To successfully interact with objects in complex and crowded environments, we often perform visual search to detect or identify a relevant target (or targets) among distractors. Previous studies have reported a redundancy gain when two targets instead of one are presented in a simple target detection task. However, research is scant about the role of multiple targets in target discrimination tasks, especially in the context of visual search. Here, we address this question and investigate its underlying mechanisms in a pop-out search paradigm. In Experiment 1, we directly compared visual search performance for one or two targets for detection or discrimination tasks. We found that two targets led to a redundancy gain for detection, whereas it led to a redundancy cost for discrimination. To understand the basis for the redundancy cost observed in discrimination tasks for multiple targets, we further investigated the role of perceptual grouping (Experiment 2) and stimulus–response feature compatibility (Experiment 3). We determined that the strength of perceptual grouping among homogenous distractors was attenuated when two targets were present compared with one. We also found that response compatibility between two targets contributed more to the redundancy cost compared with perceptual compatibility. Taken together, our results show how pop-out search involving two targets is modulated by the level of feature processing, perceptual grouping, and compatibility of perceptual and response features.

为了在复杂和拥挤的环境中成功地与对象交互，我们经常执行视觉搜索来检测或识别干扰项中的相关目标（或多个目标）。以前的研究报告了在简单的目标检测任务中出现两个目标而不是一个目标时的冗余增益。然而，关于多目标在目标识别任务中的作用的研究很少，尤其是在视觉搜索的背景下。在这里，我们解决了这个问题，并在弹出式搜索范式中研究了它的潜在机制。在实验 1 中，我们直接比较了用于检测或识别任务的一两个目标的视觉搜索性能。我们发现两个目标导致检测的冗余增益，而它导致冗余成本为歧视。为了了解在针对多个目标的判别任务中观察到的冗余成本的基础，我们进一步研究了感知分组（实验 2）和刺激-响应特征兼容性（实验 3）的作用。我们确定，当两个目标与一个目标相比时，同质干扰物之间的感知分组强度会减弱。我们还发现，与感知兼容性相比，两个目标之间的响应兼容性对冗余成本的贡献更大。总之，我们的结果显示了涉及两个目标的弹出搜索如何受到特征处理水平、感知分组以及感知和响应特征的兼容性的调节。