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Abstract:
Abstract: We examined endogenous and exogenous cueing using
the Egly, Driver & Rafal (1994) paradigm to investigate the
effects of objects on spatial attention. In one experiment, two
black lines were presented in place of the two rectangles used by
Egly et al., eliminating the property of closure. A cue appeared at
the end of one of the lines followed by a target at one of three
locations: the cued location (valid), different location within the
same line (invalid-within), or equidistant in the opposite line
(invalid-between). At the short stimulus onset asynchrony (SOA),
cues were 75% predictive of target position; at the long SOA, cues
were non-predictive (33% at each position). As expected, endogenous
cueing at the short SOA produced facilitation, while exogenous
cueing at the long SOA produced inhibition. Unlike Egly et al., we
found no differences between within- versus between- object
conditions, either for facilitation or inhibition. In another
study, we added background structure to the display making the same
two black lines appear as distinct elements of a scene. When this
structure was present, the results replicated those of Egly et al.
for facilitation. Inhibition was not sensitive to the background.
The role of perceptual structure in exogenous and endogenous
orienting will be discussed along with the effects of grouping and
Gestalt properties on spatial shifts of attention.
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