “no’s” than moans, and this time Ms. Harris admits defeat. It will not be available in any crackers next year.

“We have a database,” he says. “But we make sure we pack our home favorites every year.”

Cracker joke materials come from a variety of sources, including the internet, word of mouth, and the company’s own joke books.

Asked whether they have yet succumbed to the allure of artificial intelligence, Ms. Harris responds with flat denial.

The goal of the session, he says, is to figure out what his favorites are and which one evokes the greatest emotional response.

“Does it do what we want at the Christmas table?” he asks.

Chloe Lloyd from sales tells a joke she heard earlier that day.

“What does Ay do when her hair needs to be cut?” he asks. “Eclipse!”

The group says it was an instant success.

Experts say gathering together to enjoy shared laughter is nothing new, but probably a pre-human phenomenon.

“So as you’re laughing around the Christmas table with people, you stumble upon what is almost certainly a really old mammal game call,” says Prof Sophie Scott, director of the Institute for Cognitive Neuroscience at University College London.

He says shared laughter helps establish and maintain social bonds between people.

Researchers found: Lack of such interactions can seriously harm mental and physical health.

“People you talk to and laugh with leads to increased endorphin uptake,” says Prof Scott.

Endorphins are the brain’s “happy chemicals” and are released both to relieve stress and pain and in response to pleasurable experiences, like laughing with friends over a truly awful Christmas cracker joke.

“You don’t just laugh at a silly joke with a Christmas cracker,” says Prof Scott. “You are actually doing a very important job of maintaining social connections with your loved ones.”

And it’s not just people laughing.

Professor Scott says laughter is an invitation to play and form social connections. Rats and some other mammals also do this.

So what actually happens in our brains when we hear a joke?

It turns out that a lot of things happen in the face of humor.

Using functional magnetic resonance imaging (fMRI), a type of brain scanner that shows which parts of the brain are working harder, Prof Scott and his team were able to map the areas that receive more blood.

The test involves scanning the brains of healthy participants and then subjecting them to a database of funny words accompanied by a neutral “crunch” noise or pre-recorded laughter, then examining which parts of the brain work the most.

“We came across a really interesting activation pattern in the browser,” says Prof Scott.

Joking activates not only the parts of the brain responsible for hearing and interpreting speech, but also brain regions involved in both planning and initiating movement, and areas involved in vision and memory.

Putting it all together, Prof Scott says, people who hear a joke have a complex set of neural responses that underpin the laughter we hear; Not only do they listen to and understand the joke, they also prepare the motor functions needed to prepare to laugh, ensuring that their reactions are influenced by the images in memory.

Researchers discovered that when a funny word was paired with laughter, it produced a greater response in the brain than when the same word was followed by a neutral sound.

“This was in the parts of your brain you would use to turn your face into a smile or laughter,” says Prof Scott.

This means that people respond not just to funny quotes or jokes, but also to the laughter that accompanies them.

Laughter, says Prof Scott, can be contagious.

So what does this mean for laughter around the Christmas table?

“You laugh more when you know people, you laugh more when you like or like them,” says Prof Scott.

When it comes to Christmas cracker jokes, he says, the feel-good factor is more likely to come from the reaction to it, not the joke itself.

“It’s laughter. It’s a joke, it’s a terrible Christmas cracker joke, and it’s just a reason to laugh together.”

Will we discover the perfect joke?

Probably not, but that hasn’t stopped experts from trying it out.

In 2001 Prof Richard Wiseman from the University of Hertfordshire at Hatfield founded LaughLab, which researched the world’s funniest joke.

More than 40,000 jokes later, with ratings given to these jokes by 350,000 people worldwide, Prof Wiseman has a better idea than most of what works and what doesn’t.

He says the perfect Christmas cracker joke should be short.

“But they also have to be bad jokes, jokes that make us groan,” adds Prof Wiseman.

The “terrible” the joke, the better, he says.

“Because if no one laughs, it’s the joke’s fault, not yours.

“The interesting thing about Christmas cracker jokes is that none of us find them funny.

“It’s a shared experience around the table, and I think it’s lovely.”