Representation of softness sensation using vibrotactile stimuli under amplitude control

An experimental study was done to examine the relationship between vibrotactile amplitude displacement and softness sensation. Merkel Disk behavior relative to softness sensation was studied under psychophysical experimentation of human participants. Restrictions are carefully applied on contact area spreading so that vibration will be the only factor that would induce a sensation. A vibrotactile device was excited at constant frequency and its amplitude is adjusted at different levels to alter the amount of skin displacement. Volunteers participated in a two-alternative force choice experiment were ask to compare the perceived softness difference between voice coil and silicone rubber. Statistical analysis on the responses of participants showed a decline of spring constant. It was interesting to note, that even though contact area was significantly restrained participants were still able to discriminate softness sensation form vibrotactile stimulation. Such observation possibly shows that illusion of contact area spread rate can be reproduced by vibrotactile stimulation.