Relevance-based processing: Little role for task-relevant expectations.

This study examined the role of advance expectations in generating relevance-based selection, using a version of cognitive "blindness" that is driven solely by task relevance. With this irrelevance-induced blindness, participants often fail to report a feature of an irrelevant stimulus, even though the levels of perceptual and cognitive load are minimal (i.e., capacity limitations are not met). Hence, with this phenomenon, selection is based solely on task relevance. In two experiments, we examined such relevance-based selection with a new paradigm in which the participants had to report the location of an object appearing on one of two rings. Critically, while in Experiment 1 the participants could form advance expectations regarding the (ir) relevant stimuli, because the location of the relevant ring and the shape and color of the relevant object were known in advance, in Experiment 2 no concrete advance expectations could be formed. This was established by varying randomly, from trial to trial, the shape, color, and location of relevant and irrelevant stimuli. We found strong irrelevance-induced blindness in both experiments, regardless of whether or not advance expectations were formed. These findings suggest that advance expectations, at least with regard to the task-relevant stimulus' location shape or color, are not necessary for irrelevance-induced blindness to occur; more generally, this implies that such expectations do not play a critical role in selection processes that are based solely on task relevance. We further discuss these findings in the context of Garnerian and Posnerian selection, and their relationship to visual awareness.