DISCRIMINATION OF ORIENTATION-DEFINED TEXTURE EDGES

Preattentive texture segregation was examined using textures composed of randomly placed, oriented line segments, A difference in texture el ement orientation produced an illusory, or orientation-defined, textur e edge. Subjects discriminated between two textures, one with a straig ht texture edge and one with a ''wavy'' texture edge. Across condition s the orientation of the texture elements and the orientation of the t exture edge varied. Although the orientation difference across the tex ture edge (the ''texture gradient'') is an important determinant of te xture segregation performance, it is not the only one. Evidence from s everal experiments suggests that configural effects are also important . That is, orientation-defined texture edges are strongest when the te xture elements (on one side of the edge) are parallel to the edge, Thi s result is not consistent with a number of texture segregation models including feature- and filter-based models, One possible explanation is that the second-order channel used to detect a texture edge of a pa rticular orientation gives greater weight to first-order input channel s of that same orientation.