Improving the performance of airport luggage inspection by providing cognitive and perceptual supports to screeners

Recently concern about aviation security has focused on the work of airport security screeners who detect threat items in passengers' luggage. An effective method of training and screening is required for improving screeners' detection abilities and performance to cope with the unreliable human performance of screening. The overall aim of this thesis is to understand and define the potential visual and cognitive factors in the task of inspecting airport passengers' X-ray luggage images, examine usability of perceptual feedback in this demanding task and develop a new method of salient regions which assist screeners to detect targets. The result of this work would obtain knowledge and skills of X-ray luggage images examination, provide insight into the design of training system and develop a method to significantly enhance screeners' detection ability. A questionnaire was developed for screeners to extract the expertise of the screening task and investigate the effect of image features on visual attention. A series of experiments were designed to understand the screening task and explore how knowledge and skills are developed with practice. Results indicated that training under time stressed conditions is recommended for ensuring adequate high detection ability in real life situation as screeners have to balance accuracy and speed in time pressure. The advantages of screeners are better detection ability and search skills which were gained by experience of the search task. Hit rate of naive people was improved with the perceptual exposure of images of threat items. However, scanning did not become efficient. It has demonstrated that detection performance and search skills are improved by the practice of frequency exposure targets in the search task and such ability partly transfer to novel targets. Learning in visual search of threat items is stimuli specific such that familiarity with stimulus and task is the source of performance enhancement. Threat items should be updated constantly and massive amount of X-ray threat objects should be employed for airport security screeners training so as to enlarge object knowledge and enhance recognition ability. Perceptual feedback of circling areas with dwell duration longer than 1000ms does not Significantly improve observers' detection ability in the airport screening task. Features of bags and threat items influence initial attention and attention allocation in the search process. Salient regions, based on the pure stimulus properties, not only contain most of targets in X-ray images but also improve observers' detection performance of high hit rate by forcing observers to scrutinize these areas carefully.