Ghosts in the Machine - with picture slideshow

The project – undertaken as part of the Edinburgh International Science Festival and profiled exclusively in The Scotsman on 10 March – invited people to send in ghostly photographs for analysis and, once they were put up online, asked web users to vote as to whether or not they believed they were the real deal.

To date, the site has received 250 photographs and more than 250,000 votes.

While many of the images can be easily discredited, even Wiseman is finding it particularly tricky to disprove one – the spooky face of a woman at a window at Tantallon Castle in East Lothian. The image came out top in the experiment, with nearly 40 per cent of online voters believing that the photograph shows a bona-fide ghost.

"The study has been a huge success," says Wiseman. "The sheer number of people who've got involved shows just how much interest there is in ghosts. We've been amazed to find that, even when an image obviously just shows the camera flash reflecting against a surface, around 10 per cent of people still believe it's a ghost."

A high number of the supposedly ghostly images can be given a simple explanation. What look like mysterious lights, mists and orbs can, in reality, be anything from a camera flash reflecting off dust particles to condensed human breath in front of the lens. However, the Tantallon Castle image has even the logical Wiseman stumped. "It's a tough one," he says. "This experiment has been a big success, not only because we've had so many responses, but because we've come across this one very curious image that we simply can't explain."

Here, we take a closer look at the five images that had the highest number of online voters convinced that something spooky was indeed afoot.