Abstract
In multiple object tracking (MOT) tasks participants are typically asked to keep track of a set of target items presented among identical distractors as they move around a display. Typically, participants perform this task accurately when tracking up to about four items. Although the object-based nature of this tracking ability has been demonstrated in a variety of ways, it may be that spatial attention also plays a role. The current work used the N1 component of the human event-related potential (ERP) to determine if spatial attention is preferentially allocated to target items during MOT. Participants tracked two of four objects as they moved around a display. In order to measure ERPs, probes (i.e. white flashes) were presented randomly on targets, distractors, or the background. Since the amplitude of the N1 is known to be affected by the allocation of spatial attention, we reasoned that if spatial attention tracks objects during MOT then probes presented on target items should produce larger amplitude N1s than probes presented on distractors or background locations. In accordance with this prediction, we observed larger amplitude N1s for target probes, but this effect was only reliable at electrode locations over the left hemisphere for probes presented in the right (contralateral) visual field. These results, at least in part, support the idea that spatial attention may be used to track objects during MOT. They also suggest that the left hemisphere may be particularly important in MOT.