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Yiwen Wang, Alejandro Lleras, Simona Buetti; Search for center-surround colored stimuli highlights peripheral vision processing limitations. Journal of Vision 2021;21(9):2136. doi: https://doi.org/10.1167/jov.21.9.2136.
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© ARVO (1962-2015); The Authors (2016-present)
Peripheral vision processes information in parallel, and contributes to efficient visual search performance, with a signature RT function that increases logarithmically with set size. Recent work demonstrated that search efficiency when target and distractors differ along both color and shape can be predicted by search efficiency observed in single-feature search (color-only and shape-only search tasks). Following that logic, we conducted a set of experiments to investigate search efficiency when stimuli are defined as a combination of two colors, in a center-surround arrangement. In Experiment 1, we found that searching for the red-center/green-surround target among the reversed color distractors had larger RTs than searching among same center-color distractors, same surround-color distractors or irrelevant color distractors. Surprisingly, RT functions did not follow either a logarithmic nor a monotonic linear function in none of the distractor conditions. In Experiments 2-3, we decomposed the target and distractors by keeping the center or surround color blank and the results did follow logarithmic functions. These results demonstrate that although observers can process single-color objects in parallel, they struggle searching through two-color objects, indicating either a difficulty maintaining the center-surround target template in memory or a difficulty using peripheral vision to make target-distractor comparisons in two-color stimuli conditions. We ran three additional experiments to investigate this pattern of results. In Experiment 4 , we tested the hypothesis that observers were using a singleton search strategy by instructing them to use that strategy. In Experiment 5, we reminded observers of the search target at the start of each trial. In both cases, we found evidence that participants were not using the target template but rather were relying on the singleton search strategy. However, when we changed the color configuration to two colors one above the other in Experiment 6, we once again found evidence of parallel efficient processing.
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