Complexity of Chinese Ideograms is Related to the Number of Sampling Elements

Abstract

Two sets of psychophysical experiments were carried out to find a qualitative measure of the complexity of visual images. The stimuli were 15 Chinese ideograms of the same size. In experiment 1, observers were asked to rate the complexity of images. In experiment 2, for each stimulus the threshold size was determined, defined as the smallest size for which the perceived quality of the image was the same as for large (2 deg) stimuli, ie all details were clearly seen and the stimuli had the same contrast. The measured threshold sizes were in the range 7.9 – 27.6 min arc. Analysing the data further, we found that for some ideograms the sizes of the minimal details (strokes, dots) corresponded to the resolution limit (1 min arc). Some ideograms contained parts with parallel stripes forming quasi-gratings. The distances between stripes at threshold were 1.8 min arc which corresponds to the tuning frequency of the highest spatial frequency channel (Wilson et al, 1983 Vision Research23 873 – 882). The average order of ideograms sorted by degree of complexity was similar to the order according to threshold size. Thus we found a direct correspondence between the complexity of an object and a description in terms of the minimal number of elements needed to preserve the quality of a reduced image. Our results are in agreement with concepts of complexity expressed as a number of details in objects as suggested by Landolt and Snellen, or as a number of spatial-frequency channels as suggested by Ginsburg (1971 IEEE Proceedings 283 – 290).