Yoko Ono: To The Light, Serpentine Gallery, London

Childish and brainless, Ono lives down to her name

There is something almost exquisitely fatuous about the work of Yoko Ono. To such an extent, in fact, that as we walk around what amounts to an anthology of almost 50 years of so called art-making, we find ourselves falling into a kind of coma of disbelief that ideas so paper-thin, so emotionally weightless, could have continued to interest those whose job it is to put art of merit in front of the public. There's so much brainless gesturing here, so much dated radicalism, so much art about as valuable as a random puff of fetid air from last night's lover. Having said that, it is perhaps good to be reminded that we all still care passionately about John Lennon and his buttocks.

Consider an idea particular to this show, for example, Smilesfilm. Everyone is invited to participate. You go to a photo booth, smile at the camera, and all the smiles will eventually get uploaded to a film of smiling faces that will lift all our spirits, induce universal camaraderie, and perhaps even expunge hatred from the world. Are you kidding? Can anything have been imagined quite so irritating and simple-minded as this?

So much of the show is in this vein – tiny, faux-naif, childlike (childish, more like) ideas that supposedly exist to bond us in some ill-defined way or to open our eyes to the marvels of every insect on which we have not yet stepped. There are lots of very poor poems on the walls about how spaces are infinitely expandable in the mind. The show seems to include an element of the participatory, but perceptions can sometimes deceive. I come across a white stepladder mounted on a white plinth. On the ceiling above it there's a painting which seems to invite scrutiny. Does it have markings on it? Perhaps. A magnifying glass hangs in the air from a piece of string, within easy reach of the top of the ladder. May I go up, I ask an attendant? No. The last time this happened I was at the Mori Museum in Tokyo. I spotted a heap of smashed crockery and a hammer. This was by Yoko too. May I smash it a bit more? I asked. No.

Outside the gallery we come across the Wish Tree. Everyone is invited to write a wish on a label, and tie it to a branch. I read one or two. This is the one Yoko will swoon over if she ever gets to read it: "Wishes: world peace, equality, happiness." This is the one I liked best: "I wish I knew what to wish for."

Until 9 Sep (020-7402 6075)