## 5 Discussion  
The security control operator must search for objects of different shapes. The set of prohibited items includes objects whose size on screen does not exceed 175.1 px, i.e., the maximum error value. Therefore, the operator may look at a prohibited item, but it will not be scored due to an error in the measuring device. The best results can be obtained when the area of the object is larger than the error that can occur. In this case, there are two situations in which a 100% image marking performance will occur (Figure 7a,b). This situation occurs when the operator focuses his or her gaze near the object's center. The further the gaze is away from the center, the more likely it is that the error in the indication of the gaze position will not coincide with the object area (Figure 7c). On the other hand, if the operator concentrates his or her gaze outside the object area, but close to it (Figure 7d) then the system may work in his or her favor. An error in this case may indicate that the operator has identified the correct object. However, the greater the distance of gaze from the object is, the more likely it is the system will adequately judge that the operator has missed the object. The situation strives for a situation in which the system makes a 100% correct assessment for this case (Figure 7e). When the object has a smaller area than the magnitude of the error occurring, cases according to Figure 8 are possible. Note the analogy with Figure 7 in cases (c)-(e). For cases (a) and (b), however, there is an area where the system may misinterpret because the magnitude of the error may occur outside the area of the object. Figure 7: Various scenarios of eye-tracking technology applications where the radius of the object area is larger than the radius of the error. (**a**) The point of gaze focus matches the center point of the object; (**b**) the point of gaze focus is inside the object area but does not match the center point of the object, the area of error is within the boundary of the object area; (**c**) the point of gaze focus is inside the object area but does not match the center point of the object and the area of error is partially within the boundary of the object area; (**d**) the point of gaze focus is outside the object area and the area of error is partially within the boundary of the object area; (**e**) the point of gaze focus is outside the object area and the area of error is outside the boundary of the object area. However, actual prohibited objects on the ICAO list have shapes that are much more complex than circles. If the common part of the error area and the actual area occupied by the object are considered, the probability of the system making the correct decision may be very low. This is shown in Figure 9a, where the scissors have a small part in common with a deviation in the interpretation of the point of gaze likely to occur. However, it is possible to simplify any shape by inscribing it in a figure surrounding its most protruding points (Figure 9b). Such a procedure, however, results in a two-sided effect. The probability of the system's correct decision is increased if the operator looks at the object. However, suppose the operator does not see the object but pays attention to another object in the immediate vicinity (inside the figure in which the object is inscribed). In that case, the system will make an error. The situation will also worsen if the operator does not direct his attention to the center of the forbidden object (Figure 9c). The experiment's results open significant avenues for future research to optimize the technology used to evaluate airport security screening operators. One key area for further analysis is minimizing errors caused by the inaccuracy of eye-tracking technology and  
Figure 8: Various scenarios of eye-tracking technology applications where the radius of the object area is smaller than the radius of the error.