Perceived motion in the vector sum direction.

The visual system is known to extract both Fourier (e.g. contour) and non-Fourier (e.g. texture boundary) motion signals from moving patterns. Recent evidence suggests that both Fourier and non-Fourier motion signals are involved in the analysis of rigid two-dimensional image motion. To determine how these signals are combined, we have measured perceived directions for plaids composed of either two non-Fourier components or one Fourier plus one non-Fourier component. In all cases the visual system combines these components to produce perceived motion in the vector sum direction, even when this deviates by as much as 53 deg from the intersection of constraints direction. This result was predicted by a model for pattern motion that combines Fourier and non-Fourier component motion signals using a vector sum operation.