Is There a Pop-Out of Exclusively Binocular (Cyclopean) Contours and Regions?

In this work, contours and texture regions were designed so that they could not be observed by either eye alone, but only after images from both eyes were fused into a single stereoscopic picture. Two planes of random dots were positioned one in front of the other so that their random-dot patterns were transparently overlaid. In this way the dot pattern in the front plane was completely masked by the dots in the back plane for either eye on its own. Such exclusively binocular or ‘cyclopean’ stimuli are therefore defined by a conjunction of depth information with other basic visual features. It is shown that, unlike their monocular counterparts, cyclopean contours do not pop-out. It is also shown that cyclopean regions pop-out only when they have either much higher or much lower luminance contrast than their surroundings, or (for some observers) when the cyclopean region is defined by motion contrast. Colour, luminance-contrast sign, and orientation-defined regions are not easily detected even when viewed attentively.