Edinburgh Castle is widely believed to be haunted

Their findings - if any - will be unveiled on 17 April, the final day of the Edinburgh International Science Festival.

However, Dr Richard Wiseman, a psychologist from the University of Hertfordshire, who is leading the investigation, admitted he was sceptical about the existence of ghosts.

He said: "I'm a sceptic but if I see a ghost walking through the wall, then I'm prepared to be converted.

"This investigation is to try to understand why people have ghostly experiences - it may be down to something simple such as walking into cold air."

'What better place?'

He added: "We decided to come to Edinburgh because it has an amazing reputation for being haunted. What better place to come if you want to carry out an investigation into ghosts?"

The "ghostbusters" will use a range of equipment, including a thermal imager, geomagnetic sensors, temperature probes and night vision devices, to monitor the locations.

More than 200 people will take part in the project by walking through the South Bridge vaults to indicate whether they experience unusual phenomena.

Last year, Dr Wiseman was the first scientist to be permitted to investigate reports of ghostly activity at London's Hampton Court Palace.

'No waste of time'

US psychologist James Houran, who has previously investigated the paranormal, said he was excited at what findings the new investigation could throw up.

Mr Houran, from Illinois University School of Medicine, said: "Whatever happens at the end of the investigation, our research will not have been a waste of time.

"I have had experiences in previous investigations such as hearing voices, phantom footsteps and equipment playing up, but I don't know if there were paranormal reasons for that or physical influences.

"People maybe are more inclined to believe in ghosts if they are in a dark, damp dungeon, but this research should give us more of an understanding of why people have ghostly experiences."

The science festival runs from Friday until 17 April.