12 Contact Location Trajectory on the Fingertip as a Sufficient Requisite for Illusory Perception of Haptic Shape and Effect of Multiple Contacts

Abstract

This chapter seeks to demonstrate that haptic curvature perception can result solely from the trajectory of the deformed region of the fingertip due to contact with an object during tactile exploration. To test this hypothesis, we built a servo controlled 2-degree-of-freedom spherical mechanism called a Morpheotron. This device operates by rolling a flat plate on the fingertip during the exploration of a virtual surface while eliminating all other cues that are normally present, including kinesthetic cues. In carrying out the experimental protocols described herein, we found that subjects were able to perform curvature discrimination at levels comparable to those achieved when using direct manual contact with real objects, and that the highly simplified stimulus provided was able to give the illusion of touching three dimensional surfaces.