Precuing an isolated stimulus temporarily outweighs in-stream stimulus facilitation.

The flash-lag effect (FLE), when studied in rapid serial visual presentations, has shown that participants perceived a target presented in a stream prior to its simultaneous out-of-stream replica (T. Bachmann & E. Põder, 2001). In the present study, the authors introduced a precue to the single flashed, isolated target to see if drawing bottom-up attention to the flash also would compensate for the effects of the mechanisms that influence the processing of in-stream items. The extent of the flash-lead effect in the precued condition was considerably larger than the lead-effect in earlier experiments and in a control experiment where no precue was presented for the flashed targets. For the first 200-250 ms from the beginning of the stream, flash-lead dominated. The FLE did not appear until 400 ms after stream onset. The authors interpret results as the combined relative effects of in-stream target masking, in-stream sensory facilitation, and spatial-attentional facilitation.