Facilitation of shape-from-shading perception by random textures

Most natural objects have a texture on their surface, so the segregation between shading and texture is crucial for the robust perception of three-dimensional structure: The visual system has to decide whether shading or texture evoked the luminance change. We found that the contextual pop-out that results from shading was not suppressed, but was even facilitated, when random texture was added to the luminance of the entire stimulus, indicating the functional segregation and facilitative interaction between shading and texture cues. The local contrast evoked by random texture within a figure or at a boundary was a major factor in the facilitation, suggesting the crucial role of early vision in the interaction between the cues.