Abstract
Observers can visually track multiple independently moving target objects among identically looking distractor objects (e.g., Pylyshyn & Storm, 1988). Experiments examining multiple object tracking within three-dimensional scenes demonstrate that while smooth scene rotations do not affect tracking performance (Liu et al., 2005) abrupt scene rotations yield tracking more difficult but not impossible (Huff, Jahn, & Schwan, 2009). We report three experiments examining the mechanisms involved in successful tracking of three target objects across abrupt scene rotations by recording observers' eye movements. In addition to the target and distractor objects we analyzed eye movements towards the invisible centroid of the target configuration as suggested by previous research (Fehd & Seiffert, 2008). The centroid is less displaced by scene rotation than the target objects and the centroid moves slower than the target objects thus being a stable reference for the target set. With our first experiment, we demonstrated a significant drop of gaze time spent on the target objects but not the centroid for 500ms following an abrupt scene rotation. Distractor objects were irrelevant for explaining the eye movement data. The second experiment replicated these findings and extended them by showing increasing centroid looking with increasing object speed. With our third experiment, we replicated and therefore reinforced our previous findings using an eye-tracker with 500Hz that had a higher spatial and temporal resolution than the eye-tracker with 50Hz that we used in experiments one and two. Summarizing, we show that observers take advantage of the higher stability of the centroid of the target configuration when tracking multiple target objects in displays with abrupt scene rotations or increasing object speed.
Deutsche Forschungsgemeinschaft (German Research Foundation) grants HU 1510 4-1 and JA 1761/5-1.