Investigating training, transfer and viewpoint effects resulting from recurrent CBT of X-Ray image interpretation

Abstract

X-ray screening of passenger bags is an essential task at airport security checkpoints. In this study we investigated how well airport security screeners can detect guns, knives, improvised explosive devices (IEDs) and other threat objects in X-ray images of passenger bags before and after 3 and 6 months of recurrent (about 20 min per week) computer-based training (CBT). Two experiments conducted at different airports gave very similar results. Training with X-ray Tutor (XRT), an individually adaptive CBT, resulted in large performance increases, especially for detecting IEDs. While performance for detecting IEDs was initially substantially lower than for guns, IEDs could be detected as well as guns after several months of training. A large transfer effect was observed as well: Training with XRT helped screeners recognize new threat objects that were similar in shape as the trained objects. Threat recognition was dependent on the rotation of the objects. If depicted from an unusual viewpoint, prohibited items were more difficult to recognize. The results were compared to two conventional (not adaptive) CBT systems. For one system no training and transfer effects were observed whereas small training and transfer effects were found for the other conventional CBT system.