My old art-teacher always seemed relatively traditionalist to me, as you might expect of a middle-aged, well-fed, head-of-department at a Church of England school. An oil-painter and ceramicist, and the teller of entirely pointless anecdotes, he had an extremely violent antipathy to any kind of comforting bullshit/avoidance, once asking a student midway through a life-size painting of a naked man, “What are you doing? Where’s his cock? If you don’t give him a cock, I will, when you’ve gone home.” It was a fair point, anatomically speaking, and my art-teacher pronounced the resulting Indian-ink depiction to be “Much better. No one’s going to argue with that.’“ I’d like to say that that was the point when I realised that I genuinely respected him – which I do, now – but back then I just found it consistently funny that his surname was Cockburn.

Little has altered in the world of Gilbert and George. They still look and dress like the modern-art Morecambe and Wise

In fact, I still find it funny, and when I found out that Mr Cockburn attended Central Saint Martins along with Gilbert & George, I imagined that they would have found it pretty funny too. Because there is something as inescapably juvenile about the works of G&G, the inseparable gestalt entity of nineteen-seventies and eighties British art, as there is about schoolkids muttering ‘Cock-burn’, and almost suffocating themselves with laughter. From the very start of their career, Gilbert Proesch and George Passmore, having declared each other to be “living sculptures” in 1969, have traded almost exclusively in stating the apparently obvious or juvenile from behind the straight-faced irony of the Gilbert & George image. Early work would see them videoing themselves packing away gin and tonics to the banging tunes of Elgar and Grieg, remarking repeatedly that “Gordon’s makes us very drunk”, (Gordon's Makes Us Drunk, 1972), while later pieces would see self-portraits as nine-feet tall Fates giving their hapless victims two-fingered salutes from either side of a seven metre long canvas (The Fates 2005), or find them asking the perennial question Was Jesus Heterosexual? (2005).

Indeed, in the light of their first major retrospective since 1981, which opened at Tate Modern on February 15 this year, the briefest of glances shows that little has altered in the world of Gilbert & George. Still they look and dress like the modern-art Morecombe and Wise, still their favoured mode is the massive and many-panelled photo-collage, still they tend toward the more grotesque manipulations of symmetrical arrangement, still they have a healthy love of the puerile joke. I still find myself smirking, for instance, when I hear the now sixty-year-old George quoted as saying that hoodies are “The only garment, we feel, which combines the qualities of the foreskin and the condom in one piece.”

Of course, testing the one-dimensionality of the audience’s response is a trick on can only play for so long - but that is not to say that the expansions of the juvenile or obscene can’t teach us something about art

Yet their fundamentally juvenile fascination with swearwords has led them to explore the under-belly of British society. The Dirty Words Pictures, the duo’s most enduring and divisive work, finds them extrapolating graffiti insults, curses and obscenities into a whole exhibition’s exploration of the prejudices and tensions exhibited on the walls of 1970’s Spitalfields. They may simply be enjoying the chance to plaster ‘Cunt Scum’ across a gallery wall, but in their ever-perfect matching suits, G&G simultaneously make a case for the power of the deadpan in the face of the crushing ridiculousness of reality. Their work is less about shock – who really finds ‘piss’, ‘shit’, ‘fuck’ or ‘cunt’ shocking anymore? – than it is about testing the one-dimensionality of our responses to what we see, whether it be spray-painted on the street, or arranged in a gallery.

Of course, testing the one-dimensionality of the audience’s response is a trick one can only play for so long – especially when the methods of playing it show no signs of changing either. Gilbert & George may be changing their references, but their suits, pictures and sense of the shocking issue seem to be stuck two decades behind us.

That, however is not to say that the expansions of the juvenile or obscene can’t still teach us something about art. If dirty words are a favourite of schoolchildren everywhere, so is the doodle, the biro transformation of a textbook into a feast of sexual positions or gruesome caricatures. The men behind this year’s other high-profile retrospective, Jake and Dinos Chapman – prominent YBAs and former assistants to Gilbert & George – incurred the wrath of critics such as Richard Hughes whilst simultaneously gaining a Turner Prize nomination, for doing exactly that. Their textbook, however, happened to be a set of Goya’s iconic etchings The Disasters of War – not photocopies from a catalogue either, but one of the few sets printed from the original plates in the 1930s to commemorate the Spanish Civil War.

Painstakingly “rectifying”, as they put it, the faces of Goya’s victims and torturers into those of cartoon puppies and clowns, the Chapman brothers produced Insult to Injury, Goya’s eighty prints remodelled for the 21st Century. Having approached the piece a little sceptically, it became clear to me that something important has happened to the notion of ‘shock-art’ that Gilbert & George seemed to conform to. Whatever the Chapman brothers’ back-catalogue may say about their fascination with the conventionally shocking – from their Fuckface and Two Faced Cunt mannequins, to their miniature Nazi Hell – the Goya etchings may be the first time they really shocked the viewing public. The outraged accusations of defacement immediately levelled at them showed that if you really want to cause a tantrum in the art-world, you have to hit it where it hurts: in the canon.

If contemporary artists are to be accused of recycling the ideas of nearly a century’s worth of ‘modern art’, the Chapman brothers have taken it all with a literalism worthy of the most obtuse schoolboy in history. But they are more than petulant toddlers scribbling on the cultural landscape and its finest products, they have found one of the few ways left to worry the modern establishment, in all its apparently free-thinking glory. And in doing that, I think they might just have proved that the puerile still has something to say.