Spatial patterns of cutaneous vibration during whole-hand haptic interactions

Significance In animals and machines, our understanding of tactile function has hitherto been based primarily on information collected at, or near to, the region of contact of a tactile probe with an object. Using the human hand as a case in point, we show that during natural interactions with ordinary objects, mechanical energy originating at finger contact propagates through the whole hand, and that vibration signals that are captured remotely contain sufficient information to discriminate between gestures and between the touched objects. Our results shed light on possible tactile processes in humans and animals and may yield advances in tactile sensing for robotic manipulation or lead to novel paradigms for wearable computing. We investigated the propagation patterns of cutaneous vibration in the hand during interactions with touched objects. Prior research has highlighted the importance of vibrotactile signals during haptic interactions, but little is known of how vibrations propagate throughout the hand. Furthermore, the extent to which the patterns of vibrations reflect the nature of the objects that are touched, and how they are touched, is unknown. Using an apparatus comprised of an array of accelerometers, we mapped and analyzed spatial distributions of vibrations propagating in the skin of the dorsal region of the hand during active touch, grasping, and manipulation tasks. We found these spatial patterns of vibration to vary systematically with touch interactions and determined that it is possible to use these data to decode the modes of interaction with touched objects. The observed vibration patterns evolved rapidly in time, peaking in intensity within a few milliseconds, fading within 20–30 ms, and yielding interaction-dependent distributions of energy in frequency bands that span the range of vibrotactile sensitivity. These results are consistent with findings in perception research that indicate that vibrotactile information distributed throughout the hand can transmit information regarding explored and manipulated objects. The results may further clarify the role of distributed sensory resources in the perceptual recovery of object attributes during active touch, may guide the development of approaches to robotic sensing, and could have implications for the rehabilitation of the upper extremity.