Abstract
When a context motion is perceived in a particular direction (e.g., to the right), its effect on motion perception in that direction depends on whether motion sensitivity is tested “in front of” (i.e., to the right of) or “behind” (i.e., to the left of) the context motion (VSS,2004). For some subjects, the spatial anistropy entailed more excitatory influence on a test motion “in front of” the context motion than “behind” it. For other subjects, the spatial anistropy entailed less inhibition on the test motion “in front of” the context motion than “behind” it. It has been found, in addition, that attention can modify the extent to which interactions among collinear motions are excitatory or inhibitory. Interactive influences from the context stimulus are less excitatory (or more inhibitory) when attention is focused between the two locations of the test stimulus than when it is spread across the two locations. This result indicates that the effect of attention on motion perception is non-local; it extends far beyond the region where the perceiver is attending. That is, even though attention spread is manipulated in the region of the test stimulus, it affects interactive influences emananting from motion at other spatial locations.