Measuring gaze overlap on videos between multiple observers

For gaze-based training in surgery to be meaningful, the similarity between a trainee's gaze and an expert's gaze during performance of surgical tasks must be assessed. As it is difficult to record two people's gaze simultaneously, we produced task videos made by experts, and measured the amount of overlap between the gaze path of the expert surgeon and third-party observers while watching the videos. For this investigation, we developed a new, simple method for displaying and summarizing the proportion of time during which two observers' points of gaze on a common stimulus were separated by no more than a specified visual angle. In a study of single-observer self-review and multiple-observer initial view of a laparoscopic training task, we predicted that self-review would produce the highest overlap. We found relatively low overlap between watchers and the task performer; even operators with detailed task knowledge produce low overlap when watching their own videos. Conversely, there was a high overlap among all watchers. Results indicate that it may be insufficient to improve trainees' eye-hand coordination by just watching a video. Gaze training will need to be integrated with other teaching methods to be effective.