Low sensitivity for orientation in texture similarity ratings

Research on visual texture perception in the last decades was often devoted to segmentation and region segregation. In this report, I address a different aspect, that of texture identification and similarity ratings between texture fields with different texture properties superimposed. In a series of experiments, I noticed that certain feature dimensions were considered as more important for similarity evaluation than others. A particularly low ranking is given to orientation. This paper reports data from two test series: a comparison of color and line orientation and a comparison of two purely spatial properties, texture granularity (spatial frequency) and texture orientation. In both experiments, observers tended to ignore orientation when grouping texture patches for similarity and instead looked for similarities in the second dimension, color or spatial frequency, even across different orientations.