The benefit of attention is not diminished when distributed over two simultaneous cues.

Abstract

Recent findings have suggested that transient attention can be triggered at two locations simultaneously. However, it is unclear whether doing so reduces the effect of attention at each attended location. In two experiments, we explored the consequences of dividing attention. In the first experiment, we compared the effects of one or two cues against an uncued baseline to determine the consequences of dividing attention in a paradigm with four rapid serial visual presentation (RSVP) streams. The results indicated that two simultaneous cues increase the accuracy of reporting two targets by almost the same amount as a single cue increases the report of a single target. These results suggest that when attention is divided between multiple locations, the attentional benefit at each location is not reduced in proportion to the total number of cues. A consequent prediction of this finding is that the identification of two RSVP targets should be better when they are presented simultaneously rather than sequentially. In a second experiment, we verified this prediction by finding evidence of lag-0 sparing: Two targets presented simultaneously in different locations were reported more easily than two targets separated by 100 ms. These findings argue against a biased-competition theory of attention. We suggest that visual attention, as triggered by a cue or target, is better described by a convergent gradient-field attention model.