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Abstract:
A singleton can be defined as a unique element that pops out
of a homogeneous display. We reported previously that the effect of
singleton distractors on visual search for an orientation singleton
target varies with distractor type. An orientation distractor
delayed search while distractors dissimilar (color, luminance,
flicker) to the target were relatively ineffective (1). Thus,
singletons do not necessarily capture attention during search for a
singleton target but rather, visual selection is a competitive
process subject to strong top-down selectivity. In the present
study we examined whether abrupt visual onsets, which are thought
to capture attention automatically (2), always override top-down
selectivity. The abrupt onset (50 ms SOA) of a distractor delayed
search for an orientation singleton target, showing that abrupt
onsets can override top-down selectivity for a singleton. Since our
earlier work showed a flickering bar to be an ineffective
distractor, it is probably the appearance of new perceptual objects
rather than visual transients that capture attention (2). However,
an abrupt onset distractor had no effect on a search for a
non-singleton target in a display of randomly oriented bars,
indicating that abrupt onsets do not always capture attention.
Supported in part by a grant from the Emory University Research
Committee-References: 1. Patel & Sathian, Soc. Neurosci. Abstr.
24:659.1, 1998. 2. Egeth & Yantis, Annu. Rev. Psychol. 48:
269-297, 1997.
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