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People have difficulty performing two tasks at once. For example, maintaining items in working memory (WM) makes people more distractible. However, different types of WM load may have different effects on attentional selection depending on whether WM load overlaps with mechanisms involved in target or distractor processing. Three experiments examined the effect of concurrent WM load on Stroop tasks, a widely used measure of executive control and inhibition. Stroop interference increased when the type of WM load overlapped with the type of information required for the target task (experiment 1). In striking contrast, Stroop interference decreased when the type of WM load overlapped with distractor processing (experiment 2). Experiment 3 replicated these results in a different Stroop task. Thus, concurrent WM load does not always impair executive control; performance depends on how contents of WM and task-relevant information overlap. The results highlight how dissociable components of WM interact with perception and executive control.attention ͉ executive control ͉ Stroop interference ͉ cognitive load I n the face of distracting information, attentional mechanisms help to prioritize and select information that is most relevant for current behavioral goals. However, selection is not perfect. Failure to inhibit unnecessary information (i.e., distractors) causes people to slow down and make mistakes. The Stroop interference effect is one of the most straightforward examples in which uninhibited distractor processing interferes with target processing. People are significantly slower to name the ink color of a colored word when the meaning of the colored word is incongruent with the ink color of the word (e.g., ''red'' in blue ink) as opposed to when it is congruent (1). Stroop and other researchers (2-4) explained this interference with the automaticity hypothesis: Word reading is more automatic than color naming. According to this account, the more arduous, attentiondemanding process of color naming is hampered by the more automatic process of word reading (5). However, contrary to predictions from the word automaticity account, Stroop interference can be observed from color distractors in revised versions of the task (5, 6). Thus, a more general explanation of the Stroop effect simply focuses on the inability to ignore distractor information, which may vary in salience depending on the task. Stroop interference occurs whenever observers fail to inhibit distractor information that is incongruent with the target task and response.An important goal of attention research is to understand the conditions that promote selection and reduce distractor interference. Given such robust interference in the Stroop task, are there manipulations to reduce interference? Stroop interference should be reduced if people's attention can be diverted away from the conflicting information. Indeed, an innovative study by Kahneman and Chajczyk (7) successfully reduced the Stroop effect by presenting additional distractors in the display, wh...

In two experiments using spatial probes, we measured the temporal and spatial interactions between top-down control of attention and bottom-up interference from a salient distractor in visual search. The subjects searched for a square among circles, ignoring color. Probe response times showed that a color singleton distractor could draw attention to its location in the early stage of visual processing (before a 100-msec stimulus onset asynchrony [SOA]), but only when the color singleton distractor was located far from the target. Apparently the bottom-up activation of the singleton distractor's location is affected early on by local interactions with nearby stimulus locations. Moreover, probe results showed that a singleton distractor did not receive attention after extended practice. These results suggest that top-down control of attention is possible at an early stage of visual processing. In the long-SOA condition (150-msec SOA), spatial attention selected the target location over distractor locations, and this tendency occurred with or without extended practice.

There has been a controversy on whether working memory can guide attentional selection. Some researchers have reported that the contents of working memory guide attention automatically in visual search (D. Soto, D. Heinke, G. W. Humphreys, & M. J. Blanco, 2005). On the other hand, G.F. Woodman and S. J. Luck (2007) reported that they could not find any evidence of attentional capture by working memory. In the present study, we tried to find an integrative explanation for the different sets of results. We report evidence for attentional capture by working memory, but this effect was eliminated when search was perceptually demanding or the onset of the search was delayed long enough for cognitive control of search to be implemented under particular conditions. We suggest that perceptual difficulty and the time course of cognitive control as important factors that determine when information in working memory influences attention.