Institut Mensch in komplexen Systemen
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Publikation How realistic is threat image projection for X-ray baggage screening?(MDPI, 13.03.2022) Riz à Porta, Robin; Sterchi, Yanik; Schwaninger, AdrianAt airports, security officers (screeners) inspect X-ray images of passenger baggage in order to prevent threat items (bombs, guns, knives, etc.) from being brought onto an aircraft. Because threat items rarely occur, many airports use a threat-image-projection (TIP) system, which projects pre-recorded X-ray images of threat items onto some of the X-ray baggage images in order to improve the threat detection of screeners. TIP is regulatorily mandated in many countries and is also used to identify officers with insufficient threat-detection performance. However, TIP images sometimes look unrealistic because of artifacts and unrealistic scenarios, which could reduce the efficacy of TIP. Screeners rated a representative sample of TIP images regarding artifacts identified in a pre-study. We also evaluated whether specific image characteristics affect the occurrence rate of artifacts. 24% of the TIP images were rated to display artifacts and 26% to depict unrealistic scenarios, with 34% showing at least one of the two. With two-thirds of the TIP images having been perceived as realistic, we argue that TIP still serves its purpose, but artifacts and unrealistic scenarios should be reduced. Recommendations on how to improve the efficacy of TIP by considering image characteristics are provided.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Effects of time on task, breaks, and target prevalence on screener performance in an X-ray image inspection task(2019) Buser, Daniela; Sterchi, Yanik; Schwaninger, Adrian; John, MalaCurrently, it is not clear how long security officers can maintain their performance when inspecting X-ray images of passenger bags for prohibited items. New technologies and working environments in airport security screening could profit from longer screening durations, and they might also facilitate performance upkeep. In our study, two groups of security officers conducted a one-hour simulated cabin baggage screening task. One group took 10-minute breaks every 20 minutes; the other worked continuously. Both groups worked under two different target prevalence conditions. Results showed a shift in response tendency that developed at the beginning of the task. Moreover, security officers were able to maintain their visual inspection performance over the course of one hour. There was no difference in performance between the group with breaks and the group without breaks. These results lay the groundwork for further testing longer screening durations in the field.04B - Beitrag KonferenzschriftPublikation Detection measures for visual inspection of X-ray images of passenger baggage(Springer, 2019) Sterchi, Yanik; Hättenschwiler, Nicole; Schwaninger, AdrianIn visual inspection tasks, such as airport security and medical screening, researchers often use the detection measures d' or A' to analyze detection performance independent of response ten-dency. However, recent studies that manipulated the frequency of targets (target prevalence) indicate that da with a slope parameter of 0.6 is more valid for such tasks than d' or A'. We in-vestigated the validity of detection measures (d', A', and da) using two experiments. In the first experiment, 31 security officers completed a simulated X-ray baggage inspection task while re-sponse tendency was manipulated directly through instruction. The participants knew half of the prohibited items used in the study from training, whereas the other half were novel, thereby es-tablishing two levels of task difficulty. The results demonstrated that for both levels, d' and A' de-creased when the criterion became more liberal, whereas da with a slope parameter of 0.6 re-mained constant. Eye-tracking data indicated that manipulating response tendency affected the decision component of the inspection task rather than search errors. In the second experiment, 124 security officers completed another simulated X-ray baggage inspection task. Receiver op-erating characteristic (ROC) curves based on confidence ratings provided further support for da, and the estimated slope parameter was 0.5. Consistent with previous findings, our results imply that d' and A' are not valid measures of detection performance in X-ray image inspection. We recommend always calculating da with a slope parameter of 0.5 in addition to d' to avoid poten-tially wrong conclusions if ROC curves are not available.01A - Beitrag in wissenschaftlicher Zeitschrift