Strategy Shifts in Mixed Density Search

Visual search in an important aspect of many tasks, but it is not well understood how many aspects of layout design affect visual search. This research investigates, with reaction time and eye movement data, the effect of local density on the visual search of structured layouts of words. Layouts were allsparse, all-dense, or mixed. Participants found targets in sparse groups faster even after numerosity effects were factored out, and searched sparse groups before dense groups. Participants made slightly more fixations per word in sparse groups, but these were much shorter fixations. Perhaps most interesting, roughly halfway through searching each mixed layout, participants appeared to switch search strategies with respect to the number of fixations per group of words and fixation duration. When dense groups were searched early in a trial, search strategies were more similar to search strategies in the all-sparse layouts. When searched later in a trial, search strategies were more similar to search strategies of all-dense groups. When combining densities in a layout, it may be beneficial to place important information in sparse groups.