Spatiotemporal frequency characteristics of the visual unpleasantness of dynamic bandpass noise

Recent psychophysical evidence shows that visual discomfort and unpleasantness are related to particular image features such as the spatial frequency and orientation spectrum. We also have a strong unpleasant feeling toward moving objects such as swarming worms, but it is poorly understood how motion information relates to a feeling of unpleasantness. The present study investigated spatiotemporal frequency characteristics that cause visual unpleasantness using bandpass noise with variable spatial frequencies, temporal frequencies, temporal frequency bandwidths, and orientation bandwidths. Results show that dynamic noise with relatively low temporal frequencies (0.5-2 Hz) was markedly more unpleasant than static noise, including that judged as the most unpleasant in a previous study. Remarkably, translational motion of the noise did not increase the feeling of unpleasantness. A subsequent experiment using a dynamic texture in which elements moved in a variable range of random directions showed that the variegated motion direction plays a critical role in promoting visual unpleasantness. Natural scenes have regularity in that features inside an object usually move in the same direction and rarely at random, and the present results further support the notion that deviation from the statistical regularity of natural scenes in images and movies induces negative emotions.