2019-09-20, Merks, Sarah, Hügli, David, Hättenschwiler, Nicole, Schwaninger, Adrian

2019-09-10, Zeballos, Melina, Merks, Sarah, Hättenschwiler, Nicole, Schwaninger, Adrian

With the transition from 2D to 3D imaging technology for security screening of passenger bags, the question arises whether airport security screeners need the same visual-cognitive abilities to successfully inspecting these images. This study investigated the relationship between visual-cognitive abilities and the visual inspection performance of screeners. 42 screeners conducted a visual-cognitive test battery (VCTB) and a simulated hold baggage screening task using 2D or 3D imaging technology. The VCTB included test scales measuring abilities underlying visual processing, processing speed and fluid intelligence. Results showed that only few aspects of processing speed and visual processing correlated significantly with performance using 2D imaging. Performance of screeners that inspected 3D images showed even less significant correlations. These results indicate that with the expected change from 2D to 3D imaging, visual-cognitive requirements of airport security screeners might change. Further studies need to elucidate what visual-cognitive skills future 3D screeners need.

2019, Sterchi, Yanik, Hättenschwiler, Nicole, Schwaninger, Adrian

In 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.

2019, Hättenschwiler, Nicole, Merks, Sarah, Sterchi, Yanik, Schwaninger, Adrian

The act of looking for targets amongst an array of distractors is a cognitive task that has been studied extensively over many decades and has many real-world applications. Research shows that specific visual-cognitive abilities are needed to efficiently and effectively locate a target among distractors. It is, however, not always clear whether the results from traditional, simplified visual search tasks conducted by students will extrapolate to an applied inspection tasks in which professionals search for targets that are more complex, ambiguous, and less salient. More concretely, there are several potential challenges when interpreting traditional visual search results in terms of their implications for the X-ray image inspection task. In this study, we tested whether a theoretical intelligence model with known facets of visual-cognitive abilities (visual processing Gv, short-term memory Gsm, and processing speed Gs) can predict performance in both a traditional visual search task and an X-ray image inspection task in both students and professionals. Results showed that visual search ability as measured with a traditional visual search task is not comparable to an applied X-ray image inspection task. Even though both tasks require aspects of the same visual-cognitive abilities, the overlap between the tasks was small. We concluded that different aspects of visual-cognitive abilities predict performance on the measured tasks. Furthermore, although our tested populations were comparable in terms of performance predictors based on visual-cognitive abilities, professionals outperformed students on an applied X-ray image inspection task. Hence, inferences from our research questions have to be treated with caution, because the comparability of the two populations depends on the task.

2019-09-11, Isenschmid, Myrta, Hättenschwiler, Nicole, Merks, Sarah, Schwaninger, Adrian

The screening of hold baggage at airports is currently changing from 2D to 3D imaging. In this context, we compared visual inspection performance of screeners using 2D imaging versus 3D imaging versus 3D imaging following a specific on-screen alarm resolution protocol (OSARP). In a simulated hold baggage screening task, professional screeners had to decide whether X-ray images contained an improvised explosive device or not. Results showed that there was no difference in detection performance (d') between 2D and 3D imaging. Visual inspection with 3D imaging following an OSARP resulted in higher detection performance compared to 2D and 3D imaging, but also in a more neutral response bias and longer reaction times. In conclusion, screeners currently working with 2D technology do not need extensive and specific training to achieve comparable detection performance with 3D imaging. However, the application of an OSARP has the potential to further increase screeners’ detection performance.

2019-09-10, Merks, Sarah, Hättenschwiler, Nicole, Sterchi, Yanik, Schwaninger, Adrian

Visual search has been studied extensively over decades and has many real-world applications. Research shows that specific visual-cognitive abilities are needed to efficiently and effectively locate a target among distractors. It is, however, not clear whether the results from traditional, simplified visual search tasks conducted by students will extrapolate to an applied inspection task, i.e. X-ray image inspection in airport security. In this study, we tested whether the same visual-cognitive abilities can predict performance in both a traditional visual search task and an X-ray image inspection task in students and professionals. Results showed that even though both tasks require aspects of the same visual-cognitive abilities, the overlap between the tasks was small. Furthermore, although our tested populations were comparable in terms of required visual-cognitive abilities, professionals outperformed students in the X-ray image inspection task. This suggests that visual inspection is not solely predictable by visual-cognitive abilities.

2019, Hättenschwiler, Nicole, Merks, Sarah, Isenschmid, Myrta, Schwaninger, Adrian, Jäger, Matthias

2D Röntgensysteme mit multi-view Technologie werden an Flughäfen zur Erkennung von Sprengstoff bei registriertem Gepäck verwendet. Neuere Röntgensysteme basieren auf Computer Tomographie (CT), wobei Gepäckstücke als 3D-rotierbare Bilder dargestellt werden. Es steht zur Diskussion, ob Screener mit 2D Erfahrung spezifisches Training benötigen, bevor sie mit 3D arbeiten können. Zur Unterstützung der Alarmauflösung bei 3D gibt es zusätzlich On-screen Alarm Resolution Protokolle (OSARP), dessen Effektivität bisher noch nicht untersucht wurde. Um diesen Fragen nachzugehen, wurden in einem Experiment drei Bedingungen verglichen. In der ersten Bedingung bearbeiteten Screener eine Inspektionsaufgabe mit 2D multi-view Technologie (2D), in der zweiten Bedingung mit 3D CT Technologie (3D) und in der dritten Bedingung mit 3D und einem vorher durchgeführten Training zu OSARP. Die Ergebnisse zeigen, dass es keine Unterschiede bezüglich der Erkennungsleistung (d’) zwischen 2D und 3D gibt. Unter der Befolgung eines OSARP erreichten die Screener eine höhere Erkennungsleistung als bei 2D und 3D. Die Reaktionszeiten waren bei den 3D Bedingungen länger als bei 2D. Die Resultate zeigen, dass Screener, welche momentan mit 2D multi-view Technologie arbeiten, kein spezifisches Training brauchen, um eine ähnliche Erkennungsleistung mit 3D Technologie zu erreichen. Die Nutzung eines OSARP könnte die Erkennungsleistung zusätzlich noch verbessern.

2019-09-10, Sterchi, Yanik, Hättenschwiler, Nicole, Schwaninger, Adrian

Researchers often use the detection measures d' and A' to analyze detection performance in X-ray image inspection task. We investigated whether detection measures (d', A', and da) are truly independent of response tendency. In a first experiment, response tendency was manipulated directly through instruction and resulted in a decrease of d' and A', whereas da with a slope parameter of 0.6 remained constant. Eye-tracking data indicated that manipulating response tendency affected the decision component of the inspection task rather than search errors. Receiver operating characteristic (ROC) curves based on confidence ratings from a second experiment also supported da. Consistent with previous findings, our results imply that d' and A' are not always valid measures of detection performance in X-ray image inspection. We recommend calculating da with a slope parameter of 0.5 in addition to d' to avoid wrong conclusions if ROC curves are not available.

2019, Hättenschwiler, Nicole, Mendes, Marcia, Schwaninger, Adrian

Objective: This study compared the visual inspection performance of airport security officers (screeners) when screening hold baggage with state-of-the-art 3D versus older 2D imaging. Background: 3D imaging based on computer tomography features better automated detection of explosives and higher baggage throughput than older 2D X-ray imaging technology. Nonetheless, some countries and airports hesitate to implement 3D systems due to their lower image quality and the concern that screeners will need extensive and specific training before they can be allowed to work with 3D imaging. Method: Screeners working with 2D imaging (2D screeners) and screeners working with 3D imaging (3D screeners) conducted a simulated hold baggage screening task with both types of imaging. Differences in image quality of the imaging systems were assessed with the standard procedure for 2D imaging. Results: Despite lower image quality, screeners’ detection performance with 3D imaging was similar to that with 2D imaging. 3D screeners revealed higher detection performance with both types of imaging than 2D screeners. Conclusion: Features of 3D imaging systems (3D image rotation and slicing) seem to compensate for lower image quality. Visual inspection competency acquired with one type of imaging seems to transfer to visual inspection with the other type of imaging. Application: Replacing older 2D with newer 3D imaging systems can be recommended. 2D screeners do not need extensive and specific training to achieve comparable detection performance with 3D imaging. Current image quality standards for 2D imaging need revision before they can be applied to 3D imaging.

2019, Merks, Sarah, Hättenschwiler, Nicole, Zeballos, Melina, Schwaninger, Adrian, Jäger, Matthias

Für die Sicherheitskontrolle von registriertem Gepäck ver-wenden Flughäfen 2D multi-view Röntgentechnologie. Neue Technologien basieren auf 3D CT und ermöglichen eine 360 Grad Ansicht des Gepäckstücks. Für den Wechsel von 2D auf 3D Screening stellt sich die Frage, ob Screener für diese Technologien dieselben visuell-kognitiven Fähigkeiten benötigen. Deshalb untersuchte diese Studie den Zusammenhang zwischen visuell-kognitiven Fähigkeiten und der Inspektionsleistung. Die Screener absolvierten eine visuell-kognitive Testbatterie (VCTB) bestehend aus 10 standardisierten Testskalen und eine simulierte 2D sowie 3D Screening Aufgabe. Die Resultate zeigen, dass Aspekte von Informationsverarbeitungsgeschwindigkeit und von visueller Verarbeitung signifikant mit der Inspektionsleistung in der 2D Aufgabe korrelieren. Mit der 3D Aufgabe hin-gegen korrelierte nur mit ein paar wenigen Skalen der VCTB. Diese Resultate weisen darauf hin, dass sich die visuell-kognitiven Anforderungen an Screener mit der Einführung von 3D CT Technologie ändern könnten.