Abstract
If movement is seen in a discrete part of a static background, it is likely to result from physical motion behind an opening, possibly covered by a neutral or colored transparency. In this situation, color transparency is perceived despite the absence of X-junctions. Therefore we tested if motion information alone is sufficient to invoke scission between surface and transparency colors, by using 280 spectrally selective surface reflectances and 6 spectrally selective transparent filters. First we quantitatively compared scission from motion to scission from X-junctions. Perceived colors of the transparent overlay and the opaque overlaid surfaces were similar under motion generated color transparency and transparency from the same filter moving on a static version of the same background, demonstrating the power of motion per se to invoke color scission. Next we found that motion generated color scission was incomplete by comparing overlaid surface colors under motion-generated transparency to exposed background surfaces, and to exposed surfaces of the same chromaticity as the overlaid surface. The perceived color of overlaid surfaces could be modeled as resulting from spectral filtering followed by the counteracting effect of lateral induction from adjacent areas under the filter. As a control, we also compared the two situations when the surround was completely dark. Under this condition, the moving filter is seen as a spotlight, and its perceived color has previously been shown to be a result of spatial integration, not scission. The moving background behind the static filter could also be interpreted as under a static spotlight. Perceived overlays and overlaid surfaces again appeared similar under the two conditions. We conclude that motion alone is sufficient to evoke percepts of color transparency that are indistinguishable from simulations of moving transparent filters. Color transparency perception thus corresponds to multiple physical conditions and does not require the presence of X-junctions.