Your Skin Has No Sensor for Wetness
The feeling is made in the brain from temperature and touch.
youtube.com · Lisa Feldman Barrett: Love, Evolution, and the Human Brain | Lex Fridman Podcast #140
Skin has no water receptors for wetness, a fact that surprised Lisa Feldman Barrett, a neuroscientist at Northeastern University.
She said that was her reaction too, and agreed it made sense because humans evolved in water, so there was no need for a separate wetness sensor.
Instead, she explained, wetness is a complex sense computed only in the brain from temperature, touch, and how big the drop is. That combination is why snow, cold rain, and warm rain feel different from one another.
Questions people ask
If I cannot sense water, how do I know when I am sweating?
The general explanation outside this interview is that sweat cools the skin as it evaporates and changes how skin and clothing feel to the touch. The brain combines that cooling and touch to produce the feeling of dampness. That is why a humid day can feel clammy even before sweat drips.
What sensors is the brain using instead?
Temperature is reported by thermoreceptors in the skin, and contact and movement are reported by touch receptors. The brain combines those separate streams to form wetness. There is no third stream for water itself.