This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: It's a cold winter afternoon, and you've just brought the laundry in. Are these clothes a bit damp?
In the laundry basket, your hand can clearly distinguish the textures of silky shirts, woolen sweaters and cotton bedsheets. So why is it so hard to tell whether the laundry is cold and damp or just cold? A sensible guess might be that our hands are numb from the cold, making it harder to detect wetness.
The less intuitive reality is that humans completely lack specialized sensors that respond to "wetness" in the first place. That's right—your skin alone can't actually detect whether something is damp. Our ability to sense information about our external environment starts at nerve cell endings in our skin.
There are specialized molecules on the surface of these nerve cells called sensory receptors. They convert environmental information into a biological signal, which is amplified into an electrical impulse and transmitted along nerve cells to the brain. There are numerous sensory receptors in nerve cells that are activated by cold, warmth or damaging heat.
There are also sensory receptors that respond to precise tactile information, such as vibration, friction or stretch. When you put your hand in that laundry basket, all the information about temperature and texture comes from the relevant sensory receptors in your hand. The electrical signals triggered by these multiple inputs can also be integrated in the central nervous system, including the brain.
In this way, we can infer an extraordinarily nuanced sense of our environment. Our experience of wetness arises in this way. It comes from the combined input of cold and friction receptors, refined by association with previous experience.
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