Tactile mouse generating velvet hand illusion on human palm

Abstract

To enhance virtual reality (VR) generated by tactile displays, we have focused on a novel tactile illusion, called the Velvet Hand Illusion (VHI). In VHI, moving two parallel wires back and forth between the two hands leads humans to perceive a velvet-like surface between their hands. In earlier studies, we revealed that the intensity of VHI could be controlled by a ratio ( r/ D), where r and D are the wire stroke and wire distance, respectively. According to these findings, we investigate in this study whether a common tactile display is able to produce VHI, and whether the ratio can also control VHI intensity. We prepare a dot-matrix display as a tactile display in which moving one line of the display’s pins is considered as a wire pattern. We investigate the VHI intensity with regard to changing the stroke r and the line distance D using paired comparison. Experimental results show that the VHI intensity is increased or decreased by changing r and D. We conclude that VHI can be created by the tactile display, and the intensity of VHI is controlled by changing the ratio of r/ D.

Describing the Sensation of the ‘Velvet Hand Illusion’ in Terms of Common Materials

“…This continuous change allowed us to identify materials that are similar to each level of the illusion intensity. We predicted that when participants feel a stronger illusory sensation, the sensation would be evaluated as softer, smoother, slipperier, and more favorable and similar to the sensation for velvet material rather than metallic wires as subjectively described in past studies [2]- [6], [8].…”

“…Still, the subjective nature of VHI, i.e., the quality and magnitude of the illusory sensation felt during VHI, remains vaguely characterized. For example, the sensation felt during VHI has been described as velvety, "smooth and glistening," or oily [3]- [6], [8] as based on introspective reports, but the correctness and generality of these subjective descriptions have not been experimentally clarified. While some researchers investigated tactile ratings of smoothness, softness, and pleasantness experienced during VHI [7], [9], [10], there remains a possibility that the observed ratings might partially reflect the properties of the stimulus materials per se (e.g., materials moved between both hands, or materials placed on the other side of the wire from the hand).…”

Edge angle perception precision of active and passive touches for haptic VR using dot-matrix display

“…In this section, we explain the tactile mouse developed for the human palm (Rajaei et al, 2016). We adopted the mouse-type display because it is very easy for subjects to move it and touch a virtual object with natural motions.…”

“…This is why we focus on the palm, which has an approximately 13-mm two-point threshold (Johansson and Vallbo, 1983;Fox, 2002). As one approach to this problem, in our previous study (Rajaei et al, 2016), we introduced a dot-matrix display called SC10 with a pin distance of 2.4 mm, which is sufficiently smaller than 13 mm. We applied this to our tactile mouse exhibiting convex dot patterns on the palm to evaluate the dot-matrix display in VR, since the only difference between the fingertip and the palm is the receptor distribution.…”

Formulation of tactile Gestalt to express variation in velvet hand illusion caused by out-of-phase cycles of two wires

“…So far, we have elucidated factors of VHI intensity control using psychophysical experiments (Ohka et al, 2010;Rajaei et al, 2012;2016), and human brain network causing VHI using psychophysiology (Rajaei et al, 2018). Especially, in the preceding study (Rajaei et al, 2016), it is shown that two lines caused on a dot-matrix display generate VHI when experimental participants put their hands on the display. This study is a pioneer for usage of VHI on VR devices.…”