Department of Psychology, University of Southampton, United Kingdom.
J Exp Psychol Appl. 2012 Dec;18(4):404-18. doi: 10.1037/a0031032.
Searching simultaneously for metal threats (guns and knives) and improvised explosive devices (IEDs) in X-ray images is less effective than 2 independent single-target searches, 1 for metal threats and 1 for IEDs. The goals of this study were to (a) replicate this dual-target cost for categorical targets and to determine whether the cost remains when X-ray images overlap, (b) determine the role of attentional guidance in this dual-target cost by measuring eye movements, and (c) determine the effect of practice on guidance. Untrained participants conducted 5,376 trials of visual search of X-ray images, each specializing in single-target search for metal threats, single-target search for IEDs, or dual-target search for both. In dual-target search, only 1 target (metal threat or IED) at most appeared on any 1 trial. Eye movements, response time, and accuracy were compared across single-target and dual-target searches. Results showed a dual-target cost in response time, accuracy, and guidance, with fewer fixations to target-color objects and disproportionately more to non-target-color objects, compared with single-target search. Such reduction in guidance explains why targets are missed in dual-target search, which was particularly noticeable when objects overlapped. After extensive practice, accuracy, response time, and guidance remained better in single-target search than in dual-target search. The results indicate that, when 2 different target representations are required for search, both representations cannot be maintained as accurately as in separate single-target searches. They suggest that baggage X-ray security screeners should specialize in one type of threat, or be trained to conduct 2 independent searches, 1 for each threat item.
在 X 光图像中同时搜索金属威胁（枪支和刀具）和简易爆炸装置（IEDs）的效果不如 2 次独立的单一目标搜索，1 次用于搜索金属威胁，1 次用于搜索 IEDs。本研究的目的是：（a）复制这种针对分类目标的双重目标成本，并确定当 X 光图像重叠时成本是否仍然存在；（b）通过测量眼动来确定注意力引导在这种双重目标成本中的作用；（c）确定实践对引导的影响。未经训练的参与者进行了 5376 次 X 光图像视觉搜索试验，每次专门针对金属威胁的单一目标搜索、IED 的单一目标搜索或两者的双重目标搜索。在双重目标搜索中，任何 1 次试验中最多只有 1 个目标（金属威胁或 IED）出现。比较了单一目标和双重目标搜索中的眼动、反应时间和准确性。结果显示，与单一目标搜索相比，反应时间、准确性和引导都存在双重目标成本，目标颜色物体的注视次数减少，而非目标颜色物体的注视次数不成比例地增加。这种引导减少解释了为什么在双重目标搜索中会错过目标，当物体重叠时，这种情况尤其明显。经过大量的练习，准确性、反应时间和引导在单一目标搜索中仍然优于双重目标搜索。结果表明，当搜索需要两种不同的目标表示时，这两种表示都不能像在单独的单一目标搜索中那样准确地保持。这表明行李 X 光安检人员应该专门针对一种威胁，或者接受培训进行 2 次独立的搜索，每次搜索针对一种威胁物品。
