Everybody experiences it sooner or later: that disconcerting moment on holiday when the stranger on the neighbouring sun lounger turns out to be the daughter of your primary school headmistress, or the man who used to fix your boiler. It is the reason so few of us dare use naturist beaches, even on the other side of the world. So do not be too nonplussed in the coming month if a friend or acquaintance hands you a giant jigsaw piece and asks you if you know a Glaswegian architect called Allistair.

You are part of a global experiment. The “six degrees of separation” — the theory that everyone on the planet is linked to everyone else by no more than six personal links — has been fascinating sociologists and dinner-party conversationalists since the late 1960s. It holds that even if you’ve never met any architects, Glaswegians or anybody called Allistair, the chances are you probably know someone who has — or someone who knows someone who has. It ’s a small world, and the artistic duo Hole in My Pocket are determined to show just how small.

“Everybody and everything is connected in one way or another,” claims Allistair Burt, the 26-year-old Glaswegian who is sending out 54 giant jigsaw pieces to randomly selected people with the help of fellow architect Scott Airlie. “This experiment is just a way to try and prove it on a global scale.”

Their project is based on a similar test by Stanley Milgram, the American social psychologist, who sent 96 packages to random people in Kansas and Nebraska and discovered that most could find and return them to a Boston stockbroker by means of less than five intermediaries.

His resulting 1967 theory of the six degrees of separation has since spawned a stage play, film and countless spin-offs including a peculiarly addictive parlour game known as the Six Degrees of Kevin Bacon. (Bacon links with Charlie Chaplin in three steps: via his role in Mystic River with Laurence Fishburne, who was in Apocalypse Now with Marlon Brando, who appeared with Chaplin in A Countess from Hong Kong.) However, Milgram never tested his theory outside America.

This is why Burt and Airlie are going global. As of this week, pieces of their foam-backed jigsaw of the world will be spreading to 54 people in dozens of countries, each requested to pass it on to anyone they know who might help it get a little closer to its target — identified only by his name, city and occupation. With the aid of postcards sent by recipients at each stage of the journey, the two men will track the jigsaw’s progress and gradual reassembly on a central website.

The internet didn’t exist in Milgram’s day which is a sore point. Now it’s as easy as a click on Google to find Burt’s address and send the package straight back without bothering with the five intermediaries at all. “That’s why we’re insisting people pass the package only to people they know,” he stresses.

“We chose a jigsaw because this is an attempt to show how people fit together,” says 25-year-old Airlie. “We’re always hearing about war and terrorism and what divides us. This should highlight how close we really are to those around us.”

Appropriately, even their friendship is entirely coincidental — beginning when the alphabetic proximity of their surnames gave them adjacent desks at Strathclyde University — and they’ve experimented with their shared obsession for chance connections ever since.

They attracted most attention (and an award from Glasgow’s Lighthouse architecture and design centre) when they left 50 anonymous weather-proof notebooks in public places around the world. Inscribed with the words “Read Me”, the mobile message boards accumulated stories ranging from the travails of a homeless man to a celebratory cartoon from a newly-engaged woman.

“Some people told us folk would just dump the books, or burn them,” says Burt. “But they’re still travelling around with a life of their own. I believe people give themselves to these things. One of the first guys who ever contacted us about the book was a cleaner who found it on the Glasgow underground, and said we inspired him to go out and buy a pack of pencils. That’s why we were doing it. It made us realise you could touch strangers’ lives in unusual ways.”

The idea led on to the current project, further exploring the links between strangers. Artists are not the only ones intrigued by small-world theory. According to sociologists, the spread of ideas, viruses or jigsaw pieces relies on a combination of strong networks (family, close friends, people we see every day) interlaced with weaker links (old friends, more sporadic contacts) who take us out of our own cliques and give access to other people’s.

Jung staked his reputation on his theory of synchronicity — that our thoughts influenced actual events — but Burt and Airlie are keeping an open mind on whether pure chance or something more mysterious will bring their jigsaw pieces home.

“I think there is another dimension — whether you call it God or some other kind of energy at work,” grins Airlie. “But I’m not sure I’m smart enough to work out what it is.”

Airlie and Burt are dispatching the jigsaw during their exhibition at the Arches, Glasgow, running until May 26. Visit www.holeinmypocket.com

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