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

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.

What processes are disrupted during the attentional blink? An integrative review of event-related potential research

Reporting the second of two targets is impaired when these appear in close succession, a phenomenon known as the attentional blink (AB). Despite decades of research, what factors limit our ability to process multiple sequentially presented events remains unclear. Specifically, two central issues remain open: does failure to report the second target (T2) reflect a structural limitation in working memory (WM) encoding or a disruption to attentional processes? And is perceptual processing of the stimulus that we fail to report impaired, or only processes that occur after this stimulus is identified? We address these questions by reviewing event-related potential (ERP) studies of the AB, after providing a brief overview of the theoretical landscape relevant to these debates and clarifying key concepts essential for interpreting ERP studies. We show that failure to report the second target is most often associated with disrupted attentional engagement (associated with a smaller and delayed N2pc component). This disruption occurs after early processing of T2 (associated with an intact P1 component), weakens its semantic processing (typically associated with a smaller N400 component), and prevents its encoding into WM (associated with absent P3b). However, failure to encode T2 in WM can occur despite intact attentional engagement and semantic processing. We conclude that the AB phenomenon, which reflects our limited ability to process sequential events, emerges from the disruption of both attentional engagement and WM encoding.

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.