Abstract
To study the role of memory in search, researchers have used abstract displays that lack the richness and spatial structure of natural scenes, potentially limiting the influence of memory on search. In the present study, a new method was developed to examine memory in visual search over natural scenes. On each trial, participants viewed a scene for 10 s (preview scene), followed by a target object at fixation (target probe), followed by a search scene, which was the same scene as used in the preview. The target object was always present in the search scene, and it was either identical to the target probe or mirror reversed. The task was orientation discrimination, which required finding the target in the search scene. Reaction time and eye movement measures of search efficiency were collected. Three preview conditions examined the role of memory in visual search. In the target-present preview condition, the target object was present in the preview scene at the same position as it would appear during search (target orientation in preview and search scenes was uncorrelated). Efficient search in this condition would indicate that memory for object position can guide search through a scene. In the target-absent preview condition, the target was absent from the preview. Efficient search in this condition would indicate that memory for general scene structure can guide search. Finally, a no-preview control condition established baseline search efficiency. Search was highly efficient in the target-present preview condition. Mean delay between search scene onset and target fixation was less than 400 ms. Typically, the first saccade during search was directed to the target. Search took significantly longer in the target-absent preview condition but was more efficient than search in the no preview condition. These data demonstrate that memory for the absolute positions of objects and memory for general scene structure have strong influences on the efficiency of visual search.
This research was supported by NIH grant R03 MH65456.