Tactor Placement in Wrist Worn Wearables

Vibro-tactile stimulation has been revealed as a potentially effective means to deliver spontaneous notifications like alerts to recipients that are focused on other tasks (although only at very low bit rates, and depending on the place at which the tactors are placed). This work addresses the issue of the amount of information that can be perceived via stimuli coming from wrist worn tactors, given the recipient is not expecting or attentive to the potential occurrence of an alert. Assuming apparel like wrist watches with embedded tactors to represent the alert delivery platform, we investigate - respecting physiognomical properties of tactile perception the effectiveness of different tactor placements. We compare the case of embedding 4 tactors underneath the “face” of the wrist watch, against the case of embedding it into the wristband (“wrist”). A user study of 1,823 trials has been conducted involving recipients exposed to different levels of engagement in a certain activity. The experiments show, that the amount of information perceived via spontaneous tactile alerts ranges from 1.90–2.49 bits at low, to 1.59–2.41 bits at high levels of engagement. The “wrist” tactor placement achieves a 41.6 % higher perception bit rate than the “face” tactor placement.