Detecting minelike targets: synergistic effects of correlated and uncorrelated sensor channels

We report results from an experiment designed to study the perceptual and learning processes involved in the detection of land mines. Subjects attempted to identify the location of spatially distributed targets identified by a sweeping a cursor across a computer screen. Invisible screen 'objects' were identified by either tones (A) or clicks (B) or both. Objects defined by a tone or a click only are distracters; the single object defined by both is the target (mine). We looked at the effect on target detectability of the number and spatial distribution of distracters. As expected from theoretical analysis, target detectability was highest when A and B distracters were negatively correlated; lowest when they were positively correlated. Under these conditions, detectability is was also inversely related to the number of A distracters (which were spatially diffuse) but was largely unaffected by the number of B distracters (which were punctate). Adding a second sensor channel greatly enhanced target detectability, especially if A and B distracters were spatially uncorrelated or negatively correlated.