Comparison of reality and illusion of wetness on soft materials and the multisensory perceptual space of wetness illusion

Skin contact with cold objects can induce the perception of wetness, known as the wetness illusion, even in the absence of actual moisture. However, the differences between wetness perceived from moisture and cooled-dry soft materials and how the material parameters affect the wetness illusion from cooled-dry soft materials remain unclear. This study recruited 12 women and 12 men to touch paired moisture and dry fabrics to compare the prescription and intensity of wetness, suggesting that the wetness illusion focused more on roughness and stickiness while the wetness of moisture fabrics sensed more on coldness. Another 12 women touched cooled-dry materials with different temperatures (10°C and 15°C), thicknesses (0.75/0.73 and 1.99/1.96 mm), and dynamic friction coefficients (mean coefficient of friction) (0.17 and 1.88), rating on wetness dissimilarity and intensity of wetness, coldness, softness, and roughness. Data were illustrated in a two-dimensional space by multidimensional scaling, in which dimension 1 represented the haptic perception in wetness, most related to the mean coefficient of friction, and dimension 2 represented the coldness perception in wetness, most related to temperature. Overall, the mean coefficient of friction and the temperature of the material had a strong influence on the wetness illusion, while the thickness had less impact. This study improves the understanding of wetness illusion and sheds light on the reproduction of wetness perception in multisensory augmented virtual reality, such as immersive gaming and virtual dress fitting.