Tactual perception of liquid material properties

- Orally and manually perceived viscosity are quite comparable.
- For discrimination of different levels of viscosity a Weber fraction of ∼0.3 is found.
- Wetness perception depends on thermal and mechanical cues.
- For discrimination of different levels of wetness a Weber fraction of ∼0.4 is found.

In this paper, studies into the tactual perception of two liquid material properties, viscosity and wetness, are reviewed. These properties are very relevant in the context of interaction with liquids, both real, such as cosmetics or food products, and simulated, as in virtual reality or teleoperation. Both properties have been the subject of psychophysical characterisation in terms of magnitude estimation experiments and discrimination experiments, which are discussed. For viscosity, both oral and manual perception is discussed, as well as the perception of the viscosity of a mechanical system. For wetness, the relevant cues are identified and factors affecting perception are discussed. Finally, some conclusions are drawn pertaining to both properties.