How do we know when something is wet? © Getty Images

How do we know when something is wet?

Wetness is a property that our nervous system learns to recognise, based on a mixture of cold, pressure and texture.

Asked by: Peter Fraser, London

Advertisement

Our skin contains lots of nerve endings that respond to different stimuli. There are receptors for touch, vibration, heat, cold and pain – but not for wetness. Water is such a ubiquitous component of all living cells that it would be difficult for a nerve cell to avoid firing constantly in response to its own composition.

Instead, wetness seems to be a property that our nervous system learns to recognise, based on a mixture of cold, pressure and texture. A 2014 study at Loughborough University found that hairy skin is more sensitive to wetness than smooth skin, which may be because hairy skin has more temperature-sensitive nerve endings. When you are born, you don’t feel wet or dry, you just feel cold or warm. Over time we learn that the feeling of cold cloth sticking to our skin means that we’ve sat on a wet park bench.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.