The effects of stimulus-driven competition and task set on involuntary attention

Stimulus Heterogeneity in a Task-Irrelevant Dimension Affects Selective Attention

When multiple stimuli are simultaneously presented, they compete against each other to be represented in the capacity-limited visual system. This competition increases as stimulus heterogeneity increases. Given that selective attention is a way to resolve this competition, it has been known that the effect of attention on task performance is magnified as the level of competition increases due to increased stimulus heterogeneity. While previous studies showed that stimulus heterogeneity in a task-irrelevant dimension affects task performance, it remains unknown how this kind of stimulus heterogeneity interacts with visual attention and stimulus-driven competition. Here, we found that the process of searching for a target stimulus among non-targets became inefficient as stimulus heterogeneity in a task-irrelevant dimension increased. The results also showed that the magnitude of the attentional cuing effect could be affected by increased heterogeneity. However, this modulation was dependent on the type of varied feature or task demand. We suggest that increased stimulus heterogeneity in a task-irrelevant dimension would increase stimulus-driven competition, which impoverishes the quality of stimulus representations.

Cue frequency modulates cuing effect either in the presence or in the absence of distractors

A novel, salient stimulus, even though it is not related to a concurrent goal-directed behavior, powerfully captures people's attention. While this stimulus-driven attentional capture has long been presumed to take place in a purely bottom-up or automatic manner, growing evidence shows that a number of top-down factors modulate the stimulus-driven capture of attention. Recent studies pointed out the cue presentation frequency is such a factor; the capture of attention by a salient, task-irrelevant cue increased as its presentation frequency decreased. Expanding these studies, we investigated how the modulatory effect of the cue frequency differs depending on the level of competition between multiple stimuli. As results, we found that an infrequently presented cue exerted stronger capture effect than a frequently presented cue, either in the presence or in the absence of distractors. Importantly, in the absence of distractors, performance difference elicited by the frequently present cue was due to non-attentional sensory artifacts or decisional noise. However, the same frequent cue evoked genuine attentional effect when multiple distractors accompanied the target, evoking stimulus-driven competition. Taken together, these results demonstrate that the effect of attentional cue is modulated by cue frequency, and this modulation is also affected by stimulus-driven competition.

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.

Opposing effects of memory-driven and stimulus-driven attention on distractor perception

It is well known that a match between working memory contents and a visual stimulus creates attentional bias toward the memory-matching stimulus. The present study investigated whether this memory-driven attentional bias exerts similar effects with conventional, spatial attention driven by a cue stimulus. Specifically, we examined how the effect of a distracting, task-irrelevant stimulus is modulated when attention was oriented toward the distractor in memory- and stimulus-driven manners. The results showed that significant interference by a distractor decreased when attention was allocated to the distractor in a memory-driven manner, whereas the distracter captured attention in a stimulus-driven manner exerted increased interference. By contrast, memory-driven attention brought an unattended stimulus into attentional focus, while stimulus-driven attention failed to do so. These results provide evidence that the mechanisms underlying working memory-driven and stimulus-driven attention are separable, pointing to the dynamic and flexible relationship between working memory and attention.