This paper presents evidence that situational awareness in a visualization of data benefits from immersive, virtual reality display technology because such displays appear to support better understanding of the visual information. Our study was designed to deemphasize perceptual and interaction characteristics of the displays and found that the task of counting targets is strongly influenced by the type of system used to render the visualization. Immersive-type displays outperformed traditional monitors. The target objects in the study have distinguishing features that cannot be identified from a distance to alleviate the effect of perceptual differences among displays. Counting was chosen because it entails basic understanding of the relationship among the data values in order to recognize previously counted items. The display choices consisted of a traditional monitor and three configurations of an immersive, projection environment, obtained by selectively turning off one or two pro...