Feature-based attention across the visual field.

摘要

In order to prioritize the perception of behaviorally relevant stimuli, observers can increase their sensitivity to particular visual feature values (such as colors, orientations, or motion directions). This top-down modulation of visual sensitivity is called feature-based attention. Here I report a series of psychophysical experiments that investigate how feature-based attention influences sensitivity across the visual field and interacts with spatial attention. First, I describe a behavioral correlate of a phenomenon first reported in physiology: feature-based attention spreads automatically across hemifields to locations unrelated to the primary task at hand. In a following study I examined more specifically how feature-based attention interacts with covert spatial attention. The two systems enhance visual signals in an independent and roughly additive fashion. However, when there is competing information in the display, the two cueing effects interact, such that the benefit for attended features is greater at attended than unattended locations, and the effects of spatial attention are stronger for attended than unattended features.;I also explored how feature-based attention interacts with the obligatory enhancement of sensitivity at the target of an impending eye movement. This interaction is flexibly contingent on events in the previous trial. A saccade target's visual features are automatically enhanced across the visual field just before the eye movement begins, but only if recent task-relevant stimuli had been similar to the saccade targets in previous trials. Finally, in a fourth study, I found that objects with salient colors can automatically and rapidly draw spatial attention to their locations, but to a smaller extent than the onsets of single objects alone.;I conclude that spatial and feature-based attention are dissociable systems that infiltrate several stages of visual processing. In some of those stages, however, the two types of attention interact and potentiate each other. These findings narrow the gap between our knowledge of neurophysiology and actual perception, and establish how basic visual mechanisms adapt to the observer's goals. Understanding the processes of attentional selection like these helps explain the incredible visual capacities we rely on in complex environments, as well as our perceptual limitations.