  Small form factor limits physical input space in earable (i.e., ear-mounted
wearable) devices. Off-device earable inputs in alternate mid-air and on-skin
around-ear interaction spaces using uni-manual gestures can address this input
space limitation. Segmenting these alternate interaction spaces to create
multiple gesture regions for reusing off-device gestures can expand earable
input vocabulary by a large margin. Although prior earable interaction research
has explored off-device gesture preferences and recognition techniques in such
interaction spaces, supporting gesture reuse over multiple gesture regions
needs further exploration. We collected and analyzed 7560 uni-manual gesture
motion data from 18 participants to explore earable gesture reuse by
segmentation of on-skin and mid-air spaces around the ear. Our results show
that gesture performance degrades significantly beyond 3 mid-air and 5 on-skin
around-ear gesture regions for different uni-manual gesture classes (e.g.,
swipe, pinch, tap). We also present qualitative findings on most and least
preferred regions (and associated boundaries) by end-users for different
uni-manual gesture shapes across both interaction spaces for earable devices.
Our results complement earlier elicitation studies and interaction technologies
for earables to help expand the gestural input vocabulary and potentially drive
future commercialization of such devices.
