Visual Analysis of Eye Movement Data with Fixation Distance Plots

Abstract

Eye tracking has become an increasingly important technology in many fields of research like marketing, psychology, human-computer interaction, and also in visualization. Understanding the eye movements of people while solving a given task can be of great support to improve a visual stimulus. The challenging problem with this kind of spatio-temporal data is the difficulty to provide a useful visualization that can provide an overview about the fixations with their durations and sequential order, the saccades with their orientations and lengths, but also the distances of several fixations in space. Traditional visualizations like gaze plots - showing the stimulus in its original form overplotted with the scan paths - typically produce vast amounts of visual clutter and make a visual exploration of the eye movement data a difficult task. In this paper we introduce the fixation distance plots that place the fixation sequences to a horizontal line of color coded and differently thick circles while showing additional saccadic information. Moreover, the user can apply distance thresholds that indicate if fixations are within a certain distance allowing to get an impression about the spatial stimulus information. We illustrate the usefulness of the approach by applying it to eye movement data from a formerly conducted eye tracking experiment investigating route finding tasks in public transport maps.