The effect of attention on the phenomenal appearance of objects was investigated in the domains of color (hue), location, line orientation, and spatial frequency. Observers indicated the appearance of a briefly presented above-threshold stimulus by selecting a matching stimulus along a sensory continuum (e.g., color). Attention was manipulated with a dual task that involved letter identification. Attention had little effect in changing the way objects appeared in terms of observers' mean response. However, in each stimulus domain, attention reduced the variability of responses. It is argued that attention should be viewed in terms of reducing uncertainty. Kurt Koffka (1935) suggested that the main question in the study of visual perception is, "Why do things look as they do?" Before answering the question of why the world appears as it does, one needs a description of how the world appears. In the study of visual attention, researchers are at a considerable disadvantage because they have little knowledge of how attention affects the appearance of objects. In the research reported here, we addressed this deficit by examining how attention would affect the appearance of objects. Does attention make objects appear more intense, brighter, longer, or more clear than they would otherwise appear? How does attention affect the perceived color, location, or orientation of objects? Nineteenth-century sensory physiologists and psychologists were concerned with the phenomenology of attention. Investigators, including Mach, Fechner, Wiindt, Titchener, Mu'ller, James, and others, were concerned with the phenomenal quality imparted to objects by attention (for reviews,

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