Andreas Whittam Smith: Has the Turner Prize lost its way?

I don't get it. This is, like Duchamp's urinal, art only because the artist says it is art

The annual exhibition of the shortlisted entries for the Turner Prize, which is to honour the achievements of an outstanding artist under the age of 50, living and working in Britain, regularly raises the issue: is this art?

The new show is no exception. Greeting visitors to Tate Britain, in London, are a video installation which contains within it a working production office (Phil Collins); a quasi-scientific installation (Mark Titchner); new sculptural works described as "deliberately anti-heroic" (Rebecca Warren) and a set of 11 abstract paintings (Tomma Abts).

"Is this art?" is a famous trick question. Robert Hughes, the critic, gave the wrong answer when he first came across contemporary art as a young man in Australia.

In his autobiography published this month, he recounts that a Sydney museum had put on an exhibition of abstract painting in Europe. "Everyone, including myself, thought it was some kind of joke," Mr Hughes recalls. One painting in particular struck him as peculiarly offensive, with its paint "daubed on" and its main motif "the numeral 47 painted in black in a funny-looking cursive script". It was by Miro.

One is also put on notice to retain an open mind by the distinguished list of previous Turner prize winners in its 22-year history. They include Howard Hodgkin, Gilbert and George, Anish Kapoor, Rachel Whiteread, Antony Gormley, Damien Hurst, Gillian Wearing and Chris Ofili.

The results are good because the method of arriving at a shortlist and then a winner are well conceived. A jury spends a year making its choices. It is always chaired by Sir Nicholas Serota, the director of the Tate, and this year it also comprised a writer, a gallery director, a curator from New York and an academic, Their choices are then exhibited for two months and are accompanied by filmed interviews with the artists. Finally, the announcement of the prize winner is broadcast live by Channel 4 (4 December).

All the same, I struggled this year to know what to think - not realising, as I shall recount, that help was at hand. In Phil Collins' installation we watch continuous film of people being interviewed on Turkish television, whose lives have been ruined, as they believe, by appearing on reality TV shows.

We can also see a fully functioning office called Shady Lane Productions that is planning the artist's next set of projects. I don't get it. This is, like Duchamp's urinal, art only because the artist says it is art.

Some measure of Mark Titchner's work is given by its ridiculous title: How to change behaviour (Tiny Masters of the World Come Out). You see hand-chiselled "machines", a computer-designed billboard and kinetic sculpture that employs optical illusions and hypnotic effects to manipulate the viewer's perception. I didn't feel negative about this; rather not much moved. The work is oddly artless in the sense of lacking guile, being unsophisticated and unworldly, even unaffected. Yet the objects have charm.

As to the other two shortlisted artists, there is no question that Rebecca Warren's unfired clay sculpture, bronze figures and vitrines filled with various found objects and Tomma Abts' abstract paintings in acrylic and oil are "art" as conventionally defined. I preferred Abts, and I would vote for her. Nonetheless, I left the show after the second of my two visits thinking that this is not a vintage year for the Turner prize.

And then, next day, I became certain. For I went to the Royal Academy to see USA Today, an exhibition of paintings, sculptures, photographs and installations by 40 young American artists. With its sheer energy (Kristin Baker), its elegance (Ryan McGinness and Matthew Brannon) its wit (Aleksandra Mir) and its cleverness (Wangechi Mutu), it is a thrilling spectacle. I think only Abts' work would have got into the USA Today show.

It would be wrong, however, to take the exhibition as fully representative of the state of American contemporary art. More accurately, it is what currently interests Britain's greatest collector, Charles Saatchi. All the work on show comes from the Saatchi Gallery. Is it Mr Saatchi, or American artists in general, who tend to see the world not as utopia but dystopia, where deprivation, oppression and terror are our everyday condition?

Some artists in the show focus on the bleakness of urban life, where decisions that affect our lives are made by people we cannot reach, where social divisions are like chasms, and where people often feel as if they were worker ants in a huge nest. And some are anti-consumerist, like Banks Violette, who has an installation which comprises old refrigerators and other domestic equipment, as if found abandoned in a store room after a new ice age, their owners long since disappeared, presumed dead, and everything now covered with a salty white frost, all utterly useless.

Yet even I, one of nature's optimists, more likely to imagine utopia than dystopia, thoroughly enjoyed USA Today. It isn't like an art museum, or even a normal Royal Academy exhibition, where only good stuff is on display. There is dross, too. But above all, USA Today insistently asks questions. Erick Svenson's model of a dead white deer on frozen city cobbles, what was that all about? The distorted female figures in Inka Essenhigh's oil-on-linen picture Shopping, what were they telling us?

Is this art? Yes, it makes us see more clearly, feel more passionately and think more deeply. But, of course, art provides no answers.