Michel, Stefan

Michel, Stefan


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  • Publikation
    Expertise, automation and trust in X-ray screening of cabin baggage
    (Frontiers, 2019) Chavaillaz, Alain; Schwaninger, Adrian; Michel, Stefan; Sauer, Jürgen [in: Frontiers in Psychology]
    X-ray screening of passenger baggage is a key component in aviation security. The current study investigated how experts and novices performed in an X-ray baggage screening task while being assisted by an adaptable diagnostic aid. Furthermore, it examined how both groups operated and trusted this automated system. 30 experts (certified screeners) and 31 novices (students) had to indicate whether a target item (either a knife or a gun) was present in a series of X-ray images of cabin baggage. Half of the participants could choose between three different support levels of the diagnostic aid (DA): (1) no support, (2) a cue indicating the presence of a potential target without locating it, or (3) a cue indicating the presence of a potential target by surrounding it with a red frame. As expected, experts achieved higher detection performance (d’), were more self-confident and felt more competent in achieving the task than novices. Fur-thermore, experts experienced less time pressure and fatigue. Although both groups used the DA in a comparable way (in terms of support level used and frequency of level switches), re-sults showed a performance increase for novices working with the DA compared to novices without support. This benefit of DA was not observed for experts. Interestingly, despite no differ-ence in perceived trust ratings, experts were more compliant (i.e., following DA recommenda-tions when it indicated the presence of a target) and reliant (i.e., following DA recommendations when it indicated the absence of a target) than novices. Altogether, the results of the present study suggested that novices benefited more from a DA than experts. Furthermore, compliance and reliance on DA seemed to depend on expertise with the task. Since experts should be bet-ter at assessing the reliability of the DA than novices, they may have used the DA as ‘back-up’ to confirm their decisions based on expertise (confirmatory function), while novices may have used it as a guide to base their decisions on (support function). Finally, trust towards a DA was associated with the degree to which participants found the DA useful.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Work design for airport security officers: Effects of rest break schedules and adaptable automation
    (Elsevier, 2019) Chavaillaz, Alain; Schwaninger, Adrian; Michel, Stefan; Sauer, Jürgen [in: Applied Ergonomics]
    This study investigated whether there is empirical support for the current EU regulation mandat-ing breaks of at least 10 min after each period of 20 min continuously reviewing X-ray images in airport security screening. As a second goal, it examined whether providing more autonomy to airport security officers (in the form of spontaneous rest breaks and adaptable automation) would improve their performance and subjective state. Seventytwo student participants had to indicate the presence (or absence) of a threat item (either a gun or a knife) in a series of grey-scaled X-ray images of cabin baggage. Three work-rest schedules were examined: spontane-ous breaks (i.e. participants could take breaks at any time), two 5-min breaks and two 10-min breaks during a 1-h testing session. Furthermore, half of the participants were assisted in their task by an adaptable support system offering three levels of automation: (1) no support, (2) cues indicating the presence of a potential threat item, and (3) cues indicating the exact location of a potential threat item. Results showed no performance differences between break regimes, which suggests that there may be viable alternatives to the current EU regulations. It also emerged that providing participants with adaptable automation did not lead to better detection performance but resulted in a less positive response bias than participants without automatic support. Implications for current aviation security regulations are discussed.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Increasing X-ray image interpretation competency of cargo security screeners
    (Elsevier, 14.08.2014) Michel, Stefan; Mendes, Marcia; De Ruiter, J.C; Koomen, Ger; Schwaninger, Adrian [in: International Journal of Industrial Ergonomics]
    01A - Beitrag in wissenschaftlicher Zeitschrift