The Effect of Tactile Noise on Stiffness Perception and Grip Force Control

Background: When interacting with the world, tactile and kinesthetic information are used to estimate the mechanical properties of objects and other external forces acting on our limbs. We combine both types of haptic feedback to form perception and regulate our grip force. Tactile feedback in the form of artificial tactor displacement induced skin stretch has been shown to increase the perceived stiffness and applied grip force. The objective of this project is to investigate the manner in which the human nervous system interprets tactile noise.

Methods: The kinesthetic and tactile information were generated by a haptic device and a 1 DOF skin-stretch device, respectively. In a stiffness discrimination task, participants received varying levels of both kinesthetic (load force) and tactile (skin stretch) feedback that depended linearly on their displacement against a virtual elastic object. In some of the trials, we added tactile noise, in the form of a sum of five sinusoid functions, to the linear tactile signal.

Results: Preliminary results (N=10) show that the addition of skin stretch, with and without noise, increased the perception of stiffness. Importantly, the addition of the tactile noise may increase the perceived stiffness more than skin stretch with no noise; however, this difference is not statistically significant and requires further investigation (planned sample size of N=25).

Conclusions: We reproduced previous findings that showed that artificial skin stretch augments stiffness perception. Our results suggest that the tactile noise was likely perceived as additional skin stretch, and therefore, further augmented the perceived stiffness.