@article{ref1,
title="Task-demands can immediately reverse the effects of sensory-driven saliency in complex visual stimuli",
journal="Journal of vision",
year="2008",
author="Einhäuser, Wolfgang and Rutishauser, Ueli and Koch, Christof",
volume="8",
number="2",
pages="2.1-19",
abstract="In natural vision both stimulus features and task-demands affect an observer's attention. However, the relationship between sensory-driven (&quot;bottom-up&quot;) and task-dependent (&quot;top-down&quot;) factors remains controversial: Can task-demands counteract strong sensory signals fully, quickly, and irrespective of bottom-up features? To measure attention under naturalistic conditions, we recorded eye-movements in human observers, while they viewed photographs of outdoor scenes. In the first experiment, smooth modulations of contrast biased the stimuli's sensory-driven saliency towards one side. In free-viewing, observers' eye-positions were immediately biased toward the high-contrast, i.e., high-saliency, side. However, this sensory-driven bias disappeared entirely when observers searched for a bull's-eye target embedded with equal probability to either side of the stimulus. When the target always occurred in the low-contrast side, observers' eye-positions were immediately biased towards this low-saliency side, i.e., the sensory-driven bias reversed. Hence, task-demands do not only override sensory-driven saliency but also actively countermand it. In a second experiment, a 5-Hz flicker replaced the contrast gradient. Whereas the bias was less persistent in free viewing, the overriding and reversal took longer to deploy. Hence, insufficient sensory-driven saliency cannot account for the bias reversal. In a third experiment, subjects searched for a spot of locally increased contrast (&quot;oddity&quot;) instead of the bull's-eye (&quot;template&quot;). In contrast to the other conditions, a slight sensory-driven free-viewing bias prevails in this condition. In a fourth experiment, we demonstrate that at known locations template targets are detected faster than oddity targets, suggesting that the former induce a stronger top-down drive when used as search targets. Taken together, task-demands can override sensory-driven saliency in complex visual stimuli almost immediately, and the extent of overriding depends on the search target and the overridden feature, but not on the latter's free-viewing saliency.<p /><p>Language: en</p>",
language="en",
issn="1534-7362",
doi="10.1167/8.2.2",
url="http://dx.doi.org/10.1167/8.2.2"
}