Simultaneous cueing at two discrete locations and lag-0 sparing: breaking the attentional spotlight
32.24, Sunday, May 12, 10:45 am - 12:30 pm, Royal Ballroom 4-5
Brad Wyble1, Maxwell Bay2; 1Department of Psychology, Pennsylvania State University, 2Department of Neurology, UCLA
Visual attention is frequently described as a spotlight that can focus on one location to the exclusion of others, and there are hundreds of experiments that support variations of this theory. However, like Newtonian mechanics, a description of a system that is sufficient at one scale can break down at a finer scale, revealing a more fundamental mechanism. Here, we show that cueing benefits can be triggered simultaneously at two locations without affecting the intervening region of the visual field provided that the cues are simultaneous. Participants viewed 4 concurrent RSVP streams, searching for two simultaneous letter targets among digit distractors. Cues were red lines presented above and below a cued stream. The size of the cueing benefits from two simultaneous cues on both targets was large enough that we can discount a mixture model explanation in which attention is sometimes present at one location and sometimes at the other but never both (see supplement). These effects were similar regardless of whether or not the two targets were in the same hemifield. In further support of simultaneous attention to two locations, we found in a second experiment that two targets are perceived more often when presented simultaneously than when offset by 100-300ms. These results are well explained by a gain-field theory (Cheal, Lyon & Gottlob 1994) in which the state of attention can vary at each location across the visual field. In this model, attention does not reside at any one location but can be active at multiple locations simultaneously. Two simultaneous cues or targets can evoke attention at two locations. However, if one target is given a 100ms headstart over a second target, the attentional focus collapses around that first target, producing behavior consistent with a unitary spotlight of attention.