Figure 2.

Schematic illustration of method used by Lu et al. (2) to demonstrate contribution of chromatic contrast to third-order motion detection. A movie consisted of four sequentially presented frames. Odd frames contained a red/green striped pattern; even frames contained a striped pattern formed of coarse and fine textures. If colored or textured frames are viewed alone, only flicker is perceived. If the complete sequence is viewed, however, coherent motion is seen. The direction of perceived motion is determined by the stripes that are interpreted as foreground within each frame type. For example, if red stripes are seen as foreground in chromatic frames, and coarse-texture stripes are seen as foreground in texture frames, motion will be perceived to the right: i.e., in the direction that these foreground stripes move (indicated by arrow). This phenomenon argues for a type of motion detection that operates on perceptually defined foreground features, regardless of how they are physically defined.