Visual Search Asymmetries in Heavy Clutter: Implications for Display Design

Objective: An experiment aimed to test whether design of symbology to produce visual search asymmetries might facilitate target detection in cluttered displays. Background: A visual search asymmetry exists between two stimuli when a target of one type is found efficiently among distractors of the second type but a target of the second type is found with difficulty among distractors of the first type. Asymmetries have generally been studied within relatively sparse displays. In the present study, the authors tested whether an asymmetry driven by stimulus familiarity persists within heavily cluttered imagery. Method: In this study, 10 participants performed a visual search task using stimuli (canonical vs. reversed Ns) known to produce a search asymmetry. Search stimuli were embedded within geospatial images containing either low or high levels of clutter. A decision theoretic index of sensitivity served as the dependent measure. Results: The search asymmetry was robust against the presence of heavy display clutter. Specifically, sensitivity was greater when the target was a reversed N rather than an N, and this pattern remained within cluttered displays. Time-accuracy analysis revealed that the search asymmetry increased the rate of information accumulation roughly equally within low-and high-clutter images. Conclusion: Search asymmetries are robust against heavy, spatially continuous visual clutter. Application: Design of display symbology to produce visual search asymmetries can offset the costs of visual clutter, maximizing detectability of task-critical information in complex displays.