The role of recurrent CBT for increasing aviation security screeners’ visual knowledge and abilities needed in x-ray screening

X-ray screeners have to know which items are prohibited and what they look like in x-ray images of passenger bags (knowledge-based factors). In addition, effective x-ray screening requires the abilities to cope with bag complexity, superposition by other objects, and rotation of objects (image-based factors). Knowledge-based factors are expected to be highly dependent on training whereas image-based factors are related to visual-cognitive abilities and aptitudes (Schwaninger, Hardmeier, & Hofer, 2005). To test to what extend these two factors are influenced by training, 334 screeners took two x-ray screening tests before and after two years of recurrent computer-based training (CBT). The Prohibited Items Test (PIT) measures rather knowledge-based factors, the X-Ray Object Recognition Test (X-Ray ORT) image-based factors. The results showed indeed a much better detection performance in the PIT after two years of training. Thus, CBT can increase the knowledge of prohibited items and what they look like in x-ray images of passenger bags substantially. The increase in detection performance in the X-Ray ORT was much smaller. This indicates that image-based factors are indeed related to visual-cognitive abilities and aptitudes that can be increased by CBT less effectively. The implications for selection and training of x-ray screeners are discussed. Introduction Airport security has become very important in recent years. Since airports are confronted with new threat dimensions and a constantly increasing passenger flow, reliable and efficient detection of different threat items in x-ray images is an essential airport security task. During high passenger flow, screeners have only a few seconds to decide whether a bag is OK or whether it has to be hand-searched. Schwaninger, Hardmeier, and Hofer (2005) could show that detecting threat items in passenger bags includes both, knowledge-based and image-based factors. That is, a screener has to know which items are prohibited and what they look like in x-ray images of passenger bags (knowledge-based factors). There are many threat items that look quite different in reality than in an x-ray image, which makes them difficult to recognize without training (Schwaninger, 2005b). Another difficulty results from the fact that some threat items look quite similar to harmless objects. Again other threat items like improvised explosive devices (IEDs) are normally not seen at checkpoints and without specific training they are therefore rather difficult to recognize. These knowledge-based factors are expected to be highly dependent on training since results from object recognition studies show that one can only recognize shapes if they are similar to the ones encountered before and stored in visual memory (for an overview see Schwaninger, 2005a). However, the interpretation of x-ray images is much more complex and is also dependent on imagebased factors such as bag complexity, superposition and rotation of the target object itself. If a bag is close-packed it is more difficult to detect a threat item within a short time because other objects can distract attention. Furthermore, the threat item can be superimposed by other objects in the bag, which can hamper detection performance as well. Moreover, if a threat item is shown in a rotated view it becomes harder to recognize it. A previous study from Schwaninger et al. (2005) showed large individual differences for novices and screeners regarding how well they can cope with such image-based factors.