In a series of four experiments using rapid serial visual presentations of
two target letters embedded in numeral distracters, with different numbers
of display positions and with or without masking, we show that (1) the nonm
onotonic, Ii-shaped attentional blink (AB) function, which occurs when all
items are presented at the same display location, is eliminated in favor of
a monotonic function when targets and distracters are presented randomly d
ispersed over four or nine adjacent positions; (2) the AB monotonicity is m
aintained with the spatially distributed presentation even when backward ma
sks are used in all possible stimulus positions and when the location of th
e next item in sequence is predictable; and (3) the U-shaped AB is not due
to position-specific forward or backward masking effects occurring at early
levels of visual processing. We tentatively conclude that the U-shaped AB
is primarily a function of the interruption of late visual processing produ
ced when the item following the first target occurs at the same location. I
n order for the AB to severely disrupt performance, the item following the
first target must be presented at the same location as the target so that i
t can serve both as a distracter and as a mask interrupting or interfering
with subsequent visual processing.