## 5 Results
### Taxonomy of Wrist and Thumb-to-Index Touch Gestures  
To further understand wrist and thumb-to-index touch gestures used to perform HAR interactions, we considered the following three dimensions in our analysis. We were inspired and adopted/modified these dimensions from previous studies [35; 50; 51], and grouped them by the specifics of both wrist and thumb-to-index touch gestures:  
1. Complexity (see Figure 4) identifies both touch and wrist gesture as either (a) simple or (b) complex. We define simple gestures as gestures that are performed using only one gesture (e.g., wrist or touch gesture). For example, moving the wrist downwards toward the palm to perform downward flexion and/or using the thumb to press any of the soft foam buttons are identified as simple gestures. Gestures performed using two or more distinctive gestures are identified as complex gestures (e.g., pressing a soft foam button followed by moving the wrist downwards toward the palm). We adopted this dimension from [52]. 2. Structure (see Figure 5) represents the relative importance of the wrist and touch gestures in the elicitation of HAR gestures, with seven categories: (a) wrist (b) touch (button one), (c) touch (button two), (d) touch (button three), (e) touch (button one) and wrist, (f) touch (button two) and wrist, and (g) touch (button three) and wrist. We modified this category from the taxonomy of [PERSON] and [PERSON] [51]. For example, for touch only category, the tap or hold gesture was performed using any one of the three buttons. 3. Action (see Figure 6) groups the gestures based on their actions rather than their semantic meaning with five categories: (a) scroll, (b) swipe, (c) tap, (d) hold, and (e) compound. We adopted and modified this classification from [PERSON] et al. [35], who used these dimensions to define user-designed single-hand microgestures without any specific domains. For example, downward flexion and upward extension were grouped as scrolls, while leftward flexion and rightward extension were grouped as swipes. Figure 4: Frequency distribution of complexity of gestures in each category. Simple gestures were highly preferred for discrete tasks. Figure 5: Observed percentages of wrist and touch gestures for HAR interactions. Button one was highly preferred for both simple and complex gestures. Simple wrist gestures were preferred for continuous tasks and simple touch gestures for discrete tasks (shows a clear influence of prior experience). Simple gestures were highly performed for both discrete (82.75%) and continuous tasks (49.78%). Interestingly, participants preferred to use simple touch gestures (51.05% vs. 31.70%) for discrete and simple wrist gestures (36.58% vs. 13.2%) for continuous tasks. Similarly, complex gestures (50.22% vs. 17.25%) were also preferred for the continuous tasks. These results were confirmed by a one-way ANOVA test. We found a significant effect for complexity (\(F_{(1,25)}=73.274\), \(p=0.000\)) as our participants preferred simple gestures to perform discrete HAR tasks. Our participants preferred to use button one on the index finger to perform both simple and complex gestures for all 27 tasks. For example, for the discrete tasks, 27.51% (button two: 23.78%; button three: 17.01%) of gestures were performed using button one. Similarly, button one was involved in nearly 19.91% (button two and wrist: 17.97%; button three and wrist: 12.34%) of complex gestures for the continuous tasks. A one-way ANOVA test revealed a statistically significant effect for touch inputs using button one for discrete tasks (\(F_{(1,25)}=14.275\), \(p=0.001\)) and button one and wrist inputs for continuous tasks (\(F_{(1,25)}=23.773\), \(p=0.000\)). Compounds (all 27 tasks) were the most common out of the five action types, mainly used to perform continuous tasks, particularly the object transformation tasks.