1. Eye Tracker Performance Evaluation with ISO 9241 – Point and Click by Blinking and Dwelling Student: Matthew Conte Superviser: Prof Scott MacKenzie CSE Fall 2008
Introduction
An eye tracker used as a mouse is more suitable for handicapped users incapable of using a mouse where a user can move a cursor using his/her eyes. The performance of two ways of clicking with an eye tracker are evaluated in a user study.
Experiment
12 participants
4 Blocks of 17 targets
Block Layout:
-Target Widths: 16, 32 pixels
-Target Distances: 254, 509 pixels
Point and Click Technique:
-Click by Dwelling for 0.5 seconds
-Click by Blinking for 0.5 seconds
-Mouse (baseline condition)
Performance is measured in Throughput (bits/s) via ISO 9241 – part 2 [1], Mean Time per Trial (Target click) (ms), and Error Rate (% of target misses)
Questionnaire
A questionnaire given afterwards revealed that participants only had fatigue in the eyes and preferred to click by blinking because they prefer to choose when to click as click by dwelling produced involuntary clicks.
Apparatus
The Eyetech Digital Systems TM3 eye tracker (Figure 1a) provides a portable, ubiquitous and head-free solution for an eye tracker and can easily lie under a monitor or on top of a laptop computer as done in this experiment (Figure 1b).
Figure 4: Error rate for block layouts
Conclusion
Two clicking techniques for a head-free eye tracker were evaluated in a user study. Click by dwelling had greater throughput, less mean time per target click and higher error rate than click by blinking. Participants preferred click by blinking and improved through practice for a short task. Ideas for future experiments: longer tasks, different clicking techniques, different factors.
References
1. Zhang, X., and MacKenzie, I. S. (2007). Evaluating eye tracking with ISO 9241–Part 9. Proceedings of HCI International 2007, pp
Results
Click by dwelling produced significantly higher throughput, less time per target click, and higher error rate than by blinking. Results were most significant in mean time per target click (F1,11 = , p < .0001). (Figure 2).
Figure 2: Mean time per target click for each technique
Figure 1a: EyeTech Digital Systems TM3 eye tracker
Prolonged Use
Prolonged use of using an eye tracker has significantly lowered participants’ error rate for a short task of under 5 minutes (Figure 3).
Target Size and Distance
Error rates reduced by 50% when target sizes were larger and distances were smaller (Figure 4).
Figure 1b: Participant using eye tracker on top of a laptop computer
Figure 3: Error rate for each block of targets