Faculty of Psychology and Educational Sciences, University of Geneva, Geneva, Switzerland.
Psychophysiology. 2017 Dec;54(12):1826-1838. doi: 10.1111/psyp.12962. Epub 2017 Jul 28.
Search for a shape target is difficult when its shape is similar to the shape of the surrounding nontargets and easy when it is dissimilar. We asked whether interference from a salient but irrelevant color singleton depended on search difficulty as manipulated by target-nontarget similarity. We found that interference was strong in difficult searches, and the occurrence of an electrophysiological index of attentional selectivity (the N2pc component) confirmed that attention was captured by the distractor. In contrast, interference from the distractor was weak with easy searches, and the occurrence of the P component confirmed that saliency signals from the distractor were suppressed. The results suggest that attentional suppression of salient but irrelevant distractors is only possible when search is efficient (i.e., with low target-nontarget similarity), otherwise, attentional capture occurs. Further, we analyzed the Ppc component, a positivity occurring between 100 and 200 ms after stimulus onset contralateral to a salient feature discontinuity. It has been suggested that the Ppc reflects bottom-up saliency signals, but we found the Ppc to occur only when the salient stimulus was unlikely to be selected, as in efficient searches. Thus, attentional requirements modulate the Ppc component.
当目标的形状与其周围的非目标形状相似时，搜索目标会很困难，而当目标形状与非目标形状不同时，搜索目标则会很容易。我们想知道，在目标-非目标相似性被操纵的情况下，一个显著但不相关的颜色单一干扰是否取决于搜索的难度。我们发现，在困难的搜索中，干扰很强，并且注意选择性的电生理指标（N2pc 成分）的出现证实了注意被干扰物所捕获。相比之下，在容易的搜索中，干扰物的干扰很弱，并且 P 成分的出现证实了干扰物的显著信号被抑制。研究结果表明，只有当搜索效率高（即目标-非目标相似度低）时，才能对显著但不相关的干扰物进行注意力抑制，否则，注意力就会被捕获。此外，我们还分析了 Ppc 成分，这是一种在刺激出现后 100 到 200 毫秒之间在与显著特征不连续相对侧出现的正性成分。有人认为 Ppc 反映了自下而上的显著信号，但我们发现只有当显著刺激不太可能被选择时，才会出现 Ppc，例如在高效搜索中。因此，注意力的要求调节了 Ppc 成分。
