## 5 User Study
### Procedure  
We recruited 20 graduate students on campus as participants, including 5 men and 15 women, who have normal color vision (no color blindness) and are right-handed. Fifteen of them knew the adjacency matrix in graph visualization, and six had experience in immersive analytics. We used a between-subjects design, and the participants were randomly assigned to two groups. Ten students participated in the experimental Scene1-MVF (two men, eight women), and the other 10 students participated in the experimental Scene2-EBC (three men, seven women). The participants wore a VR HMD display and sat on a chair with their hands about 15 cm in front of the Leap Motion (Figure 5). The participants were first introduced to the basic knowledge of graph visualization, adjacency matrix mapping rules, multi-attribute mapping rules, and experimental tasks, then introduced to the essential operation in the virtual environment, and a group of pre-experiments were conducted the same VR experimental scenario. The pre-experiment was conducted in the order of small, medium, and large clusters to help the users gradually adapt to the difficulty. The formal experiment consisted of 9 clusters (three small, three medium, and three large). Only a pinch gesture was used in the whole experiment. The participants were advised to take a 5-10 min break in the middle of the experiment, and each participant spent about 60 min completing the experiment. Each participant completed 4 tasks \(*\) 9 clusters = 36 tasks in this scenario. Finally, we collected 20 participants \(*\) 2 techniques \(*\) 36 tasks = 1440 trials. A task panel in VR includes the task number, task content, and a button that controls the start and end of the timer (Figure 6). After the user understands the task, they pinched \"Start\" button in the task panel to start timing, pinched the name tag of the node to select the task answer, and pinched the \"Submit\" button in the task panel to end timing and submit the answer after finishing the task. If the submitted answer is empty, then the submission cannot be made, and the timing will not end until one or more answers are successfully submitted. Once a trial is completed, the subsequent trial is displayed automatically until all four cluster trials have been conducted, and then, the next cluster with its tasks would appear. We asked the participants to complete tasks as quickly and accurately as possible, with each task completion time measured by the user pinching on the \"Start\" button and  
Figure 5: Hardware setup and experimental program interface. Figure 6: Task panel for timing in VR. \"Submit\" buttons and accuracy as measured by the number of correct tasks in the group. After the user completes the task, the program automatically records and calculates the data. At the end of the experiment, the users were asked to experience the other model and then fill out Likert scales to reflect their subjective satisfaction. The questionnaire aims to evaluate the influence of two factors (position mapping and attribute occurrence quantity) on location, comparison, and comprehension. Q1-Q3 belong to the position factor, Q4-Q6 belong to the attribute occurrence quantity factor, and belongs to the preference of the two models. Except for Q7, each question has five choices: strongly disagree (1), disagree (2), not sure (3), agree (4), and strongly agree (5). These questions include the following:  
* **Q1:** You think that the position mapping of the author and attributes is helpful for you to locate the attribute value. * **Q2:** You think that the position mapping of the author and attributes is helpful for you to compare attribute values. * **Q3:** You think that the position mapping of the author and attributes is helpful for you to understand the relationship between author and their attributes. * **Q4:** You think that the attribute occurrence number is helpful for you to locate attribute values. * **Q5:** You think that the attribute occurrence number is helpful for your to compare attribute values.