Abstract
Purpose. In Multiple Object Tracking (MOT), subjects follow a flashed subset of identical visual objects that move independently about a display. It is known that under some conditions it is possible to track objects even when they completely disappear from view (e.g. Scholl and Pylyshyn (1998)). Our primary aim in this study is to examine whether tracking mechanisms are predictive, and, in particular, whether subjects track better when objects reappear at a location predicted by their trajectories rather than at some other location, such as at the location at which they disappeared. A secondary aim is to see for how long objects can disappear without significantly interfering with tracking. Methods. Four of eight objects momentarily flash, and subjects are asked to track the flashed objects for 5 seconds. Midway into each trial, all objects on the screen disappear and reappear either a) at point of disappearance (“non-move” condition); or b) at a position consistent with trajectory (“move” condition). Three disappearance intervals were used: 150ms, 300ms, and 450ms. Results. Subjects tracked better in the non-move condition than in the move condition for all disappearance durations. For the move condition subjects tracked best in the shortest disappearance interval and worst in the longest. There was no significant difference between performance at the different disappearance durations for the non-move condition. Conclusion. The main conclusion suggested by this experiment is that objects are not tracked predictively for disappearance durations we have examined (up to 450 ms). Subjects appear to only keep track of where objects disappear and not where they are likely to reappear.