Navigating complex computer applications has become a critical problem. Understanding what the innate human navigational abilities are and how they relate to specific types of environmental complexity will facilitate the design of assistive devices for the navigation of complex computer applications. Two different techniques for using spatial information to help computer users navigate complex applications have been proposed by the authors. These techniques are derived from studies that have shown how the spatial distribution of information constrains attentional processes in vision. In this project the researchers are undertaking an examination of the relationship between the structure of computer search tasks and the spatial structure of assistance information. They are constructing four computer applications. In two cases the task and guidance information structures are matched in terms of spatial information needs and spatial information presentation, and in the other two they are mismatched. Use of these applications by subjects will be compared on the basis of speed and accuracy. The research is expected to produce a deeper understanding of human-computer task performance under periods of stress and the need for rapid decision-making.