In the Burning Hand Illusion (BHI), participants perceive illusory heat as they observe virtual flames on their hands in Augmented Reality. In this study, we investigate the role of stimulus location within peri-hand space and its resemblance to a realistic fire in the emergence of the illusion. Additionally, we examine the associated autonomic nervous responses, quantified through skin conductance and pupil dilation responses. We used the following four conditions: (A) Realistic flames on the right hand paired with the sound of a burning torch; (B) Green, flame-like visuals on the hand paired with a sound that does not evoke fire but is spectrally matched to the sound of the burning torch; (C) Realistic flames between the hands; and (D) Green, flame-like visuals between the hands. Sixteen out of twenty-five participants reported feeling heat in condition (A), while seven reported a sensation of warmth in condition (C). Condition (B) introduced ambiguity, as participants reported warmth as well as cold sensations, but overall, fewer participants reported thermal illusions. No participants reported thermal illusions in (D). These findings suggest that both the location and resemblance of the flames significantly influence the emergence of the BHI, with the response diminishing as the flames become less plausible or not placed on the actual hand. Skin conductance responses were highest in condition (A) and lower in condition (C), with the lowest responses observed in conditions (B) and (D). Pupil dilation responses were largest in conditions where the flames were directly on the hand. The observed autonomic responses reinforce the notion that the BHI elicits physiological effects that parallel those of real thermal stimuli. This provides evidence that the virtual fire in the BHI is sufficiently plausible to be perceived as affecting the hand, and is consequently processed by the brain’s homeostatic emotional systems.

Bezel-based gestures expand the interaction space of touch-screen devices (e.g., smartphones and smartwatches). Existing works have mainly focused on bezel-initiated swipe (BIS) on square screens. To investigate the usability of BIS on round smartwatches, we design six different circular bezel layouts, by dividing the bezel into 6, 8, 12, 16, 24, and 32 segments. We evaluate the user performance of BIS on these layouts in an eyes-free situation. The results show that the performance of BIS is highly orientation dependent, and varies significantly among users. Using the Support-Vector-Machine (SVM) model significantly increases the accuracy on 6-, 8-, 12-, and 16-segment layouts. We then compare the performance of personal and general SVM models, and find that personal models significantly improve the accuracy for 8-, 12-, 16-, and 24-segment layouts. Lastly, we discuss the potential smartwatch applications enabled by the BIS.

In this paper, we propose and investigate a new text entry technique using micro thumb-tip gestures. Our technique features a miniature QWERTY keyboard residing invisibly on the first segment of the user's index finger. Text entry can be carried out using the thumb-tip to tap the tip of the index finger. The keyboard layout was optimized for eyes-free input by utilizing a spatial model reflecting the users' natural spatial awareness of key locations on the index finger. We present our approach of designing and optimizing the keyboard layout through a series of user studies and computer simulated text entry tests over 1,146,484 possibilities in the design space. The outcome is a 2×3 grid with the letters highly confining to the alphabetic and spatial arrangement of QWERTY. Our user evaluation showed that participants achieved an average text entry speed of 11.9 WPM and were able to type as fast as 13.3 WPM towards the end of the experiment.

We introduce FingerT9, leveraging the action of thumb-to-finger touching on the finger segments, to support same-side-hand (SSH) text entry on smartwatches. This is achieved by mapping a T9 keyboard layout to the finger segments. Our solution avoids the problems of fat finger and screen occlusion, and enables text entry using the same-side hand which wears the watch. In the pilot study, we determined the layout mapping preferred by the users. We conducted an experiment to compare the text-entry performances of FingerT9, the tilt-based SSH input, and the direct-touch non-SSH input. The results showed that the participants performed significantly faster and more accurately with FingerT9 than the tilt-based method. There was no significant difference between FingerT9 and direct-touch methods in terms of efficiency and error rate. We then conducted the second experiment to study the learning curve on SSH text entry methods: FingerT9 and the tilt-based input. FingerT9 gave significantly better long-term improvement. In addition, eyes-free text entry (i.e., looking at the screen output but not the keyboard layout mapped on the finger segments) was made possible once the participants were familiar with the keyboard layout.