Abstract
Objective. People perform better in visual search when the target-defining feature repeats from the previous trial than when it changes across trials, due to automatic intertrial feature priming (IFP). Here, for the first time, we investigated the prevailing idea that IFP is due to stronger automatic capture of spatial attention toward the target when its feature repeats. We measured two effects with the same stimuli: the classic IFP effect during search for feature singletons, and the effect of relative location between an irrelevant singleton and a subsequent probe stimulus that must be discriminated. If the singleton exogenously captures attention, probe performance will be better when its location matches the singleton. If IFP modulates exogenous attention, the relative location effect will be larger when the singleton's color repeats than switches. Method. In each trial we presented a color singleton with either the same or a different color as in the previous trial. A Gabor (probe) followed the color singleton, either at the same or at a different location. The observers' task varied across pairs of trials between a probe and search task ('AABBAABB'). In search trials, observers discriminated the orientation of the singleton. In probe trials, observers discriminated the orientation of the probe. Results. In search trials that followed other search trials, color repetition facilitated singleton discrimination, demonstrating the classic IFP effect. In probe trials, performance was higher when the probe appeared at the same than at a different location as the singleton, demonstrating an exogenous attention shift toward the singleton. Critically, this location effect did not depend on whether the singleton's color repeated or switched from the previous trial. Conclusion. Our results suggest that, contrary to commonly accepted theory, recent experience does not modulate the automatic shift of attention to the target location. IFP and exogenous attention are independent.
Meeting abstract presented at VSS 2016