Power Law Based "Out of Body" Tactile Funneling for Mobile Haptics.

''Out of body" tactile illusions can serve as a tool to exploit the limitations of human perception to augment the information displayed in the mobile haptic devices. The objective of this study was to establish a psychophysics based mathematical relationship between the intensity of physical and phantom stimulus rendered "out of the body." In order to achieve this objective, three experiments were conducted, the first experiment was to compare three existing algorithms (linear, logarithmic, and square) defined for "on the body" when extended to "out of the body," the second experiment was to test the pertinence of the best performing algorithm from first experiment, and the third experiment was designed to identify an ideal mathematical relation using psychophysical studies. Fifteen subjects participated in the experiments and the physical stimuli were provided to the index fingers of both the hands such that the phantom stimulus was perceived in the mid-air between them. Results of the first experiment depicted that the "square algorithm" was the best among the three. Results of the second experiment proved "square algorithm" to be better than other two algorithms but not ideal to define mathematical relation for "out of body" tactile funneling illusion. Results of the third experiment established a novel and better performing algorithm using "power relationship" between the intensity of physical and phantom stimulus leading to "out of body" tactile funneling. Although this paper defines the power relationship between the phantom and physical stimulus intensity, the relationship between location of phantom stimulus and the physical stimulus intensity remains the future scope of this study.