Abstract
In the present study, we investigated temporal development of attentional set in a task in which observers identify a target letter among sequentially presented nontarget letters. Specifically, we examined whether attentional set can be fully established at the beginning of a trial or whether the set develops gradually within a trial. We manipulated the time from the onset of a trial to a target and the presence or absence of peripheral distractors as an index of fidelity of attentional set. We focused on the effect of feature search mode because previous study had shown that of singleton detection mode (Inukai & Kawahara, 2011). Participants identified a target letter of a specific color (e.g., red) embedded in a stream of rapidly presented nontargets of heterogeneous color while ignoring peripheral distractors. Baseline accuracy when no peripheral distractor was presented increased as the target appeared later in the stream, suggesting attentional awakening. Identification accuracy was impaired by the presence of peripheral distractors (i.e., attentional capture) early in the stream when observers adopted the feature search mode. The magnitude of attentional capture increased to over 1,000 ms under the singleton detection and feature search modes. The result that the magnitude of attentional capture was affected by the temporal position of the target under the two search modes suggests that attentional set develops gradually during the search for a target regardless of search strategy. Importantly, the result that attentional capture occurred early in the stream only under the feature search mode suggests that the fidelity of attentional set was higher under the feature search mode than that under the singleton detection mode at the start of a trial. Such a difference may be because establishing the feature search mode would be a benefit during successive visual search trials.
Meeting abstract presented at VSS 2015