SSC San Diego TR 1890, August 2002

Approved for public release; distribution is unlimited. Reducing the clutter on geographical displays should help military decision-makers manage their attention and concentrate on the most important or threatening tracks. This report presents a study that considered the question of how the decluttered tracks should be represented. The declutter symbols must simultaneously reduce distraction while still supporting situation awareness. We used a visual search task to evaluate six declutter symbologies. The symbologies were created by manipulating two factors, symbol type and coloring. The symbol types were relatively complex MIL–STD–2525B symbols that coded substantial information about the tracks, simplified outlines of ships and aircraft that coded an intermediate amount of information, and simple dots that coded minimal information. The coloring factor consisted of using either faded versions of the MIL–STD–2525B colors or using gray. We also investigated the effect of different amounts of declutter, from no declutter to 25% declutter, 50% declutter, and 75% declutter. The participants were 52 undergraduate students from local universities. Participants searched for two target symbols among a field of 48 symbols that were a mixture of fully visible, brightly colored MIL–STD–2525B symbols and decluttered symbols. The targets always appeared among the fully visible symbols, and the decluttered symbols merely served as distracters. Each increase in the amount of declutter produced a significant and linear drop in search time. The intermediately complex symbol outlines produced the least distraction and the fastest search times, but the differences among symbol types were small. Surprisingly, the faded colored symbols produce as little distraction and as fast search times as the gray symbols. We concluded that the faded, colored MIL–STD–2525B declutter symbols are the best declutter symbols because they are little more distracting than the alternatives while providing much more information. The next step will be to determine how well these declutter symbols help decision-makers manage their attention under more realistic conditions. Figures 1. Cluttered geographical display (left) and same display in which less threatening tracks have been decluttered by fading their symbols (right). 2. Six declutter symbologies and their hypothetical effects on situation awareness and distraction. The yellow symbol at top is a fully visible MIL–STD–2525B symbol .. 3. Four screenshots of experimental display: no declutter (upper left), 25% declutter using gray Symbicons (upper right), 50% declutter using faded MIL –STD–2525B (lower left), and 75% declutter using gray dots (lower right). 4. Time taken to find both targets on each trial. …