Depth stratification in illusory-contour figures on heterogeneous backgrounds is independent of contour clarity and brightness enhancement.

Depth stratification in illusory-contour figures was studied by superimposing Kanizsa figures on heterogeneous backgrounds. Gaussian-noise textures were employed in two rating-scale experiments to explore observers' judgments of (i) illusory-contour clarity, (ii) brightness enhancement, and (iii) depth stratification. In experiment 1, depth stratification was found to be stronger in heterogeneous conditions. In experiment 2, texture coarseness was manipulated to determine how depth stratification is affected by linear elements of different sizes in the background, and to relate the variation to contour clarity and brightness enhancement. Results suggest that depth stratification is independent of contour clarity and brightness enhancement. Preliminary novel observations on illusory-contour formation are reported.