Abstract
During multiple-object tracking visual attention is allocated asymmetrically across target and distractor objects: probe-detection experiments showed that visual tracking benefits from inhibiting distractors (Pylyshyn, 2006). However, experiments examining multiple-object tracking within 3D-scenes across scene rotations suggest that the spatial relations between all objects may be used in visual tracking (Huff, Jahn, & Schwan, 2009). In the current study, we examined the role of spatial relations among target and distractor objects within 3D-scenes. Participants tracked five of ten balls moving on a circular monochromatic floor-plane. Halfway through each trial, we abruptly rotated only distractors, only targets, or all objects (complete rotations) during a masking flash of 100ms. In control conditions there was a flash but no rotation. If spatial relations between all objects are used in multiple-object tracking, performance should be impaired in conditions with distractor rotation. However, if the distractors are processed separately from the targets and if the relations between distractors and targets are irrelevant for tracking, abrupt distractor rotations should not affect tracking. Additionally, tracking should be easier for complete compared to target only rotations if relations between all objects are used. Compared to the control condition, abrupt distractor rotations impaired tracking performance only in trials in which distractor rotations led to increased crowding around a target object. When distractor rotation involved no increased crowding, tracking performance was comparable to the control condition. Additionally, abrupt complete rotations impaired tracking performance the same way as target only rotations did. Two implications can be drawn from this study. First, there is some evidence that targets and distractors are processed separately. More specific, the spatial relations between targets and distractors seem to be irrelevant for multiple-object tracking. Second, crowding plays an important role for allocating visual attention as crowding around target objects due to distractor rotations impaired tracking.
Deutsche Forschungsgemeinschaft (German Research Foundation) grants HU 1510 4-1 and JA 1761/5-1.