The perceptual enhancement by spatial attention is impaired during the attentional blink.

A salient, but task-irrelevant stimulus has long been known to capture attention in an automatic, involuntary manner. However, the automaticity of involuntary attention has recently been challenged. While some studies showed that the effect of involuntary attention depended on top-down attentional resources, other studies did not. To reconcile this conflict, we suggest to consider that attentional effect is not homogenous. Specifically, we hypothesized that the dependence of involuntary attention on top-down attention interacts with the presence/absence of the target location uncertainty and distractor interference. Consistent with this hypothesis, we found that when the attentional resources were depleted, the involuntary attention did not affect the perception of a single target stimulus (Experiment 1). However, when the target was accompanied by multiple distractors, evoking uncertainty regarding the target location, the involuntary attentional effect was observed, regardless of the availability of attentional resource (Experiment 2). This was so, even when the target location was always marked by a response cue, minimizing the target location uncertainty (Experiment 3). These findings provide a reconciliation for the theoretical debate regarding the dependence of involuntary attention on top-down attention and clarifies how perception is modulated by involuntary attention.