If a study is executed with a single participant, a moderator view is crucial. While using another tool, allowing this view, it happened to me, that one eye was not caught by an eye-tracker, it caused eye-tracking artifacts resulting in not usable data. I could realize it and instruct a participant to blink a few times, which restored eye-tracking. Also, by watching real-time eye-gaze it is possible to ask questions after a task according to what was actually seen by a participant.
If a study is executed with a single participant, a moderator view is crucial. While using another tool, allowing this view, it happened to me, that one eye was not caught by an eye-tracker, it caused eye-tracking artifacts resulting in not usable data. I could realize it and instruct a participant to blink a few times, which restored eye-tracking. Also, by watching real-time eye-gaze it is possible to ask questions after a task according to what was actually seen by a participant.