Can humans feel wetness? It may sound like a strange question, given that you definitely feel like you can tell when an object is wet, but there is a bit of reasoning behind it.
Twitter user @HannahPosted recently informed her followers that humans do not have a direct way to detect wetness, relying instead on other senses.
The idea likely comes from a 2014 study, or a number of studies since, looking into human wetness perception.
“In contrast with insects, in which humidity receptors (i.e., hygroreceptors) sub-serving humidity detection (i.e. hygrosensation) have been identified and widely described,” one team wrote in 2015. “Humans’ largest sensory organ, i.e., the skin, seems not to be provided with specific receptors for the sensation of humidity and skin wetness.”
As explained, humans do not have specific hydroreceptors. Instead, we appear to rely on a mixture of inputs, as one team found out in 2014 by placing various stimulus onto volunteers’ hands and arms. As the temperature of objects they were in contact with decreased, for example, their sense of wetness increased, indicating that temperature played a part in how we perceive it. They also found that hairy skin is more sensitive to wetness than non-hairy skin, and that wetness sensation was dulled when nerves were blocked using an inflatable blood pressure cuff.
“Wetness is one of the most common sensations we experience, so people don’t question it. You can trick your brain to feel wet when something is not wet, or trick it to feel dry when in fact something is wet,” first author of the study, Dr Davide Filingeri, told Re:action magazine in 2021. “If you are sitting on a metal chair with bare skin, you might jump up feeling wet when really it’s just the cold of the metal that cools the skin very quickly. Or, if you wear a latex glove and put your hand into water and take it out again, you will probably feel wet on your hand even though there is no moisture in contact with your skin.”
“Given noisy and ambiguous sensory inputs (such as thermal and mechanical stimuli on the skin), the brain is thought to estimate which events caused these inputs (e.g., the presence or absence of physical wetness on the skin), on the basis of prior knowledge that is acquired and shaped by sensory experience,” the team wrote in their study.
“The outcomes of this study have indeed indicated that in order to sense cutaneous wetness a multimodal integration of thermal (i.e., cold) and mechanical sensory inputs had to take place,” they explained. “From a functional point of view, this was confirmed by the fact that when the activity of A-nerve fibers was selectively reduced the extent of perceived wetness was also significantly reduced. From a central processing point of view, this was confirmed by the fact that, although all the stimuli had the same moisture levels, warm-wet and neutral-wet stimuli were sensed as significantly less wet than the cold-wet stimulus.”
So that’s settled, in the most pedantic sense possible, humans can’t feel wetness, and can only infer wetness from other sensory inputs. We will never know true wetness, until we finally find a way to fuse our kind with insects.
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Source Link: Humans Technically Can't Feel Wetness, And People Are Confused