Visual Exploration Patterns in Information Visualizations 

Role

User Researcher, Information Visualization. 

Supervised by

Cesar Hidalgo, MIT - Areej Alwabel, MIT & KACST

Jumana Almahmoud, Saleh Albeaik, Tarfah Alrashed, and Almaha Almalki. "Visual Exploration Patterns in Information Visualizations: Insights from Eye Tracking." In International Conference on Social Computing and Social Media, pp. 357-366. Springer, Cham, 2017. pdf

Challenge

One of the common problems associated with measuring the usability of information visualizations is understanding human factors of visual perception and cognitive processing in interacting with dynamic data graphs that are commonly used in social computing applications.

Solution

proposes a framework of eye tracking metrics related to interacting with information visualizations which demonstrate the underlying relationships between human factors in gaze metrics and information visualization design factors. Design implications and issues relating to the investigation of these metrics are also discussed.

Exploratory Eye-Tracking Study

Inspired by research methodologies originally developed for analyzing graphic visualizations, we explore eye-tracking methods that measure various static and dynamic aspects of visual perception, and their relations to an underlying cognitive processes. The eye fixations and visual scanning patterns allow us to analyze and quantify what information visualization elements viewers encode, retrieve, and recall from memory. In this exploratory study, we look at the different ways in which we can analyze people's eye-movements and responses as they interact with information visualizations.

A total of 23 participants (8 females, 15 males) participated in the experimental study. All of the participants were recruited from the local communities in Riyadh, Saudi Arabia with an average age of 28.09 years (SD = 5.18 years). All participants had bachelor's degree or higher. The participants had normal color vision. Table 1 shows the demographics of participants in the study's sample.

For the eye-tracking study of our experiment, we used a Tobii X120 stand-alone eye-tracking system with participants seated approximately 60cm from a 23 inch monitor (resolution:1920 x 1080 pixels). Tobii studio V 3.4 was used for recording and analysis. Sessions were conducted in an office setting where noise was reduced compared to the usual setting within the space. The process of establishing the framework of mapping gaze metrics involved merging taxonomy with the taxonomy of gaze metrics. Table 1 describes the metrics.

Procedure A single session of the experiment took between 15 to 20 minutes for each participant. At the beginning of an experimental session, participants were introduced to the session by giving them an overview of what eye-tracking is and the nature of the tasks they will be performing. When the session starts for each user, we conducted a randomized 5-point calibration procedure to establish the 3D coordinates of the eyes. At regular intervals, a drift check was performed and, if necessary, recalibration took place, and optional breaks were offered to participants. This exploratory study involved two sections; the first one prompts the user to perform informational tasks in which there were asked a set of questions and were asked to look for the answer using the stimuli they were exposed to. The second one involved a navigational task in which the users were asked to explore a webpage from the visualization platform. The following images are the visual triggers displayed to the user.

The findings demonstrate that there is a marked difference between the fixation patterns and their corresponding spatial distribution in different visualizations as expected; however, our understanding of which visual elements in the information visualization contribute to this difference in fixation patterns, and which human factors help explain the usability issues or the overall user experience is inadequate. These are areas for further investigation that can be guided by the proposed framework described in the Framework section.

In the treemap pattern, most gaze areas correspond to labels possibly indicating that users were searching for their target. In the convergence phase, the treemap visualization pattern presented to our participants showed gravitation of eye gaze towards the targets, and the competing target. More specifically, users aggregate eye gaze accumulated at labels of the target and the competing target.

Similar patterns appeared in the stacks visualization pattern. Users’ aggregate eye gaze were gravitated towards targets. However, in this case, visual elements that encode information users were expected to compare had low color contrast. In this heat map, eye gazes were attracted to labels of actual target and competing target, and as well attracted to a label of another area similar in visual properties (similar background color) with target and competing target, and attracted to the separating line between the three areas.

Based on the eye tracking results presented in the preceding sections, we summarize in this section the key observations from our study. This work presents an outline of mapping eye-tracking metrics to usability metrics for investigating interactive information visualizations. The emphasis was on the dimensions of design factors, human factors of perception and cognition, and task. In addition, we characterize visualization design considerations that are related to individual and aggregate gaze metrics, including fixations, saccades and scan paths. Based on insights from our exploratory eye tracking study and previous research, we are able to offer framework to support usability evaluations based on existing conventional visualization design guidelines.