## 2 Methodology
### Initial Expert Pre-Selection of Gestures to Match Commands  
For each command (Table 3), three researchers pre-selected eight of the designed microgestures (Figure 1, Table 2) that best matched the command metaphorically. The purpose of pre-selecting eight gestures was to reduce the cognitive demands on participants, so they would not have to review all 33 microgestures when assigning microgestures to a command. Differences between experts were resolved with discussion.  
Microgestures were mapped to 20 commands (Table 3) based on existing lexicons; mapping was not based on physical (i.e., shaking the HMD) [43], symbolic (i.e., drawing a letter O with fingertips) [46], or abstract (i.e., arbitrary gesture) mappings that could hinder recall or reliable performance. Commands considered to be opposites of each other were mapped to a similar gesture performed in opposite directions [43]. For example, a flick to the right was the most common gesture for the \"next\" command while a flick to the left was the gesture mapped to the \"previous\" command. Furthermore, depending on the command, microgestures could be performed in discrete or continuous movements. For example, the \"duplicate\" command was designed as a discrete movement while the \"adjusting volume\" command was designed as a continuous movement. The eight microgestures pre-selected for each command are listed in Table 3.  
\begin{table}
\begin{tabular}{l} \hline \hline
**Gesture Description** \\ a. Grab/expand with the neutral forearm \\ b. Grab/expand with the pronated forearm \\ c. Pinch/expand with the neutral forearm \\ d. Index finger circles CW/CCW with the pronated forearm \\ e. Index finger circles CW/CCW with the neutral forearm \\ f. Thumb slides on index finger with the neutral forearm \\ g. Thumb slides on the middle finger with the neutral forearm \\ h. Thumb taps on the index finger with the neutral forearm \\ i. Thumb taps on the middle finger with the neutral forearm \\ j. Index fist taps on the table with the pronated forearm \\ k. Index finger taps on the table with palm down on the table \\ l. Palm taps on the table with palm down \\ m. Fist taps on the table with the pronated forearm \\ n. Fist posture rotates from the pronated forearm to the neutral forearm \\ o. Palm posture rotates from neutral forearm to pronated forearm \\ p. Forming okay posture from palm posture, with the neutral forearm \\ q. Forming okay posture from fist posture, with the neutral forearm \\ r. Index finger scratches toward/away with the pronated forearm \\ s. Index finger scratches toward/away with the neutral forearm \\ t. Index and middle fingers scratch toward/away, pronated forearm \\ u. Index and middle fingers scratch toward/away with the neutral forearm \\ v. Palm scratches toward/away with the neutral forearm \\ w. Index finger scrolls left/right with the pronated forearm \\ x. Index and middle fingers scrolls left/right with the pronated forearm \\ y. Palm scrolls left/right with the pronated forearm \\ z. Index finger points forward with the neutral forearm \\ aa. Index finger points forward with the pronated forearm \\ ab. Index and middle fingers point forward with the neutral forearm \\ ac. Index and middle fingers point forward with the pronated forearm \\ ad. Curled palm with the neutral forearm \\ ae. Curled palm with the pronated forearm \\ af. Fist posture with the neutral forearm \\ ag. Fist posture with the pronated forearm \\ \hline \hline \end{tabular}
\end{table}
Table 2: The literal description of 33 designed microgestures.