Abstract
A widely known effect of attention on visual processing is the enhancement of perceptual processing at the attended location. When a cue that is informative about the location of a target is presented before it, target perception is enhanced, as reflected by improved identification accuracy. While such effects of voluntary attention on perception are robust, it is unclear whether perceptual processing can also be modulated when a non-informative peripheral cue guides attention involuntarily (Carrasco et al., 2004; Prinzmtal et al., 2005).
We hypothesized that the controversy about the effect of involuntary attention on perception originates from the different stimulus conditions employed across studies. Specifically, studies demonstrating the effect of involuntary attention on perception included distractors with the target, whereas no such distractors were present in studies that reported no effect of attention. It is therefore possible that involuntary attention affects perception only under distractor interference.
We tested this hypothesis in a spatial cuing paradigm. In separate experiments, participants reported the identity of a letter or the orientation of a tilted grating. On any given trial, the target letter or grating could be presented by itself or with distractors of the same stimulus category as the targets. Involuntary attention was guided by a peripheral cue that was non-informative of the target location or identity. We found significant effects of involuntary attention on target identification accuracy only when distractors were present, with no effect of attention without distractors, even when the target was perceptually degraded. These attentional effects were not due to reduced location uncertainty or decision bias because uncertainty of the target location was eliminated by a local mask immediately following the target or by a response cue that indicated the target location at stimulus onset.
These findings suggest that involuntary attention improves perception specifically by resolving target-distractor competition.
NIMH, RO1 MH70776, P30-EY008126 grant to the VVRC.