Perceptual Force on the Wrist Under the Hanger Reflex and Vibration

The hanger reflex is a phenomenon that accompanies illusory force sensation and involuntary head rotation when the head is fastened with a wire hanger. This phenomenon is also observed on the wrist, and is expected to apply when using small and simple haptic feedback devices. However, issues of slow response and the requirement for large actuators still remain. Here, we discuss the discovery of a new phenomenon: the perceptual force from the hanger reflex is enhanced when a vibration is also presented. If we can control the strength of the perceptual force induced by vibration, a smaller, simpler, and higher response device might be achieved, because a vibrator can be controlled easily. This paper reports details of this phenomenon, and the effect of the frequency and amplitude of the vibration on the strength of the perceptual force. We observed that low frequency (50-100 Hz) vibrations efficiently enhanced the perceptual force, and that participants perceived a stronger perceptual force if the vibration of a greater amplitude was presented. These results suggest that the enhancement of the perceptual force is controllable and can be applied to construct a new type of wearable haptic device.