Abstract
The question of whether or not figure-ground segmentation can occur without attention is unresolved. Many traditional theories assumed it could, but the evidence is scant and open to alternative interpretations. Recent research indicating that exogenous attention can influence figure-ground segmentation raises the question anew. We tested this question by asking participants to perform a change-detection task on a small target matrix made up of random black and white pixels. When different, only a single pixel changed, rendering the task sufficiently demanding to absorb attention. The target matrix was presented on a task-irrelevant scene of alternating regions organized into figures and grounds by convexity. Independent of any change in the target matrix, the figure-ground organization of the scene backdrop changed or remained the same. The edges in the scene backdrop always changed across successive displays, regardless of whether or not figure-ground organization changed, to control for the possibility that a change in scene organization could be detected from local changes in edges per se. Changes in scene figure-ground organization produced congruency effects upon speed and accuracy of the target-change judgments. These effects arose despite inattentional blindness to the scene backdrop. When probed with surprise questions, participants could report neither the figure-ground status of the region on which the target appeared in the preceding display or whether the figure-ground organization of the scene had changed on the preceding trial. When attending to the scene backdrop, participants made these reports highly accurately. These results clearly demonstrate that figure-ground segmentation can occur without focal attention.