A YBA who's still causing a big sensation

The Continental curators may not love us but here in Britain our galleries have been producing a rare succession of major shows of our contemporary artists.

Last year it was Tracey Emin. This year we have Hockney, Lucian Freud and Damien Hirst all pulling in the crowds. And now we've got Gillian Wearing at the Whitechapel with her first retrospective.

Last but not least, one should say. For of all the artists working today she is the most personal and the most penetrating. You may or may not count video art as among the proper forms of art, but to see Wearing's short films or photographs is to experience a mind that is at once compassionate, complex and critical. It's easy enough to put her work into the category of the feminine confessional or to look at it as a kind of psychotherapy for the damaged and the marginalised. But that doesn't do justice to the subtlety with which she takes on the individual experience through the masks we wear and the performances we put on.

The exhibition begins, as it ends, with self-portrait, in the form of two powerful life-sized photographs of herself, staring out at you, big eyes and unblinking. Go closer and you see that the eyes are real but face is in fact a mask. The effect is stark and startling. Are you seeing the real person or is she hidden behind that smooth unageing face? Are the eyes blank or seeing as they challenge you.

This playing around with presentation of the self is what makes her such an interesting, and searching, artist. Now 48, a Young British Artist (YBA) and a Turner Prize winner in 1997, she was a year behind Damien Hirst at Goldsmiths College and a contemporary of Tracey Emin. She's like neither. Her work doesn't hit you full on like Hirst's nor is it openly self-confessional like Tracey Emin's. Instead, it draws you in to the story of people's inner lives, both what they say and what they would like to say but haven't.

It started with a series, Signs That Say What Want Them to Say and Not Signs That Say What Someone Else Wants You to Say (1992-3), in which she asked people in the street to write down on a large piece of paper a statement that they wanted to make and then photographed them holding the result. At it simplest – the policeman who writes "HELP" in capital letters and the city-suited young man who declares "I'M DESPERATE". But most are not really cries from the heart as such. They're the assertions of what people want to say when they know they're being photographed – sometimes witty, sometimes aphoristic and often quite wry. One lady just declares "Enough Said", while a young girl looks down on the paper on which she has scrawled tight in a corner the ambiguous thought "convenience causes apathy".

It's a delicate hinterland of self-pretence and self-knowledge that Gillian Wearing navigates with great care and persistence. The mask is one means to this end, not least in her autobiographical works. Prepared with meticulous attention to detail, she dons face and full body masks to adopt the persona of family and heroes, putting on the clothes and faces of grandmother, mother, father, brother, sister and uncle, and her artistic influences, Warhol, Mapplethorpe and Arbus. It's not a revelation through unpeeling but an understanding of the influences that make us what we are.

Wearing's other technique is the voiceover and the masked confessional. Starting with Confess All on Video. Don't Worry, You Will Be in Disguise. Intrigued? Call Gillian (1994) she has added layers since. In one case, 2 into 1 (1997), she records twin children and a mother talking about each other and then switches voices so the mother speaks the words of the child or vice versa with disconcerting effect. In Trauma (2000), she asks people to tell their most personal secrets from behind a mask of the age when it happened (more often than not, child abuse).

She does the same with video. It began with filming herself doing a dance, without sound, in the middle of a shopping centre in Peckham in 1996. By now that looks tame as the social network sites have made such demonstrations commonplace.

In the years since then, though, she has taken it much further. In her latest video, Bully (2010), on show for the first time in the UK, she use a method acting coach to organize a group of adult non-actors into performing a scene, based on the real experience of one of them, of childhood bullying in an estate. You see the group being given their instruction in the studio, you see them gradually taking on their roles of victim or victimisers with increasing fervour, you see the central figure breaking down in tears as he remembers it all.

It's not quite clear where Gillian Wearing goes next with this. You can envisage the Bully formula being developed with greater complexity and more layers. She recently made a full film, Self Made of professional coaches orchestrating a series of individuals to make confessional films about themselves. She's also recently been working with artificial flowers to imitate the real ones in still-life paintings and has, at various times, sculpted small-scale memorial statues to ordinary people, giving them all the dignity of the more famous. You understand the point but it can't be said that they have anything like the effect, or the creative force of her film and photographs.

In that area she is peerless, and deeply affecting. In one of the short videos shown, Prelude (2000), she films a particularly mouthy and extrovert addict. She'd intended it as a group portrait but, taken by the personality of this woman, tried to get in touch to do a film of her only to discover that the girl had died in the meantime. So instead she has voiced over the clips of the girl silently talking to camera with the words of her twin sister telling of her grief at her sibling's death and saying how far her mother had disowned the dead daughter, even at the funeral. I am not ashamed to say that I silently wept as it unfurled.

Accident or design, art or performance? It doesn't really matter. It has its own painful truth.

Gillian Wearing, Whitechapel Gallery, London E1 (020 7522 7888) to 17 June