Abstract
Previous research has suggested that perceptual grouping may significantly aid performance in Multiple Object Tracking (MOT) tasks. That is, observers may track multiple items by spontaneously grouping disparate items into a single “virtual object”. According to this hypothesis a virtual polygon is initially created and then updated during tracking, with the vertices of the polygon consisting of the tracked elements (Yantis 1992). Recently our lab has demonstrated an ERP component, the CDA, sensitive to the number of successfully tracked items in a MOT task such that the amplitude of the component increases with increasing set size up to the individual subject's tracking capacity (Drew & Vogel 2008 J. Neuroscience). Here, we investigated whether a real or virtual polygon between targets in a tracking task would enhance behavioral performance and reduce tracking load (as indexed by a reduction in amplitude of the CDA). We found that the the presence of actual grouping lines connecting the three targets in a MOT task reduced tracking load when the lines were present as compared to when they were absent. These results suggest that perceptual grouping does indeed play a role in tracking, but this role may be primarily restricted to situations when there are strong bottom-up cues for grouping the objects together.