To have control over our actions, our interactions with the external world require mechanisms that selectively designate part of the available sensory information. The fact that humans detect and identify visual objects that are not relevant for a task at hand, or that even disturb the processing of a target object, indicates that selective attention does not work perfectly. Previous research has often used the color-word Stroop task to study the way in which control is exerted and under what conditions control fails. In seminal experiments, Stroop (1935) showed participants cards with color words printed in different ink colors and cards with colored patches. When the participants named the colors, they had more difficulty in naming incongruent stimuli (e.g., saying "green" to the word RED in green ink) than in naming neutral stimuli (e.g., saying "green" to the patch of green). The response latencies were longer and more errors were made when the color and the word information did not match than in the neutral condition. This finding that the word input involuntarily interferes with naming the color is very robust and has been repeated numerous times (see MacLeod, 1991, for a review of the Stroop literature). The Stroop effect demonstrates that irrelevant information may influence selective attention mechanisms.In the last 2 decades, variants of the standard Stroop task have been used to study the effects of varied exposure durations of target and distractor on selective attention mechanisms. Can separating object attributes, such as color and shape, in time help us ignore irrelevant aspects of a visual scene? This issue is addressed in the present article. First, we will summarize previous research on temporal segregation of target and distractor and will discuss different explanations for the major findings. Then, we will present three experiments that were designed to assess the relative merits of the different explanations. Finally, in the General Discussion section, we will consider the theoretical implications of our results.In a seminal unpublished study, Neumann (1986) found that when a to-be-named color bar was removed shortly (i.e., 150 msec) after the onset of a color-word Stroop stimulus, the interference effect in naming the color was reduced. This seems counterintuitive: Although only the distractor word remained in the display, responses exhibited less interference from it, as compared with the more standard situation in which both the target and the distractor stayed present until response. Thus, removing the target from the screen helps people ignore irrelevant information.In a series of experiments investigating color-color interference, La Heij, Kaptein, Kalff, and de Lange (1995) found similar, albeit somewhat contrary, results with regard to the reduced interference effect. They used a variation of the flanker task (Eriksen & Eriksen, 1974), in which a target color bar presented at fixation point was enclosed by color bar distractors immediately to the left and right of the target. In the ...
