Capabilities and limitations of visual search in volumetric images: The effect of target discriminability

In diagnostics, radiologists search for anatomical abnormalities through generated three-dimensional data on flat displays. Professionals are required to scroll repeatedly through image stacks forth and back, as well as remember a broad amount of visual information. This process leads to working memory overload and decreased search outcome. In contrast, a volumetric multi-planar display includes many planes, which makes possible to visualize data in a true physical depth. Thus, theoretically, it can facilitate the visual search performance in diagnostics and lessen the necessity for repeated scrolling. Therefore, our work aims to explore practically the extent to which the visual search is effective, as well as deliver evidence on the scrolling strategy through image stacks when data are shown on many display planes. Visual search set consisted of constant angular size stimuli presented on ten out of twenty display planes in two depth segments. Participants searched for a target with varying target-distractor similarity within trials. All ten images were presented simultaneously in the beginning of each trial and participants scrolled freely through them. In the result, target discriminability affected significantly the correct response rate and time, as well as search behavior was consistent with the physical design of stimuli set. In more detail, the number of moves through image stack almost doubled when the target-distractor similarity increased and, overall, participants skipped searching repeatedly already seen images. The developed visual search task is suggested for implementation in studies of visual perception and search behavior in threedimensional displays.