A LINEAR-SYSTEMS APPROACH TO THE DETECTION OF BOTH ABRUPT AND SMOOTH SPATIAL VARIATIONS IN ORIENTATION-DEFINED TEXTURES

Two distinct paradigms have characterized most previous studies of tex ture perception: one has dealt with texture segregation, the other wit h the processing of texture gradients. Typically, studies of texture s egregation have used stimuli with abrupt textural variations, whereas studies of texture gradient processing have used stimuli with smooth t extural variations, In this study we have asked whether the mechanisms which process abrupt and smooth textural variations are the same, by considering whether a simple linear model can account for the detectio n of orientation modulation in micropattern-based textures with three types of modulation: sine-wave (SN), square-wave (SQ) and missing fund amental (MF). The MF waveform was constructed by removing the fundamen tal harmonic from a square-wave. We found a clear overall ordering of sensitivity: SQ > SN > MF, We found that sensitivity to the SQ and MF stimuli could be predicted very well from the SN data if one assumed t hat the r.m.s. output of a single linear channel underlay the detectio n of the orientation modulation, This suggests that the detection of b oth abrupt and smooth changes in orientation-defined textures is subse rved by a common mechanism which mimics the operation of a single line ar channel.