Scaling of Apparent Viscosity

Observers made numerical judgments of the apparent viscosities of silicone liquids whose absolute viscosities ranged from 10.3 to 95,000 centipoises. Judgments were made by three procedures: shaking or turning a bottle containing the liquid, stirring the liquid with a rod with the eyes blindfolded, and stirring with the eyes open. For all these methods of judging, apparent viscosity was found to grow as the absolute viscosity raised to a fractional power. The exponents ranged from 0.42 to 0.46. The perception of viscosity follows the psychophysical power law that seems to govern prothetic perceptual continua.