NOT for nothing do they call it the dark heart of cinema. Horror movies in all their pulse-quickening guises – supernatural chillers, slasher flicks, films about zombies, or witchcraft, or demons, or monsters – are enjoying what many industry observers believe is another golden age. The hugely popular FrightFest strand at the 2016 Glasgow Film Festival, which starts on Thursday, is proof of this; competition for seats in the three-day mini-festival gets fiercer with each passing year.

The FrightFest programme includes world, European and UK premieres of horror movies. It opens with The Forest, a supernatural horror set in Japan's most haunted location, which stars Natalie (Game Of Thrones) Dormer. Also being screened is The Wave, an epic action-thriller that had been a huge hit across Scandinavia.

A third movie, Baskin, is billed as a "terrifying and visceral tour-de-force" involving "subhuman cannibalistic freaks", while the closing film, The Devil's Candy, is described as a "bloody explosion of heavy metal, murder and mayhem".

Meantime, a huge buzz has been stirring in advance of the release of The Witch, about which literary horror-master Stephen King, recently tweeted: "The Witch scared the hell out of me. And it's a real movie, tense and thought-provoking as well as visceral." Actor and director Eli Roth says it’s the scariest movie he has seen in years. A headline in Rolling Stone magazine describes it as the "horror movie of the year". Set in 1630s New England, its stars include Kate Dickie, the Scots actor whose film CV includes Filth, Red Road and Prometheus.

All of this raises the spectre of an ages-old question: just what is it about horror films that keep so many film fans hooked?

So what is horror ... and why do we like to be scared?

The question is addressed by Marc Blake and Sara Bailey in their 2013 book, Writing The Horror Movie, which defines "horror" by quoting an academic definition, as "fear of some uncertain threat to existential nature and disgust over its potential aftermath". Stephen King is also quoted: horror, he has said, serves as a "barometer of those things which trouble the thoughts of a whole society". Even Aristotle is cited Aristotle too: according to the Greek philosopher, "horror in drama allowed the audience to purge itself of negative emotions through catharsis".

In essence, say Blake and Bailey, horror is the fear of the unknown.

"I suspect that horror films allow us to experience strong emotions such as fear, anxiety, and almost unbearable tension that, when broken, can shock us so much that we scream or jump," says Dr Caroline Watt, Koestler Senior Lecturer at the Koestler Parapsychology Unit at Edinburgh University. "But we know deep down we are safe because it is only a movie."

"Perhaps watching horror films also taps into the same kind of sensation-seeking that drives people to go on rollercoasters and ghost trains," she adds. "Afterwards, we are relieved but also exhilarated at the experience that we've had. I think there's also a social dimension. If we share these experiences with others, emotions are heightened, and afterwards it is fun and reassuring to laugh at the bits that scared us most."

So why do we love being scared by horror films? "I've asked this question so many times," says Alan Jones, one of the founders and curators of FrightFest, the 16-year-old company whose major annual events include the horror programme at the Glasgow Film Festival.

He adds: "I've actually synthesised it down to the fact that it is just a safe darkness. We all like being frightened, and there's so much around in the news in general, in our lives, that is facing us. The future will be scary.

"I just think that to be able to sit in a darkened room with like-minded people who all jump at the same time, and also shriek with laughter when they know that the threat has gone away – there's something comforting in that, and it's a shared experience. We share each other's fears and emotions."

Jones has previously acknowledged that horror fans are the most devoted of audiences. "If you thrill and/or shock them, they will be yours for ever," he said.

As to whether horror movies have become more inventive, he says that while some major studios follow the tried-and-tested formulae – "we're still seeing paranormal activities and monsters and exorcisms" – there is also a vibrant underbelly of horror filmmakers.

"They know the genre inside out, they're big fans and now, because they can go out and get a camera, there's a great democracy going on. If you have an idea, and want to put it on film, you can do it quite cheaply. If you do have a talent, you will rise to the top.”

Asked about our abiding fascination with horror films, Ryan Lambie, deputy editor at the UK website of Den Of Geek, who incidentally is heading to Glasgow for FrightFest, says: “It’s an interesting question. I think it goes back to old campfire tales and things like that. Probably the first tales we told each other, in man’s early history, were horror stories of one sort of another.

“Horror falls into different strands. You’ve got horror that’s about the physical fears of ageing, disease and injury and so on, and you’ve also got the spiritual side, about life after death – are there ghosts? What happens to us when we die?

“It’s a two-part thing. They deal with our mortal fears but also, in a weird sort of way, they provide comfort as well. When Stanley Kubrick made The Shining, he was ferociously atheist and didn’t believe in life after death. He said to Stephen King [who wrote the novel], ‘You’re an optimist – your ghost story is inherently optimistic because it assumes there’s life after death’.

“So even though you might be scared by a ghost story in the moment, there’s also that layer of comfort that death is not the end.”

Many horror movies have become notorious for what has been termed "torture porn". There seems to have been a cyclical trend in extreme horror movies, with some of today’s more outré offerings acting a kind of updated extension of some 1960s Hammer films. Even in the 1930s and 1940s, Lambie notes, there were some “pretty extreme” horror movies being made – a process that was halted for years by Hollywood’s Hays Code – the film industry moral guidelines applied to American films between 1930-1968. “As soon as that went away, [the extreme horror trend] came back in and you had films like The Exorcist, which really pushed the envelope at that time.”

Lambie feels that films “are becoming a lot more supernatural again and less ‘torture-porny’.” Certainly, The Witch, which went down a storm at last year’s Sundance Film Festival, is the finest traditions of old-fashioned, genuinely frightening films, the veritable stuff of nightmares.

Its director, Robert Eggers, has told how he realised he had to make a movie that was personal to him and did not involve him sacrificing his values.“So I was like, I’ve gotta go back to my past,” he told Vanity Fair. “I’ve gotta go back to New England and make an archetypal New England horror story. And it has to be witches, because they’re the archetypal New England ‘spook.’ They were really very much the stuff of my dreams as a kid – or my nightmares, I should say. I wanted to make a nightmare from the past – like a puritan’s nightmare come to life.”

Film lovers who have already watched The Witch have been tweeting their reactions, and they capture perfectly horror fans’ enjoyment of moments of terror. “The final 20 minutes of the film is the most tense cinematic experience I've had since seeing the original Exorcist! BRAVO!!,” enthused one. “The Witch is a film that really stays with you,” tweeted another. “Haunting, gothic horror. Tense and scary. I loved it.”

But if it's part of human nature to enjoy being spooked, one question remains. Why do we queue up to be terrified alongside hundreds of others in a crowded cinema? "A film festival at its heart is a celebration of the communal experience of watching films together," says Kirstin Innes, Press Manager at Glasgow Film Festival. "I think people like to be scared within a controlled environment, and I think that multiplies when we have a horror festival set-up as we have with FrightFest. Everyone is scared together in a communal environment and I think that's greatly appealing."

FrightFest Glasgow runs from February 25-27

www.frightfest.co.uk; glasgowfilm.org/festival