| |
Abstract:
Spatial attention can bias visual processing, leading to
better perception of attended targets relative to unattended
distractors. Biased competition models suggest that the role of
attention is to protect target processing from the effects of
distractor interference (i.e., distractor exclusion). In line with
these models, previous research has shown that spatial attention
effects are larger when distractors are presented than when they
are not. The present research extends this account by showing that
the level of distractor exclusion depends not just on whether
distractors are present or absent, but also on whether distractors
are likely to occur. Subjects reported the identities of two target
digits from either attended or unattended locations. We also
manipulated the probability that distractors would appear in the
locations surrounding the target stimuli. In high noise blocks, 80%
of the trials contained distractor stimuli, while in low noise
blocks only 20% of the trials contained distractor stimuli. We
found that spatial cueing effects were significantly larger when
distractor interference was expected than distractors were not
expected, even when performance was compared between identical
stimulus displays. While it is clear that observers have top-down
control over which locations are attended, our results suggest that
there is also top-down control over the degree of distractor
exclusion during high and low noise contexts.
|
