SPLTRAK Abstract Submission
Quantification of the self-motion load on multiple object tracking: How many objects are you worth?
Adriane E. Seiffert, Laura Thomas
Department of Psychology, Vanderbilt University

Perhaps walking and chewing gum is effortless, but walking and tracking moving objects is not. Keeping track of moving targets among moving distractors is impaired by walking from one location to another, suggesting that updating location of the self puts demands on object tracking processes (Thomas & Seiffert, 2010, Cognition).  Here, we quantified the cost of self-motion in terms of the tracking load.  Participants in a virtual environment tracked a variable number of targets (1-5) among distractors while either staying in one place or moving along a path that was similar to the objects' motion. At the end of each trial, participants decided whether a probed dot was a target or distractor.  As in our previous work, self-motion significantly impaired performance in tracking multiple targets (F(4,52)=39, p<.001).  Accuracy of tracking 3 targets while moving (86% correct) was similar to tracking 4 targets while staying (85%, t<1, ns), but significantly better than tracking 4 targets while moving (79%, t(13)=3.7, p<.005) which was similar to tracking 5 targets while staying (81%, t<1, ns).  Quantifying tracking capacity (K) under the two conditions and fitting the results to an asymptote revealed that self-motion during tracking produced a cost to capacity of about 0.8 objects.  Tracking your own motion is worth a little less than one object, suggesting that updating the location of the self is similar, but slightly easier, than updating locations of objects.