Abstract
Using a visual search task, we examined the combined effects of overlap and three-dimensional depth on search performance. Participants searched through displays containing opaque polygon targets while their eye-movements were recorded. Half of the participants searched displays with objects presented at different depth planes to one another (the multi-plane condition) and the other half of the participants searched displays with objects presented at a single depth plane (the single-plane condition). As the degree of overlap between objects increased, both RTs and error rates also increased. RTs and error rates were particularly affected when more than two objects could overlap. Adding stereoscopic depth to the images enabled participants to respond more rapidly, though not more accurately, when the level of overlap was high. Eye movement analyses showed a similar pattern for overlap, with increasing fixation durations, increasing number of fixations, and increasing total fixation time as the level of overlap increased. Stereoscopic depth reduced the total time spent fixating regions containing many overlapping objects, suggesting that depth aided in object segmentation and recognition processes. These results have implications both for current models of visual search, which have not yet explored the role that overlap and depth together can play in modulating search behaviour, and for real-world search tasks that contain overlapping objects, such as airport X-ray screening and radiography.
Meeting abstract presented at VSS 2014