Haptic Perception of Viscosity
Viscosity is a liquid’s resistance against flow. Using a discrimination experiment, the human ability to distinguish between different viscosities was measured over the range of 200–20,000 mPa.s. Eight blindfolded subjects stirred pairs of different silicone oils using a wooden spatula and had to indicate the “thicker” of the two. The viscosity of the liquids was measured seperately using a rheometer. Weber fractions for discrimination ranged from 0.3 at high viscosities to almost 1 at the lowest viscosity. For the higher viscosities, discrimination could be described as Weber-like, but for the low viscosities, there seemed to be a floor effect for the absolute threshold. The characterisation of the discrimination threshold as a function of viscosity is of fundamental interest in perception research, but also of practical value for designers of haptic devices capable of displaying viscosity.
KeywordsKinaesthesia Dynamic touch Thresholds Liquid Weber fraction
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