Abstract
Goal. Feature-based attention can enhance perception to an attended color. However, it is less clear how attending to a color modulates processing of nearby colors. The feature-similarity gain model predicts a graded level of attentional enhancement centered on the attended color. However, a center-surround mechanism claims inhibition of colors nearby the attended one (Stormer & Alvarez, 2014). Here, we investigate how attentional modulation varies systematically as a function of the difference between the stimulus color and the attended color. Methods. Subjects were sequentially presented with two intervals, with each interval consisting of a patch of static colored dots. In one patch all dots had random colors, while in the other patch one color was overrepresented (the target). Subjects performed a 2IFC task reporting the interval that contained the target. The amount of overrepresentation was determined by interleaved staircases for each target color and each subject in a thresholding session at the start of the experiment. In the cueing condition, a fixed-color cue appeared briefly at the beginning of each trial. The target matched this color on 50% of trials. In the remaining trials, the target was ±15°, ±30°, ±45° or ±60° away from the cued color (6.25% each) on a color wheel (CIE L*a*b space). In separate blocks of neutral trials, there were no cues. The cueing effect was the difference between the neutral and cued conditions for a given color. Results. For most subjects, we found a significant enhancement for the cued target color and, more importantly, a general trend for inhibition at its immediate neighbors (±15°). Once outside this inhibitory zone, there was a rebound of cueing effect. Thus, our data are consistent with a surround-suppression effect in feature-based attention. We also found evidence for an interaction between attentional modulation and category boundaries in the color space.
Meeting abstract presented at VSS 2017