Her phone rings a lot, because the bell on her Whitechapel studio - which she shares with her boyfriend, the artist Michael Landy - does not work. Without a mobile, I have to shout up from the metal doorway, which bears the legend: "Please, no fucking in the doorway", followed by the more pragmatic postscript: "Pick up your rubbers after use". The door is adjacent to one of London's most downmarket red-light districts.
Wearing looks out of the window and lets me in. She is dressed in the eccentric art clobber of woolly tights and colourful cardigan, and has black hair which is obviously newly dyed. In the last two years the 33-year-old has become increasingly prominent - which is pleasing, since she makes artworks (mostly on video) which are cerebral, minutely observed, compassionate and vaguely sinister all at once. She won the Turner Prize in 1997 and a glossy book of her work has just appeared on the Contemporary Artists list of up-market publisher Phaidon.
People singing along to their favourite tracks while listening to personal stereos, air guitarists playing pretend solos, intimate interviews with strangers on the street, people in masks confessing their innermost secrets, street alcoholics - these are all Wearing moments, captured on video and in photographs.
In person she seems unconfident, with a staccato, blurred delivery and a ready but anxious laugh. She explains that she likes making artworks that address communication because she has not always been verbally dextrous.
"I used to mumble and not talk very much. I slurred my words, and didn't realise when I left school that I couldn't make a sentence," she says. To this day she cannot manage the kind of public proclamations which so often seem required of the successful artist. But while the woman sitting on the sofa seems innocent and self- effacing, you detect a hint of evasiveness and a touch of steel. Yet you are still charmed and do not doubt her sincerity.
"I can't fake being naive," she says.
What is the thread that runs through Wearing's work? Is it, as some say, that her videos betray the tensions between public and private life? Or is she, as others declare, a documentary artist, a recorder of contemporary life? Some see her as a moral presence, giving voice to the marginalised.
"God, that sounds so pompous," she says. "But I am interested in what all kinds of people have to say."
The piece that won Gillian Wearing the Turner Prize, Sixty Minute Silence, was an hour-long video frieze of policemen and women staying as still as possible and saying nothing: at the end, although Wearing had not planned it, one of them shrieked with relief (she kept it in the piece). Wearing's other most prominent work, Signs that say what you want them to say and not Signs that say what someone else wants you to say, in which she invited passers-by to write on a card and be photographed holding it, has become a 600-picture library of startling dislocations. The most famous is a smug-looking businessman holding a sign reading: "I'm desperate". Recently Wearing was in the spotlight for the unfortunate reason that her work has twice been appropriated - to use the polite term - by the advertising industry. Last year, the Signs idea was used for a car commercial, featuring people holding cards in the same way, but flogging the disparity between person and placard for laughs.
"It was horrible and stereotypical," she says. "It brutalised the idea, particularly with their businessman holding a card saying: `At weekends my name is Mandy'."
She is not anti-advertising - indeed, Levi's used her Signs piece in the US and paid her for it - but she is still upset and confused: "I mean, how does it sell cars?"
But something upset her more, this time advertising a digital TV service by taking the device of dubbing children's voices on to footage of adults talking, as used in her piece 10-16. This cut deeper as it was created by agency M&C Saatchi and 10-16 had been bought by Charles Saatchi. Wearing felt "betrayed", would have liked Mr Saatchi to intervene, and has never subsequently spoken to him about it. She will never sell Mr Saatchi anything again, she says.
After the ad rip-offs, some sophisticates argued that Signs was itself inspired by the old Bob Dylan film for Subterranean Homesick Blues, in which he holds and discards the written lyrics. "Doesn't make any sense at all," she says. "That's just like the cue cards that television has used for years." Another journalist proposed that her Dancing in Peckham video, where she cavorted in a shopping centre, was a steal from the television series Candid Camera. "Total bullshit," she says. "I'd like her to find a copy of it for me."
Curiously, the issue that really exercises the public is whether the people she uses in her videos are real or actors. Some felt cheated to find that the supposed police in Sixty Minute Silence were indeed actors. "It didn't matter," declares Wearing. "Obviously to other people it did. The problem with getting real police was the time schedule."
She remains slightly evasive about where her subjects come from, believing it to be beside the point. Anyway, she says, everything about the Turner Prize is controversial.
While she enjoyed winning - she put the pounds 20,000 prize back into her work - Wearing was alarmed at the reaction that accompanied her new fame. "All of a sudden people got nasty," she recalls. "They avoid you."
Then the press started to call her, and at once her dread of talking emerged again. "You get asked your opinion on everything from `What do you think of Chris Ofili?' to knocking down houses. But my opinion is so crap."
Wearing comes from Birmingham, where her mother was a butcher and her father a television salesman. She attended comprehensive school where she was not particularly arty, though she recalls making masks and pottery. It was "a bad education", she has said, but she shows the quiet resolution of someone who has turned personal disadvantages into the strength that comes from self-knowledge.
She left school at 16 and, this being in the midst of the Thatcher years, started on a Youth Opportunity Programme, doing clerical work at an insurance brokers. There, two older women humiliated her by making her stand up and "speak properly". After three months' probation she got a job and stayed two years. Has this experience fed into her art? "To me it was just great that I got some money."
Her parents were apparently keen that she supported herself as soon as she could, and even now there isn't much interaction between them. Wearing likes this, she says, as it means they are uninvolved and put no pressure on her: she enjoys the consequent freedom and anonymity.
In her late teens Wearing and a friend came to London, and she began a few picaresque years working in offices, fast-food restaurants and pubs, and living in about 20 shared houses - inhabiting the world of the small ads, a sphere to which she was to return as an artist later in life. She blagged jobs, lost them, got new jobs.
"I realised that you could lie to get work and that you could make up your qualifications," she says. "It was slightly decadent, the Eighties." She recalls answering the phones at a film company, drinking all their Champagne, and going down to the then- cool King's Road tripping on acid, asking shops if they'd employ her. Although "intimidated by fashionable people", she forced herself to go through with the plan, just as she was later to force herself to go beyond embarrassment in her video artworks, such as dancing madly in a Peckham shopping mall and walking around south London with a bandaged face.
But Wearing became low when she found herself between jobs and with money problems, partly because she "didn't know how to get housing benefit" - that naivite again. And so she became interested in doing an art course. Her friend, a hairdresser, "used to draw and was into Salvador Dali": the favourite artist of the untaught and the double-bluffer. She got a job at an animation studio and admired the way they were "into their drawing". She entered Chelsea School of Art on a two-year BTEC course which she denigrates as: "the kind of course that 17-year-olds went on. Again I lied about the O levels. Luckily no one checked."
Wearing started painting, becoming interested in the school of London and painters like Frank Auerbach and David Bomberg. Just as the less-than- confident Wearing decided she would become a graphic designer, the teachers said: "We think you're a fine artist."
Without them we might not be here today, Wearing acknowledges. "I had bluffed my way through life and this was the first time that people said I was good at something."
At 22 she made her big move, to Goldsmith's, then at the height of its powers, where she began to realise her maverick talent. "I thought it was brilliant, the best thing I ever did. There were so many disciplines and people doing exciting things like performance art. One guy danced in his flat naked with pig trotters hanging around his waist! Possibly crap in hindsight, but great at the time."
At first, still into Bomberg, she painted flowers while tripping on magic mushrooms, then moved to different media, including photography and video.
By the time she did a fine art MA at Goldsmith's - which she left early - she had already started Signs, and she recalls encountering negativity from fellow students who had decided that it was unethical to collar strangers in the street, get them to write a personal message on a card for no money, then exhibit the results. "One told me that they were jealous of me because I knew nothing for ages and still had a lot to learn while they'd read too many books and knew too much," says Wearing, who seems inured to jibes.
By 1994 she had joined her gallery, the Interim in Hackney, and was well on the way towards carving out her singular niche in the art world.
Wearing has constantly challenged herself. Her first video piece, where she asked South-east Asian tourists what they liked about London, was a kind of exercise in getting over shyness, and she cringed when she played it back and heard herself laughing with embarrassment.
But, with characteristic self-discipline, she felt the fear and did it anyway: "A lot of my work is about inhibition and uninhibition - probably because I think I'm inhibited."
Two artworks particularly show this: Dancing in Peckham followed her fascination at watching a woman dancing crazily at the Royal Festival Hall. Then there was Homage to the woman with the bandaged face who I saw yesterday down Walworth Road.
"I wanted to put myself in the shoes of someone who sticks out for their eccentricity," she says, and admits that she had to have two whiskies before she went out. Back home, she found that her camcorder work was shaky. But she had made her piece the only way she could, as someone who admires "people who go through life without compromise, and stick to their character even when it means they remain unemployed or without friends".
She also challenged herself in Take Your Top Off, where she photographed herself naked in bed with three transsexuals, interested in how it felt to be between sexes: "If I'd done straightforward photographs it would have been boring and voyeuristic without telling you anything."
The transsexuals were recruited through small ads, a medium she has used to find participants since her first piece, in which she solicited bald men and then photographed the backs of their heads.
Why, I want to know, would people - particularly men - respond to a small ad placed by a woman artist unless they expected some financial or sexual pay-off? But Wearing is consistently amazed by the number of people who call up, apparently keen to take part in an artwork for little or no recompense. "You don't know who you're encouraging to come out of the woodwork," she muses.
One of her ads supplied both title and subjects for the work Confess all on video. Don't worry, you will be in disguise. Intrigued? Call Gillian. After placing it, she recalls, she suffered a couple of sleepless nights: "I thought someone [dangerous] might come in."
Characteristically, Wearing refused to give in to her fear, although the ad certainly drew a lot of responses. "No advert has worked as well as that," she says.
Many of the resulting confessions were about sex, which surprised her but which she recognises as being "at the root of so many problems". Has she since become a Freudian?
"I don't read too much into it," says Wearing. "A lot of my work is about not having preconceived ideas."
Nevertheless, the piece seems to get close to therapy, particularly a confession about incest. "He was trying to exorcise a problem, and saw it as being cathartic," she recalls. "He wanted me to tell him it was normal, and I couldn't." But despite her eye for behavioural nuances - one of the pieces in her Turner exhibition, Sacha and Mum, showed two actors enacting the alternating hug-and-fight paradigm of an abusive relationship - Wearing has never been on the analyst's couch herself.
Surely, given her interest and their vulnerability, her subjects must come to depend upon her? "You do get very involved afterwards," she says. "Sometimes it doesn't feel right, but it's just like going for a drink; you might meet again, you might not. I've never had anyone that wanted to stay in contact with me and I didn't."
The fact that Wearing's star has soared in the epoch of docu-soaps, video diaries and Oprah-style confession programmes appears to indicate a sort of pop synchronicity - after all, her work shows a journalistic intrigue with the extraordinary things that lurk under ordinary lives.
But while she admires intensely personal television documentaries with real emotional power - such as Michael Apted's 7-Up, which she has included in the book - mostly she hates this kind of programme.
"On the whole they are awful and nothing happens that gives you something you can go away with," she says. "Also, they quickly lose their freshness and naivite. As soon as people know what they're getting out of it, it ruins their purity." Wearing's method is by necessity amateurish, relying on an equality of frailty with her subjects.
"One of the reasons it works is because I find it difficult, and there's something about the way I stumble over the words," she says. "As soon as you start to dominate like a TV person they start saying more bland things."
Her work never seems exploitative: in her video (Slight reprise), which shows air guitarists miming along to their tracks, rather than mock them she seems to rescue the riffers from their own foolishness. "People say it's adolescent, masturbatory," says Wearing of this video. But she is more interested in the way that these would-be rock stars manage to lose themselves.
I notice that one is naked and seems to have an erection. "Half and half," corrects the unshockable Wearing.
Then I mishear her mumbled word "docu-soaps" as "donkey sex". She laughs and I realise that I've slipped into Wearing-space, where nothing is true and everything is permitted
`Gillian Wearing' is published by Phaidon at pounds 19.95