In the contemporary art menagerie, the paintings of Tomma Abts are odd creatures. It's not immediately obvious what to say about them. They don't have an explicit idea or trick. They don't make statements. There's no pay-off. They have character. There's a tone of voice you can't quite catch. You can watch them for a while. They're up to something elusive. That's what's odd and good about them.

Her pictures are abstract, and small, and they're all the same size, an upright oblong, 48cm by 38cm. Their colours are generally subdued, withdrawn. And they're each filled with a tense formation of shapes and lines. Angular or curvy, always sharp edged, these forms are painted flat, but often they make a little jump out into the third dimension, like a cardboard cut-out.

Things radiate, zigzag, intersect, daisy-chain, repeat. They fold, interlock, scatter, jam. But their patterns never properly click or dance. They suggest something being worked out or held together with great awkwardness and delicacy. There's anxiety and incongruousness. They look like holding positions, solutions to problems that cannot be solved.

Abts has said that they "show a state of mind". She gives each picture a human name as its title. You can certainly read them as mindsets, unstable or screwed up little personalities, relationships that have got stuck. But things aren't terminal. They always hold the possibility that the kaleidoscope might jolt, the tension break, precipitating a quite different state of affairs.

A worthy winner, then. And after this prize I think you'll be seeing a lot more of them. In a couple of years' time, every new book of philosophy and psychology is going to have a Tomma Abts on its cover.