The fact that humans can’t feel wetness seems ridiculous at first. You may have even read that it’s a misconception. But, technically speaking, we do not have the right “gear” to directly sense wetness – even though we all know when something is wet.
But how does that work?
Why humans can’t feel wet
Humans lack dedicated hydroreceptors – the specialized sensory receptors solely responsible for detecting wetness. As a result, wetness is not a distinct sensation for us, but rather an interpretation of multiple sensory inputs.
When a liquid, such as water, comes into contact with the skin, several different types of sensory receptors are activated. These include thermoreceptors, mechanoreceptors, and nociceptors. Thermoreceptors respond to temperature changes and can detect the cooling effect of the liquid on the skin. However, this response alone does not convey the specific quality of wetness.
Mechanoreceptors, responsible for sensing pressure and touch, provide information about the physical presence of the liquid. They detect the pressure exerted by the liquid and signal the brain accordingly. However, the activation of mechanoreceptors alone does not differentiate between wet and dry sensations.
Nociceptors, which detect pain and discomfort, may also play a role in the perception of wetness. If the liquid is extremely hot, cold, or otherwise causes discomfort, nociceptors are activated, contributing to the overall sensation. However, this response is not exclusive to wetness and can be triggered by other stimuli as well.
How we sense “wet”
Due to the absence of dedicated hydroreceptors, the brain must integrate and interpret these various signals to create the perception of wetness. It combines the inputs from thermoreceptors, mechanoreceptors, and nociceptors, along with other contextual cues, to generate the subjective experience of being wet.
While humans can recognize and differentiate wet sensations, it is important to note that wetness itself is not a distinct sensory modality. Rather, it is a perception resulting from the brain’s processing of multiple sensory inputs related to temperature, pressure, and even discomfort.