Abstract
Splitting attention between targets of different colors is not costly by itself. As we found previously, however, monitoring a target of a particular color makes one more vulnerable to interference by distracters that share the target color. Participants monitored the changing spatial frequencies of two targets of either the same (e.g., red and red) or different colors (e.g., red and green). The changing stimuli disappeared without warning and participants reported the final spatial frequency of one of the targets. In the different-colors condition, a large cost occurs if a green distracter is superposed on the red target in the first location and a red distracter is superposed on the green target in the second location. This likely reflects a difficulty with attending to a color in one location while ignoring it in another. Here we focus on a subsidiary finding regarding perceptual lags. Participants reported spatial frequency values from the past rather than the correct final value, and such lags were greater in the different-colors condition. This "perceptual lag" cost was found when the two stimuli were horizontally arrayed but not, curiously, when they were vertically arrayed. Arrangement was confounded however with processing by separate brain hemispheres (opposite hemifields). In our new study, we unconfounded arrangement and presentation in separate hemifields with a diagonal condition- targets were not horizontally arrayed but were still presented to different hemifields. No significant different-colors lag cost was found in this diagonal arrangement (5 ms) or in the vertical arrangement (86 ms), but the cost (167 ms) was significant in the horizontal arrangement, as in previous experiments. Horizontal arrangement apparently has a special effect apart from the targets being processed by different hemispheres. To speculate, this may reflect sensitivity to bilateral symmetry and its violation when the target colors are different.
Meeting abstract presented at VSS 2012