Two task-relevant streams of characters (immediately to the left and right of central fixation) were flanked by task-irrelevant streams. In the cued-attention condition (illustrated here), uniquely red stimuli (‘L’ and ‘R’, corresponding to left and right, respectively) cued participants either to shift attention to the other stream (e.g., an R cue appearing in the left stream) or to hold attention on the currently relevant stream (e.g., an R cue appearing in the right stream). Participants indicated the identity of targets (digits) appearing within the currently attended stream. In the uncued-attention condition, cues were omitted; participants were to shift attention between the relevant streams occasionally and at will. In both conditions, digits occurred only rarely, and they appeared simultaneously in both the left and right streams.