Surface haptic feature attenuation due to contact on opposing surface

In fingertip interaction with a virtual surface, the illusion of a protruding bump can be created even in the absence of out-of-plane forces or motions, by presenting just the lateral forces associated with sliding over a bump [19]. We found that when a virtual bump on one side of a planar haptic display surface is explored with a fingertip, adding contact with the opposing side of that surface as well (pinch grip) decreases the virtual bump's perceived height. Using two motor-driven sliding contact surfaces (one for either side of the display plane), we determined when a bump traversed with the index finger alone subjectively matched a comparison bump explored with simultaneous thumb contact on the opposing side (the point of subjective equality, or PSE). The decrease in perceived bump height due to opposing surface contact was on the order of 10%.