Slow looking is an increasingly prevalent strategy for enhancing visitor engagement in the gallery, yet there is little research to show why looking at artworks for longer should be beneficial. The curator of a recent exhibition of Pierre Bonnard at the Tate Gallery in London encouraged viewers to look slowly in order to enrich their experience of his paintings. This article explores some of the reasons why Bonnard's work in particular rewards the viewer who spends more time studying it. Our account draws on various scientific studies of the ways in which observers process colour contrasts, spatial configuration, and figure-ground segregation in artworks and in everyday vision. We propose that prolonged interactions with works of art can facilitate perceptual learning, and suggest ways in which these effects could be empirically studied using psychological methods.