## 3 Methods
### Experimental Setup and Procedure  
The experimental environment is shown in Figure 3. In a quiet laboratory space, participants wearing AR glasses were positioned in a standing posture 1.5 m away from the wall. The distance from the participant to the wall was determined based on the typical distance between the surgeon and the display in the actual operating room to which the authors belong. On the wall, a 60 cm by 60 cm display area was set to show test tracks. The center of the display area was 165 cm from the floor. The test track consisted of two squares with different colors and a white pathway connecting two squares. A blue square represented a starting area, and a yellow square represented a goal area. Independent of the test track, a cursor controlled by the head motion appeared on the display area.  
The participants manipulated the cursor by using head movements through the white pathway from the start area to the goal area. The measurement was started when the cursor left the start area and advanced to the white pathway. The time to complete steering through the pathway without being out of bounds (_MT_), the number of times the cursor deviated from the pathway (the number of errors), and the cursor's movement speed were sampled at 60 Hz. The measurement was terminated when the cursor reached the goal area or went out of the pathway before reaching the goal area. When the cursor reached the goal area, the displayed test track disappeared and the next randomly selected test track was displayed for the next trial. If the cursor went out of the track, an error was recorded, and the measurement was reset. The color of the cursor was changed according to the status for the purpose of giving visual feedback to participants.  
Figure 3: Experimental environment. A 60 cm by 60 cm area was used to show test tracks (**left**). Participant stood 1.5 m away from the display area (**right**).  
After completing the informed consent process, the participants were asked to practice wearing and operating the AR glasses to get used to them. The experimenter explained the range of motion of the AR glasses' headband and asked the participants to put on the AR glasses by themselves so that their nose and head would not hurt and they could see the AR screen in front of them. Next, as a preliminary trial, we had the participants practice steering through nine different test tracks with the cursor to get used to the task operation. Once the practice was completed, we had the participants run the main trial. When the participants completed 48 tasks, half of the 96 test tracks, they were asked to remove their AR glasses and take a break.  
After the participants completed all 96 tasks, they took off their AR glasses and filled out the questionnaire. The flow from the start of the first practice trial to the end of filling out the questionnaire was taken as one set, and three sets were conducted in this experiment.  
The questionnaire regarding the difficulty of the tracking task was collected for each of the 24 directions of operation. Each questionnaire was evaluated on a seven-point scale. The larger the number, the more difficult the task was perceived.