Richard Wiseman, who led the study of an underground network of streets beneath the city’s Royal Mile, admitted: “Something quite odd was going on.”

But he does not believe that any of the experiences — which affected most of 200 volunteers — were paranormal. He is convinced that hauntings are caused by a combination of environmental and psychological factors.

The investigation focused on Mary King’s Close — a warren of streets sealed off from the outside world more than 200 years ago. Today the site is maze of dark narrow alleys and the remains of houses.

Mary King’s Close became entombed when Edinburgh’s Royal Exchange — now the City Chambers — was built in 1753. The top floors of the houses were demolished and the lower floors incorporated into the new foundations.

The rooms of many houses still exist, and according to some reports, so do a number of their former residents.

Professor Wisemen sent groups of volunteers to four locations without telling them that only two had a strong reputation for being haunted. The aim was to compare reports from the different sites.

About 70 per cent of those visiting the haunted locations reported unusual phenomena. In contrast, only 48 per cent of people exploring the locations not reputed to be haunted had spooky experiences.

At the most haunted site, where a sinister figure in black has been seen repeatedly, something strange happened to more than 80 per cent of the volunteers.

“There was a massive difference between the locations,” said Professor Wiseman, from the University of Hertfordshire. “Sometimes people just felt very cold, but there were some quite extreme experiences — feelings of being watched, being touched and having clothing pulled, apparitions of people and animals, and footsteps. I was really surprised at the extent of the experiences.”

Probably the strangest report was from a volunteer who complained about being stared at by a member of Professor Wiseman’s team from the end of a corridor. No one was there.

Experiments showed that the two “haunted” locations were significantly less humid than the other sites. This can generate a feeling of coldness, Professor Wiseman said.

There was also evidence of “infrasound” — low frequency sound waves that are too deep for the human ear to pick up, but are known to produce feelings of unease. In the most haunted site there was a continuous infrasound rumble, possibly caused by overhead traffic.

A psychological test found that people rated photographs of the haunted locations as significantly more “ghostly” than those of the other sites. This suggested subtle visual features, such as shape, lighting, or the presence of doorways, may be eliciting a sense of fear.

Professor Wiseman said: “It could be that the ghosts were down there, but I think the explanation is primarily psychological.” He said the findings might shed light on “sick building” syndrome — unexplained feelings of uneasiness or sickness associated with certain buildings.

The results will be submit- ted to the British Journal of Psychology.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Olympic-size television coming to your town
• Mosley opens new front in battle for privacy
• Decorator fined for smoking in van