Using mutual distance plot and warped time distance chart to compare scan-paths of multiple observers

The aim of the research is the introduction of new techniques that enable a visual comparison of scan-paths. Every eye tracking experiment produces many scan-paths, and one of the main challenges of eye tracking analysis is how two compare these scan-paths. A classic solution is to extract easily measurable features such as fixation durations or saccade lengths. There are also many more sophisticated techniques that compare two scan-paths using only spatial or both spatial and temporal information. These techniques typically return a value (or several values) that may be used as scan-path similarity/distance measure. However, there is still a lack of widely adopted methods that offer not only the measure but enable a visual comparison of scan-paths. The paper introduces two possible options: the Mutual Distance Plot for two scan-paths and the Warped Time Distance chart for the comparison of the theoretically unlimited number of scan-paths. It is shown that these visualizations may reveal information about relationships between two or more scan-paths on straightforward charts. The informativeness of the solution is analyzed using both artificial and real data.