If the museum show is increasingly becoming crowd-pulling spectacular (and it is, witness the long and patient queues outside the new Whitney in New York) then Carsten Höller is an above-the-title, headline act. In the art-show-as-circus model, he is the ring master and unapologetically so.

Decision, Höller’s new show at the Hayward Gallery in London, and the largest survey of his work in the UK to date, is he acknowledges, a funfair with a conceptual twist. As the title suggests, visitors are immediately faced with a choice of entrances before being funnelled into dark steel tunnels - Decision Corridors - with no real indication of where the tunnel is taking them. Leaving the show offers a similar dilemma. You can exit through the gift shop, as is now the traditional departure point, but Höller would much prefer you took one of the two (now trademark) isometric slides mounted on the side of the building, leaving the show, as he says, with the 'sensation somewhere between delight and madness.'

And the exhibition, designed in collaboration Delvendahl Martin Architects offers other Wonderland-worthy choices along the way. Whether to take the pills that drop from the ceiling, contents and effects unknown for example. Visitors also have to navigate around flying mushrooms or turn the world topsy-turvy with the Upside Down Goggles.

For £300, truly committed Höllerites can even book a night at the museum in one of the two Roaming Beds, twin robotic berths which creep around the gallery using a complex system of lasers and radio beacons to avoid incident and injury. Dream-enhancing toothpaste and morning tea or coffee come as part of the deal.

For the Hayward, it is a dramatic closing act. Once Höller has demounted his slides, the gallery will shut for two years of refurbishment work. Höller spoke to us during the installation of Decision...

Wallpaper*: Do you think about a cumulative effect that builds with each interaction in the exhibition or can they happen randomly?
Casten Höller: I’m not really planning effects, I’m offering possibilities. This show is not just about you experiencing these art works, if you want to call them that, it is about whether you want to watch other people experiencing them. It’s not that I’m turning up and loading this space that with my inner visions or whatever, translating them into an object. I want to work with the people who come here.

W*: It’s important that it is a shared experience whereas most people turn up to a gallery and wish everyone else would go away?
CH: It’s not just shared, you are becoming part of the exhibition, you are becoming something to look at. It is also about indecision as well as decision. You pick two corridors, each 75 m long and go up and down. And at certain points you will be above the other people, walking on top of them, or underneath them and you will hear them. I like the idea that when you go into the show you have to go through something, like a lock in a canal.

W*: And then when they get into the open gallery space, is it still a kind of ‘directed’ experience?
CH: Well, the two corridors meet and there is a kind of corridor and then you will see the flying mushrooms, a kind of mobile, which you can push and the whole thing will spin.

W*: We have to talk about the slides of course. Is there much science in terms of engineering the slide to create a particular experience?
CH: Well, there is science in how steep it slopes and how it curves, otherwise you pick up too much speed. But you need to go quite fast so you can’t stop. Otherwise that would be dangerous.

W*: You think of them as practical architecture?
CH: Absolutely. I’ve made propositions to architects to use slides as a way of getting around a building or going from one building to another.

W*: But it is important the slides look beautiful, they don’t just shoot people out of the building?
CH: Absolutely. And they do.

W*: And is the Hayward a difficult space to work with?
CH: No, I like it. It’s not the most beautiful example of Brutalism but I like it a lot. It’s very yellow.

W*: Your exhibitions are an on-going battle with the idea that art is something that you stand a metre-and-half away from and stare at for 20 seconds, hoping for something to happen, that you find the sublime.
CH: Well, there is nothing wrong with that. It happens sometimes. There is a reason why people do that.
Some art though doesn’t work with other people. One of the first art shows I went to was at the Rothko Chapel in Houston and I was all alone, there was not even a guard there I think. I was a scientist, still working at Texas University and I went in sceptical but I came out with something new and profound, not really describable in words but comparable to a religious experience.  Then I saw the Rothko again at the Tate but there were so many people and the idea that you could contemplate them in such a context is ridiculous. That is why this show is as much about the other people. But you can also stay the night here and see the work alone.

W*: You have talked about the area between delight and madness. There is a human need for that. It is there in drugs and alcohol, in extreme sports, in all kinds of things?
CH: It is definitely part of our intelligence I would say, that we are curious about these other states of being, these other ways of looking at the world. It is a driving force. This utilitarian way of looking at things is one way, but there are other ways.

W*: There are these big gallery spaces now where you can become a kind of controlled extreme space...
CH: Well, this exhibition is a kind of a funfair, but that’s what exhibitions are these days. They are just pretending not to be, which is very strange. It’s not just that I want to rehabilitate the funfair, its just that I think that there is an idea in the funfair that is really worth exploring. Especially in an era when art has become such a mass phenomenon. That’s what people do, they come to the art museum rather than the funfair. I want to create a new kind of fun, an art kind of fun.