The Role of Pattern and Flicker Mechanisms in Determining the Spatiotemporal Limits of Velocity Perception. 2. The Lower Movement Threshold

For slowly-drifting foveally-presented gratings of 1 cycle deg⁻¹ and above, continuous movement can be perceived at stimulus velocities greater than about 1 min visual angle s⁻¹, irrespective of spatial frequency, providing stimulus contrast is greater than 0.01. For coarser gratings, the minimum perceivable rate of drift is determined by the detectability of the stimulus and is strongly dependent upon both spatial frequency and contrast.