Abstract
Some investigators argue that visual tracking is based on a parallel mechanism, others argue that tracking contains a serial component. In Experiment 1, we put previous theories into a direct test by registering observers' eye movements when they tracked identical moving targets or when they tracked distinct object identities. We found a qualitative difference between these tasks in terms of eye movements. When the participants tracked only position information, the observers had a clear preference for keeping their eyes fixed for a rather long time on the same screen position. In contrast, active eye behaviour was observed when the observers tracked the identities of moving objects. Experiment 2 investigated how observers extract identity information during multiple-identity tracking by adopting the gaze-contingent display technique. We manipulated in real time the presence/absence of the object identities while the participants tracked multiple moving objects. The results showed that when only the identity of the currently foveated object was presented, participants' tracking performance was as good as when the identities of all the objects were presented all the time. Moreover, when identity information was not available when the target was foveated, the performance dropped to the level observed in the condition where the object identities were presented only prior to object movement. The results yield strong support for the view that identity information of multiple moving objects is extracted in a serial manner during identity tracking, whereas the positions of identical moving targets can be tracked in parallel without the need of eye movements.
Meeting abstract presented at VSS 2016