Abstract
Selection from a stream of visual information can be elicited via the appearance of a cue. Cues are thought to trigger a time-consuming deployment of attention that results in selection for report of an object from the stream. However, recent work using rapid serial visual presentation (RSVP) of letters finds reports of letters just before the cue at a higher rate than is explainable by guessing. This suggests the presence of a brief memory store that persists rather than being overwritten by the next stimulus. Here, we report experiments investigating the use of this buffer and its capacity. We manipulated the number of RSVP streams from 2 to 18, cued one at a random time, and used model-based analyses to detect the presence of attention shifts or buffered responses. The rate of guessing does not seem to change with the number of streams. There are, however, changes in the timing of selection. With more streams, the stimuli reported are later and less variable in time, decreasing the proportion reported from before the cue. With two streams - the smallest number of streams tested - about a quarter of non-guess responses come from before the cue. This proportion drops to 5% in the 18 streams condition. We conclude that it is unlikely that participants are using the buffer when there are many streams, because of the low proportion of non-guesses from before the cue. Instead, participants must rely on attention shifts.