Multiple object tracking disrupts feature binding in visual working memory

Abstract

One important aspect of visual perception is the ability to bind together different visual features into a coherent object percept. We are also able to maintain a limited number of such bound objects in visual working memory (VWM). While it is widely believed that attention plays a necessary role in perceptual feature binding, it is unclear whether attention also plays a role in maintaining bindings in VWM. Contrary to the view that attention is necessary for VWM binding (Wheeler & Treisman, 2002), studies that have combined VWM and attention in a dual-task procedure have failed to show that engaging attention disrupts binding (Allen, Baddeley, & Hitch, 2006; Yeh, Yang, & Chiu, 2005). However, previous work may not have used sufficiently demanding visual attention tasks. To further test the attentional requirements of VWM binding, we gave participants a 6 second long attentive tracking (multiple object tracking, MOT) task during a VWM retention interval. The effect of the MOT task on VWM performance was assessed in different blocks of trials that required either color, shape, color or shape (Unbound), or color and shape (Bound) VWM. The results revealed that MOT severely disrupted binding in VWM: Dual-task costs in VWM performance were significantly larger in the Bound condition than in all the other conditions, including the Unbound condition. A second experiment indicated that the disruptive effect of the MOT task originated from the attentional demands of tracking: When participants performed a secondary task similar to the MOT task except that the items remained static, Bound VWM was not significantly impaired. These results suggest that attention plays a role in maintaining binding in VWM.