| A color singleton can involuntarily capture a person's visual attention and interfere with locating a target. However, such attentional capture is modulated by a person's attentional set, that is, a person's expectations and top-down knowledge concerning which perceptual features are relevant and irrelevant to locating the target (C. L. Folk, R. W. Remington, & J. C. Johnston, 1992). Specifically, singletons with relevant features capture attention, but those with irrelevant features do not. Indeed, attentional capture from a color singleton is often absent when no perceptual feature is relevant to target localization and observers must search serially to locate the target. If an attentional set must be maintained in working memory to preclude attentional capture by an irrelevant singleton, it follows that if working memory capacity is overloaded, the attentional set cannot be maintained, and an irrelevant singleton may then capture attention even though it does not capture attention when working memory capacity is not overloaded. Congruent with this logic, I found that when working memory capacity is overloaded, observers could not utilize the attentional set and an irrelevant color singleton captured attention in a stimulus-driven manner. In contrast, when working memory capacity was sufficient for maintaining an attentional set, that same singleton did not capture attention. However, this was the case only when a singleton's identity was response-neutral with respect to the target; when a singleton distractor was response-relevant it captured attention whether working-memory load was high or low. Nonetheless, the results suggest that simply having top-down knowledge as to which features are relevant and irrelevant is insufficient to preclude an irrelevant singleton from capturing attention. Rather, a person must have sufficient working memory capacity for actively maintaining top-down feature information active in working memory for that knowledge to be effective in selecting relevant information for processing while ignoring irrelevant information. |
