People are sensitive to distractor motion in multiple object tracking
Rebecca St.Clair & Adriane E. Seiffert
Vanderbilt University

When we track moving objects there are often distracting objects moving among our targets. Previous research leaves open the question whether distractor information is processed during tracking. Although distractors are irrelevant to the tracking task, processing some information about them, such as motion, may prevent distractors from being confused as targets. Our prior research with textured objects suggests that people use motion information to help them track targets (St. Clair, Huff, & Seiffert, 2010, JOV). Tracking objects was worse when the motion of the texture conflicted with the motion of the objects. If distractor motion is used, tracking should be affected by the motion of textures on distractors, regardless of the motion of textures on targets. Observers tracked 3 of 10 textured squares moving linearly and independently in a textured area. The texture in each square moved two times the square's speed either forward, in the same direction as the square, or, backward, in the opposite direction of the square. Texture direction was assigned to targets and distractors independently for a total of four conditions: 1) all squares had forward texture, 2) all squares had backward texture 3) targets had forward texture and distractors had backward texture, and 4) targets had backward texture and distractors had forward texture. Tracking accuracy was higher when targets had forward texture (mean proportion correct M = .79) than when they had backward texture (M = .61; t(18) = 11.13, p<.01), replicating our previous work showing target motion is used during tracking. Similarly, tracking accuracy was higher when distractors had forward texture (M = .72) than when they had backward texture, (M = .68; t(18) = 3.98, p<.01). This suggests that people are sensitive to distractor motion during tracking.