Dividing attention between two different categories and locations in rapid serial visual presentations

When two targets are embedded in a rapid serial visual presentation (RSVP) stream of distractors, perception of the second target is impaired if the intertarget lag is relatively short (less than 500 msec). This phenomenon, called attentional blink, has been attributed to a temporal inability of attentional resources. Nevertheless, a recent study found that observers could monitor two RSVP streams concurrently for up to four items presented in close succession, suggesting a much larger visual capacity limit. However, such high-capacity performance could be obtained by a rapid shift of attention, rather than concurrent monitoring of multiple locations. Therefore, the present study examined these alternatives. Results from six experiments indicate that observers can concurrently monitor two noncontiguous locations, even when targets and distractors are from different categories, such as digits, English alphabet letters, Japanese characters, and pseudocharacters. These results can be explained in terms of a modified input-filtering model in which a multidimensional attentional set can be flexibly configured at different spatial locations.