Wake us when it's over

Even by the normal standards of high conceptualism, Dan Graham's early works are as desiccated as dust.

Consisting of proposals placed as ads in magazines, performances described in minute detail as interminable text pieces and lists of objects that suggest scientific categorisation, these works from the late 1960s and early 1970s often masquerade as socio-scientific investigations, each matched by suitably arid language.

One magazine ad requests someone with medical knowledge to describe, in purely scientific terms, what happens to a penis as it loses its erection, while two people, in a taped performance, use words, gestures and actions to indicate in what ways they're alike. The tape is neither clear nor compelling.

The degraded quality of the videos reinforces this sense of depressing desiccation: when addressing audiences, Graham appears like a nuked hologram. Graham was always a fairly minor conceptualist, so heaven knows why these works have been resurrected.

Until Aug 28, Lisson Gallery, 29 Bell Street NW1, Mon to Fri 10am to 6pm, Sat 11am to 5pm, free. Tel: 020 7724 2739. Tube: Edgware Road