Eli Roth, producer of The Last Exorcism Part II, believes he knows the secret of the genre's longevity.
"Horror movies are the best date films. It is the only time you are absolutely guaranteed to be squeezing your date's arm, and if the film really works, no-one ever wants to sleep alone after it's over."
Having the creator of the controversial Hostel films – movies accused of introducing "torture porn" to cinema – pronounce on cinematic romance might seem surprising, but Roth, writer and director as well as producer, is a versatile kind of guy. He even has his own haunted house attraction in Las Vegas, The Goretorium. In case you are wondering, yes, it also hosts weddings.
We'll move on to torture porn later. What is not in doubt for now is Roth's reputation as a bankable name.
His first film, 2003's Cabin Fever, returned a mountain of cash after being made for a hill of beans (production budget: $1.5 million; total earnings: $100m). The first instalment of The Last Exorcism achieved a similar feat. The new film, out next week, revisits heroine Nell Sweetzer as she attempts to reassemble her life after the shocking events of the first movie.
"I never want to give away the secrets inside the haunted house, but now that we know who and what we're dealing with, we really get to explore that," says Roth.
We meet in Glasgow ahead of the premiere of Aftershock, a horror set in Chile during the 2010 earthquake. At the Glasgow Film Theatre later, Roth is greeted with only marginally less warmth than Rod Stewart, with the reception growing even toastier when the natural mimic tells a story complete with a pretty decent Scots accent. Told you he was versatile.
Here in a basement room at the Blythswood Hotel it's a quieter, more thoughtful Roth holding court. Aftershock delves into the collapse of society after a disaster, an idea which intrigues the 41-year-old.
"I've heard that humans are nine meals from anarchy; that if we don't get food nine meals in a row people will start killing their neighbours. People go right back to this feral state of survival, protecting what is theirs. That has always fascinated and terrified me, that it could happen that easily."
It is when people are pushed to the edge that their true personalities come out, he says. How would he cope?
"I'd love to think I would be brave and heroic. Everybody wants to think of themselves as the hero, nobody wants to think of themselves as the coward that would survive for themselves, but I'm sure there's a part of all of us that would at a certain point."
Roth, the Boston-born son of a psychiatrist and a painter, has come close to the edge himself a couple of times. Out mountain climbing one 4th of July, his party was caught in an electrical storm. "We had to go down through the storm cloud, through lightning bolts every five seconds, to get out of it. Three people in a neighbouring party were killed."
Then there was the time he was kayaking in Mexico and the canoe started to sink. He was pulled under but managed to get to the surface and help his friends, sea urchin spikes sticking into every part of him. Did he scream like a girl?
"I screamed after. I tend to shut it out when the adrenaline kicks in. It's afterwards you feel terrified and you realise how close you came to dying."
Mention of screaming brings us to the Hostel films, where the agonised cries of unfortunate backpackers form a hellish soundtrack. The films made money, but they also had many critics hitting the thesaurus for new ways to say nasty.
In response, Roth has said that the films, released in the wake of the Abu Ghraib prisoner abuse scandals, were a statement on torture. I'm curious, however, as to what that statement might be. Surely it is no secret that torture is heinous and corrupting.
"That's for the film scholars to find out," he says when asked to outline what the statement was. "I'm contacted every day on Twitter by students who are using Hostel for their theses. Not just film students, there are kids in ethics classes, philosophy classes. Colleges and universities are teaching the Hostel movie now. Critics can say whatever they want but seven years after the fact, that movie is still very potent and still very discussed [as representing] a particular time in America and American politics. That's what the best horror movies have, that layer of politics underneath."
But what was the political statement? "There were many political statements in Hostel. I could talk to you for two weeks about what was in Hostel."
What was the main one? "It's not for me to define. There are a lot of main ones. People come to their own conclusions about what's in the film."
In the best traditions of the horror world's undead, I come back for one last swing. If he was asked to justify showing torture, what would he say?
"I'd say that as a filmmaker I can tell whatever story I want. I don't have to justify anything to anyone. It's not being forced upon anyone. If they want to watch it they can watch it. It's not real torture. It's a depiction of torture. It's a story, it's fake, it's characters. I'm not pretending it isn't."
Hostel was produced by Roth's friend Quentin Tarantino, who subsequently cast Roth in the war drama Inglourious Basterds with Brad Pitt and Christoph Waltz. It was a landmark movie for Roth the actor.
"One of my favourite actors and filmmakers is Jodie Foster. I remember when she went back to school to study after she had been a successful actress. I thought that was a very interesting, bold move, yet she came out of it even better. That's what I wanted to do with [Inglourious Basterds]."
He stopped all other work and immersed himself in the part of Sergeant Donny Donowitz, Nazi-killer extraordinaire. Surrounded by "the best actors in the world, the best director in the world", he learned a lot.
Speaking of Tarantino, when they hang out together is it all classical music and playing chess? "We can, we have. It depends what we're doing. It's not always movie based."
After the recent successful launch of the television series Hemlock Grove, starring Scotland's Dougray Scott (which perhaps explains Roth's uncannily accurate Scots accent), Roth's next film as a director is The Green Inferno, a horror about a group of hapless students from New York City who go to the Amazon to save a community, only to find it doesn't want to be saved. From the first pictures it is clear that there will be blood. Lots of it.
He famously doesn't like the real stuff, but fake blood is fine, even to do business in. During Aftershock, in which he also acted, he had to break off from filming, still covered in gore and dust, to sign papers.
"That's just the nature of making a movie," laughs the versatile Mr Roth.
The Last Exorcism Part II opens in cinemas on June 7.