Spatial Attention Can Be Allocated Rapidly and in Parallel to New Visual Objects

In real-life visual environments, where multiple objects compete for processing, new objects that require immediate attention often appear when attention is already focused elsewhere. The question of whether spatial attention can be directed independently to different locations in the visual field remains controversial. Serial models assume a unitary attentional focus that is directed to one object at a time and moves rapidly between objects. According to parallel models, attention can be simultaneously allocated to several visual objects, but the distribution of attention cannot change rapidly when new objects arrive. Here we demonstrate the existence of a fast and flexible mechanism of attentional object selection, where focal attention is allocated in parallel and independently to different target objects. Using event-related brain potential (ERP) markers of visual attention, we show that when two targets appear in rapid succession at different locations, two separate foci of attention are established, each with its own independent time course. Attention can be maintained at its previous location while it is simultaneously allocated to a new target object. Our results challenge the view that the attentional focus is always unitary and that the spatial selection of multiple visual objects operates in a strictly serial fashion.