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Matjaz Jogan, Jeffrey Martin; Visual perception of liquids in motion. Journal of Vision 2018;18(10):223. doi: 10.1167/18.10.223.
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© ARVO (1962-2015); The Authors (2016-present)
Viscosity of liquids can be readily perceived by our sense of vision. In this work we studied human perception of viscosity of liquids in motion. We measured the Weber fractions and estimated the perceptual bias due to a change in appearance. Stimuli were videos of Newtonian silicone oils that were pumped from a dispenser and landing on an inclined surface. There were 21 calibrated oil samples in total. Polydimethilsiloxane viscosity standards and a rheometer were used to achieve the target viscosities. Observes participated in a two-alternative forced choice task. In each trial they observed a reference and a test video and had to state in which video the liquid looked thicker. The responses from two separate sessions were used to determine the Weber fractions at five reference viscosities for i) transparent (N=57) and ii) opaque (N=57) stimuli. In a third session, reference stimuli were opaque and test stimuli were transparent (N=110). Responses from this session determined the perceptual bias due to change in appearance. Reference viscosities ranged from 500 to 16,000 centipoise (cP), and each observer saw each of the unique reference/test pairs once. Psychometric functions were fit to total data from all observers. Weber fractions were approximately 0.6 for medium thickness, but showed an increase for low (500 cP) and high (>3,500 cP) viscosities. Visual appearance of the liquids modulated how thick they looked. At low viscosity, opaque liquids appeared up to two times more viscous than transparent liquids. This bias got proportionally smaller as the thickness of the reference increased. At the highest reference viscosity (16,000 cP), opaque liquids appeared slightly less (1,660 cP) viscous than transparent liquids. Our results suggest that perception of viscosity is modulated by visual appearance, and particularly so in the range where discrimination is poor.
Meeting abstract presented at VSS 2018
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