Stimulus competition modulates the joint effects of spatial and feature-based attention on visual sensitivity

摘要

Goal: Selectively monitoring a location in the peripheral visual field improves perceptual judgements and enhances neural responses to stimuli at that location. In addition, attending to a particular feature value, such as a specific color, improves processing of items with that feature across the visual field. We investigated whether and how spatial and feature-based attention interact to modulate visual sensitivity in a discrimination task. Methods: Observers monitored overlapping groups of dots for a subtle change in color saturation, which they had to localize as being in the upper or lower hemifield. At the start of each trial, a pre-cue indicated the most likely side (left or right), color (red or green), or both side and color of the target saturation change. The location cue and the color cue could each be valid, neutral, or invalid, and we measured sensitivity (d') for every combination. In Experiment 1, only one patch of dots changed in saturation. In Experiment 2, there were three other saturation changes (distractors) simultaneous with the target change. A post-cue indicated which dots to judge. Results: For both cue types, d' was higher in valid than invalid trials. When only a single saturation change occurred, the location and color cueing effects were statistically independent and approximately additive. However, when competing saturation changes occurred simultaneously with the target saturation change, the location and color cueing effects interacted. The effect (i.e. valid d' a?? invalid d') of each type of cue was strongest when the other type of cue was valid. Moreover, spatial attention was only effective in modulating sensitivity for attended colors. Conclusion: In light of these findings and previous physiological studies, we conclude that spatial and feature-based attention can operate independently. However, their joint consequences for perception depend on the presence of competing visual information.