Abstract
Information complexity of visual displays has become a bottleneck that limits their usefulness. Much of the research in visual complexity has been devoted to what makes a visual pattern complex and how to mathematically model complexity. However, what has been largely neglected in the research is the fact that complexity depends on how the information is intended to be used. Our approach to the complexity problem is to develop complexity measures from the perspective of users' task requirements. Previously we have identified three fundamental complexity factors: quantity and variety of basic information elements, as well as the relation between the elements. In this study, we first determined the generic perceptual tasks involved in using visual displays in time-demanding jobs such as air traffic control. The tasks include: 1) Instantly detecting onset of salient stimuli; 2) quickly and reliably searching for information; and 3) continuously monitoring (reading) text. We then developed three metrics of perceptual complexity based on the three complexity factors and these task requirements. The first metric is the number of fixation groups. A fixation group is defined as the visual stimuli that can be perceived by one fovea fixation. The second metric is the variety of basic visual features such as color, luminance contrast, symbol / texture, and spatial frequency (or size). The third metric is the effect of spatial masking. We experimentally tested these metrics with 20 screenshot images from several air traffic control displays. Eighteen subjects ranked the perceptual complexity of the images from the perspective of the task requirements described above. The subjects also quantitatively estimated the three metrics. The results indicated that all the three metrics were positively correlated with the complexity ranking. Yet, more data are needed to elucidate the mathematically relationship between the perceived visual complexity and individual metrics.