Perception of Chromatic Motion Requires Luminance Interaction

There is an ongoing debate related to whether chromatic motion perception arises as a consequence of a chromatic signal only (eg Wandell et al 1999 Neuron 24 901–909) or a signal that is essentially based on luminance processes (luminance artifacts) (Mullen et al 2003 Vision Research 43 1235–1247). These two views conform to the idea that colour and luminance processes are physiologically independent (Livingstone and Hubel 1988 Science 240 740–749), but according to other reports many primary cortical ‘V1’ cells respond to both colour and luminance contrast (eg Vidyasagar et al 2002 European Journal of Neuroscience 16 945–956). A psychophysical task was designed to test whether possible interaction between luminance and chromatic contrast could account for perception of chromatic motion. It is shown that subjects respond in a manner that reflects involvement of both processes.