Doubletake'', at the Hayward, is a large exhibition of contemporary art devoted to the theme of, um, er, what was it again? Oh yes: ''Collective memory''. The show got off to an inauspicious start when one of its extramural projects, a poster for the London Underground designed by Jeff Koons, was turned down by LRT, apparently on the grounds that Koons' prominently printed name might be misinterpreted as a racial slur on London's black population. Needless to say, the content of the poster, a photograph of Koons and his wife, La Cicciolina, their naked bodies diplomatically obscured by three kitsch statuettes of Scotty dogs, had nothing to do with the decision to censor. Still, it may not be such a great loss. The extent to which a picture of Mr and Mrs Koons adopting the doggie position would have furthered insight into the relationship between contemporary art and collective memory is questionable.

''The artists in this exhibition,'' according to curators Lynne Cooke, Bice Curriger and Greg Hilty, ''share an equal distrust of the securely social and the purely personal.'' Some of them may also, with hindsight, have developed a certain distrust of the ingeniously curatorial. Quite what all these artists are doing together in one exhibition is less than clear. There is precious little evidence of anything much like a collective spirit, and the heterogeneity of the art in ''Doubletake'' is heightened by Italian architect Aldo Rossi's redesign of the Hayward for the occasion. Rossi has carved up the exhibition galleries into a series of cubicles, which most of the artists present have furnished with evidence of an assiduously cultivated singularity. The result is, effectively, to sabotage the curatorial generalisations said to provide the exhibition with its logic.

So while you process from, say, French artist Sophie Calle's surveillance-style photographs...