Abstract
We previously designed a self-splitting image comprising two intersecting and orthogonal gray bars (45-deg vs. 135-deg) with the same luminance (VSS 2017). When rendered in motion, the orthogonal bars were alternately seen in front (modal surface) and in back (amodal surface). This design paradigm allowed us to show that when the two bars have different widths, the wider bar was seen over a longer duration as the modal surface, in accordance with Petter's rule. One explanation for the rule is that the gap interval to interpolate is smaller for the wider bar, which endows it with a stronger tendency to integrate as a modal surface. To extend this explanation here, we examined the condition where both orthogonal bars were seen as amodal surfaces. This was achieved by using a red diamond-shaped occluder (0.8 x 0.8-deg) to cover the intersection of the orthogonal gray bars as they moved over one another. The bars had different widths (0.3 vs. 0.6-deg). We found that this arrangement resulted in observers seeing the two bars as amodal surfaces alternating in depth behind the diamond occluder. And importantly, the wider bar enjoyed a higher predominance of being seen on top of the thinner bar. Thus, our finding extends Petter's rule to overlapping amodal surfaces. We then modified the display by making the two bars the same width (0.3-deg) but with different contrast values (10% vs. 31.6%). We found that this caused the amodal bar with the higher contrast to be seen on top more frequently. This suggests high contrast increases the tendency for surface integration and causes it to seen on top. Altogether, our results support the general notion that surface integration tendency is an important factor in determining perceived depth order between perceptually interpolated surfaces, no matter whether they are modal or amodal surfaces.
Meeting abstract presented at VSS 2018