One of the unique applications of Mixed and Augmented Reality (MR/AR) systems is that hidden and occluded objects can be readily visualized. We call this specialized use of MR/AR, Obscured Information Visualization (OIV). In this paper, we describe the beginning of a research program designed to develop such visualizations through the use of principles derived from perceptual psychology and cognitive science. In this paper we surveyed the cognitive science literature as it applies to such visualization tasks, described experimental questions derived from these cognitive principles, and generated general guidelines that can be used in designing future OIV systems (as well improving AR displays more generally). Here we also report the results from an experiment that utilized a functioning AR-OIV system: we found that in a relative depth judgment, subjects reported rendered objects as being in front of real-world objects, except when additional occlusion and motion cues were presented together.