Scene context reduces distractor set-size effects during search
23.3029, Saturday, 16-May, 8:30 am - 12:30 pm, Banyan Breezeway
Arturo Deza1, Emre Akbas1, Miguel Eckstein1; 1University of California, Santa Barbara
Scene context guides eye movements and facilitates search performance (Torralba et al., 2006; Chen & Zelinsky, 2006; Eckstein et al., 2006). Here, we assess how scene context modulates the effect of number of distractors on eye movements and search performance with real scenes. Methods: Observers (64) were presented with 24 grayscale images plus 96 fillers (22.53 deg. x 15.03 deg.) sampled from a dataset of 1224 desk images from multiple viewpoints and varying number of distractor objects. Half the images contained the target (computer mouse). When present, the target appeared in context in 60 % of the images (next to a monitor/keyboard) and out of context in the remaining 40 % (e.g., mouse over monitor). Observers searched for the target from an initial fixation at the edge of the images that was equidistant from mouse in context and out of context locations. Eye position was monitored and the display was randomly terminated after: 1, 2, 3 saccades or a 2 seconds time limit. At the end of each trial, participants performed a 10-scale confidence rating, expressing their certainty of finding the target. Results: Context significantly increased target detection accuracy (p < 0.05) and reduced time to first foveate the target (in context: 900 ms vs. out of context: 1400 ms) across multiple distractors, as well as fixation distance to the target. For the 2 second displays, the detrimental effect of distractors on accuracy (set-size effect) diminished when the target was in context. The temporal dynamics of performance varied across conditions. Additional saccades led to large increases in hit rate for the out of context targets and small for the in context targets. Conclusions: Scene context diminishes the detrimental effect of distractors on search performance in real scenes and alters the temporal dynamics of accuracy increments with subsequent saccades.