Colloquium: Motion illusions, eye movements and Bayes

Most of the work on motion perception ignores the fact that the eyes move to track targets of interest. Movement in the image therefore combines object motion and self-motion. To disentangle the various sources of movement, the visual system uses ‘extra-retinal’ information from the motor system to compensate for the effects of self-motion. Evidently the compensation is not always complete: I shall show examples of some well-documented motion illusions that occur when we make pursuit eye movements. Vision science typically places the blame for these motion illusions on inaccurate sensory processes. Here I present an alternative view, based on the idea that sensory processes are not inaccurate but imprecise. In the course of doing so, I reveal some important limitations of current Bayesian models of motion perception.