A note about preferred orientations at the first and second stages of complex (second-order) texture channels

Complex (second-order) channels have been useful in explaining many of the phenomena of perceived texture segregation. These channels contain two stag es of linear filtering with an intermediate pointwise nonlinearity. One una nswered question about these hypothetical channels is that of the relations hip between the preferred orientations of the two stages of filtering. Is a particular orientation at the second stage equally likely to occur with al l orientations at the first stage, or is there a bias in the "mapping" betw een the two stages' preferred orientations? In this study we consider two p ossible mappings: that where the orientations at the two stages are identic al (called "consistent" here) and that where the orientations at the two st ages are perpendicular ("inconsistent"). We explore these mappings using a texture-segregation task with textures composed of arrangements of grating- patch elements. The results imply that, to explain perceived texture segreg ation, complex channels with a consistent orientation mapping must be eithe r somewhat more prevalent or more effective than those with an inconsistent mapping. (C) 2001 Optical Society of America.