Existing theories of visual search are generally deduced from lab-based studies involving the identification of a target object among similar distractors. The role of the right parietal cortex in visual search is well-established. However, less is known about real-world visual search tasks, such as X-ray screening, which require targets to be disembedded from their background. Research has shown variations in the cognitive abilities required for these tasks and typical lab-based visual search tasks. Thus, the findings of traditional visual search studies do not always transfer into the applied domain. Although brain imaging studies have offered insights into visual search tasks involving disembedding, highlighting an association between the left parietal cortex and disembedding performance, no causal link has yet been established. To this end, we carried out a pilot study (n = 34, between-subjects) administering non-invasive brain stimulation over the posterior parietal cortex (PPC) prior to completing a security X-ray screening task. The findings suggested that anodal left PPC tDCS enhanced novice performance in X-ray screening over that of sham stimulation, in line with brain imaging findings. However, the efficacy of tDCS is under question, with a growing number of failed replications. With this in mind, this study aims to re-test our original hypothesis by examining the effects of left-side parietal stimulation on novice X-ray screener performance and comparing them to those of sham stimulation and of stimulation on a control site (right PPC). As such, this within-subjects study comprised three sessions (2 mA left PPC, 2 mA right PPC, low-intensity sham stimulation left PPC), to investigate effects of anodal tDCS on X-ray screening performance. The pre-registered analysis did not detect any significant differences between left PPC tDCS and sham tDCS or left PPC tDCS and right PPC tDCS on novice performance (d′) in X-ray screening. Further exploratory analyses detected no effects of left PPC tDCS on any other indices of performance in the X-ray security screening task (c, RTs and accuracy), or a disembedding control task (RTs and accuracy). The use of alternative stimulation techniques, with replicable behavioural effects on the parietal lobe (or a multi-technique approach), and well-powered studies with a systematic variation of stimulation parameters, could help to choose between two possible interpretations: that neither left nor right PPC are causally related to either tasks or that tDCS was ineffective. Finally, low-intensity sham stimulation (.016 mA), previously shown to outperform other sham conditions in between-subjects designs, was found to be ineffective for blinding participants in a within-subjects design. Our findings raise concerns for the current lack of optimal control conditions and add to the growing literature highlighting the need for replication in the field.

现有的视觉搜索理论通常是从基于实验室的研究中得出的，这些研究涉及在类似干扰物之间识别目标对象。右顶叶皮层在视觉搜索中的作用是众所周知的。但是，对于现实世界中的视觉搜索任务（例如X射线筛查）知之甚少，这些任务要求将目标从其背景中嵌入。研究表明，这些任务和典型的基于实验室的视觉搜索任务所需的认知能力各不相同。因此，传统视觉搜索研究的发现并不总是转移到应用领域。尽管脑成像研究提供了有关涉及去嵌入的视觉搜索任务的见解，突显了左顶叶皮层与去嵌入性能之间的关联，但尚未建立因果关系。为此，ñ = 34，受试者之间）在完成安全X射线检查任务之前，在顶叶后皮质（PPC）上进行非侵入性脑刺激。研究结果表明，与大脑影像学研究结果相吻合，阳极假性PPC tDCS在X射线筛查中的新手性能比假刺激高。但是，tDCS的有效性受到质疑，复制失败的次数越来越多。考虑到这一点，本研究旨在通过检查左侧壁刺激对新手X射线筛查仪性能的影响并将其与假刺激和对照部位刺激的影响进行比较，从而重新检验我们的原始假设（正确的PPC ）。因此，该受试者内部研究包括三个阶段（左侧2 PmA，右侧2P mA，低强度假刺激左侧PPC），研究阳极tDCS对X射线检查性能的影响。预先注册的分析在X射线筛查中没有发现左PPC tDCS和假tDCS或左PPC tDCS和右PPC tDCS之间在新手表现（d'）上的任何显着差异。进一步的探索性分析未检测到左PPC tDCS对X射线安全检查任务（c，RT和准确性）或解嵌入控制任务（RT和准确性）中任何其他性能指标均无影响。使用对顶叶具有可复制行为影响的替代刺激技术（或多种技术方法）以及功能强大的刺激参数系统变化的研究，可以帮助您在两种可能的解释之间进行选择：既不左也不左正确的PPC与任务有关，或者tDCS无效。最后，发现低强度假刺激（.016 mA）先前表现出优于受试者之间设计中的其他假条件，但被发现对受试者内部设计中的参与者盲目无效。我们的发现引起了人们对当前缺乏最佳控制条件的担忧，并增加了越来越多的文献，强调了在该领域进行复制的必要性。