Stuff and nonsense

"A unicorn is a perfectly good horse but with a horn on its head," he says. "That is dangerous. It's a real health and safety issue. You don't need me to tell you that."

Having indulged me on this theme for a moment or so, Shrigley bites back a smile. "The truth is I don't love or hate any of these things," he says. "It never occurred to me to have an opinion about any of them. Why would one like corridors and hate celestial beings - or vice versa? That is the proposition I'm making."

Shrigley does a canny line in darkness, dry wit, pathos, self-deprecation and existentialism, describing the 300-odd drawings contained in Weak Messages Create Bad Situations: A Manifesto as "a satire of an instructional or reference book". It is a "general setting the world to rights", but as he concedes, none of the missives or declarations are things he particularly ascribes to. Rather his penchant is for "making statements and then figuring out what they mean afterwards", likening it to playing "a character", albeit one with a "self-contradictory and scatological" world view.

"The only way I could do this book was by pretending to be the character that wrote it, the very dogmatic person who made all of these statements," he explains. "I'm pretending to be them, it's not actually me."

When we meet on a weekday morning amid the colourful chaos of his Glasgow studio, Shrigley, 46, is not in character. Well, not the one I was expecting anyway. "I have a different character when I'm talking to journalists, that's for sure," he says. "That's me being honest. Whereas when I'm making art I'm just mucking around and basically talking a lot of nonsense.

"Some people are a bit shocked that I can articulate myself about the work and don't talk a lot of nonsense in interviews. I think it would be disrespectful to talk a lot of nonsense."

In person, Shrigley is far more subdued than the kooky, madcap tone his distinctive, black-inked drawings may suggest. He has a shy, introverted manner that could be mistaken for aloofness were it not for his deadpan delivery and knack of turning every second sentence into an illustration of not taking himself too seriously.

His studio, housed in the former bonded warehouse of a whisky distillery, is an airy space, filled with plaster cast moulds, stacked canvases and overflowing cardboard boxes. A series of eye-catching, outsized black hand-prints adorns one wall, beneath which is a tiny single mattress covered in a lumpy-looking patchwork wool blanket, which Shrigley reveals he often curls his 6ft 5in frame up on for an afternoon nap.

The room is limited in seating options. Shrigley mutters something about disliking Ikea, before insisting I take the "big chair", a bar stool-like contraption that makes me feel like a contestant on Blind Date. Through the window can be seen the Forth and Clyde Canal, a bevy of swans gliding atop the murky greenish-grey water.

The past two years have arguably ranked among the most pivotal of his career to date, seeing Shrigley nominated for the 2013 Turner Prize and then announced in February as the latest artist whose creation will grace Trafalgar Square's fourth plinth.

When he was first shortlisted for the Turner Prize, Shrigley joked that his nomination at the ripe old age of 45 - a mere five years under the upper limit for entering - was the judges "scraping the barrel". It was an experience he would appear to have loved and loathed in equal measure.

"I guess because I'm probably a bit older than the average age of the current Turner Prize nominee, I went into it very much with my eyes open," he says. "I felt I couldn't really moan about it because I knew exactly what I was doing and I didn't have to do it. I tried to just embrace the opportunity and learn from it. I was really quite happy. It was stressful and takes up far too much head space, but I think you learn a lot about the art world and your place within it - which isn't necessarily something pleasant."

After years of taking an "inverse pride" in not being nominated, Shrigley admits to being perplexed to discover how much gravitas is truly given to the Turner Prize, not merely among his peers but the wider public too. "Finding out that it does actually matter commercially is quite disappointing," he says. "Just being nominated made a difference. You sell more artwork. You notice that and it's really disappointing - in a funny way."

His Life Model installation for the 2013 Turner Prize exhibition in Derry-Londonderry comprised a three-metre animatronic naked figure urinating into a bucket, Shrigley inviting members of the public sit at one of the many easels surrounding the sculpture and capture its misproportioned, cartoonish physique.

Not everyone got it; the piece sparked some outrage which saw school visitors offered an alternative entrance so they could avoid it. "Oddly, the same thing happened in Glasgow," he muses. "I was thinking: 'Oh, it won't happen in Glasgow', but it did. I showed it at The Young Gallery, which is for children in the east end of Glasgow and a charity I'm patron of.

"I jokingly said: 'At least we aren't going to have school groups not being allowed to draw it.' They [the gallery organisers] were like: 'Ha, yeah, that will never happen' but sure enough it did. [There] were mums saying: 'It's a big naked man.'"

His incredulous tone suggests Shrigley isn't quite able to get his head around the logic of such detractors, but he plumps for diplomatic tact. "Well, I'm not a parent so it's not my place to say," he ventures. "I think it's an odd thing. None of my friends' kids would be offended by it in the slightest but" - he catches himself - "it's not my place to say."

Born in Macclesfield and brought up in Oadby on the outskirts of Leicester, Shrigley moved to Scotland to study at Glasgow School of Art in 1988 and never left. By his own admission, he views being commissioned for the fourth plinth as a far greater achievement than his Turner Prize nomination. "For me, it is more exciting as an artwork," he says. "The Turner Prize happens every year and everyone jumps through all those hoops. But with this you get to make something which will be exciting and interesting. Because the context changes all the time - political and social - the way in which people perceive it will be different. It's quite a challenge in a way. I suppose what interests me is that it's very oblique and unusual because of the distorted nature of the object."

His 10m-high bronze sculpture - a comical thumbs-up described by Shrigley as "a deeply naff gesture" and "both sarcastic and sincere at the same time" - will take up position in 2016. Before then a piece by the German artist Hans Haacke of a skeletal, riderless horse with an electronic stock market ticker tape tied to its leg will replace Katharina Fritsch's giant blue cockerel, which has ruled the roost for the past 18 months. London's mayor, Boris Johnson, said the commissioning group had "chosen two very different sculptures" with each being "wryly enigmatic in their own way".

The stark contrast between the two artists' approaches appears to both intrigue and bemuse Shrigley. He relays with awestruck wonder the painstaking attention to detail contained within his fellow artist's vision. "He wrote a press release saying: 'Stubbs' famous horse was first exhibited in the former National Gallery and he painted it in the same year as Adam Smith's very famous treaty on the nature of commerce etc etc,'" says Shrigley. "Every little detail was tied up like a ribbon on the horse's leg. I was really impressed but, in a way, it made my attitude towards it all seem incredibly flippant to the point of being disrespectful.

"I'm not that kind of artist. I admire people who are, like Hans Haacke, and think he's a great artist, but I don't want to be so in control of the context because I don't believe it is actually possible to be in control. For people who wish to have a crossword type answer to contemporary art then I'm sure Hans Haacke's work will be a lot more successful than mine.

"It's like printmaking. The nice thing about making prints is that you never quite know what you are going to get. The artwork happens as a result of the process, rather than the process simply being a means to an end."

Shrigley has various other bits and pieces in the pipeline, among them a collaborative album, Music And Words, with songwriter and Arab Strap co-founder Malcolm Middleton, which will be released next month.

Billed ominously as "a tale you shouldn't tell your children before bedtime", it marks his latest foray into spoken word album territory following on from Shrigley Forced To Speak With Others, released in 2006, and Worried Noodles a year later.

It is a project more than seven years in the making, an idea first forged when Shrigley created artwork for Middleton's A Brighter Beat album in 2007. Among those lending their vocals to the album are Still Game star Gavin Mitchell, former High Road actor Bridget McCann, Californian performance artist/comedian Scott Vermeire and Shrigley himself. There will be a limited vinyl run of 1,000 12-inch records, each with individual artwork.

In the album blurb, Middleton, admits to misinterpreting the song Sunday Morning as a "scathing attack on the pomp and arrogance of religion", only to discover it was "just about willies and was recorded on a Sunday morning".

Shrigley takes up the tale. "I had given Malcolm all of these unedited recording sessions that I'd done over a period of two or three years," he says. "The engineer had called the file 'Sunday morning' as that's when it was recorded. Malcolm kept asking me: 'What's this about? What's that about? Have I misunderstood that?' As a visual artist that is just a really bizarre question to be asked."

And it's about willies? "The central line is 'bong your dong against the gong' - so it's also about musicianship," he insists, laughing.

The preview taster sample is a track called Story Time, a graphic tale about the reality of animal life. It includes the catchily jovial mantra "we hate life". And copious swearing. Shrigley's brow furrows when it's mentioned. "It's not really very representative of the album," he grumbles. "It's disturbing. Harsh and horrible. I thought, 'Oh, I don't like that at all', but for some reason everyone else seems to like it."

So no PR spin here, then. It is this unshrinking brand of honesty, among other things, that Shrigley reckons would make him a rubbish politician. "I'm not actually certain enough about my own views," he says. "I think morally one is obliged to respect other people's arguments and to understand the validity of those arguments. I'm far too honest to be a politician, lawyer or any of those things. That is not necessarily a virtue - it's probably a shortcoming."

Weak Messages Create Bad Situations: A Manifesto by David Shrigley is published by Canongate Books on Thursday, priced £25. The album Music And Words is released through Melodic on December 15