... Stimuli used for viewer identification include viewing artificial stimuli [5,20,6,19,8,35,36,33,30], text documents [5,17,30], movies [22] or images [5,8]. Most approaches are designed to identify viewers on a specific stimulus, for example by applying graph matching techniques to the scanpaths produced on a specific face image [29], or even by including a secondary identification task such as entering a PIN or password with the eye gaze [25,23,9,10,34,7]. Approaches that can be applied to novel stimuli at test time extract different kinds of fixational and saccadic features, such as fixation durations [32,14] or saccade amplitudes [14,29,19,30], velocities [5,32,6,29,8,19,11,30] and accelerations [29,8,11,30], and either aggregate these over the whole scanpath [32,17,22,8,14], or compute the similarity of scanpaths by applying statistical tests to the distributions of the extracted features [16,30]. ...