From the mid 1980s Riley's work began to change direction: having introduced her Egyptian colour scheme within a vertical format, she then disrupted this with the use of diagonal divisions between the colour areas. In January 20, Study, these diagonals appear to cross over the vertical passages.
Paul Moorhouse comments, 'Most significant of all, the lattice effect, which results from the way the diagonals appear to pass through or in front of the verticals, opens up the space of the painting in new and unexpected ways. Previously, the space in Riley's paintings had appeared to advance towards the spectator. Now the reverse is made to happen. A strange, ambiguous space is sensed in the opposite direction - opening up depth and drawing the gaze inside the virtual space of the painting. However, this is an unstable, elusive arena in which planes of colour alternately advance and recede, suggesting positive shapes and then apertures, depending on the eye's inclination and its response to a particular context' (see exhibition catalogue, Bridget Riley, London, Tate Britain, 2003, p. 24).