From all senses that we develop, touch is the first one to form. During pregnancy, fetuses will begin developing feelings of sensations on their faces at week 8. Yet, the nose and the lips will be responsible for processing nearly all sensations. A month later, feelings on the palms and soles will develop, and if we wait for an additional five weeks (week 17), the abdomen will start sensing too. Interestingly, our brain will devote a majority of its attention to those parts especially. It is relatively easy to test this. Try prodding someone else’s back, with their consent, and ask them to evaluate how far two prods are from each other. Then do the same again, but this time over their palm. Were the results similar? Hopefully, the palms results should be unquestionably more accurate than the back results. This effect is possible through the bulkier number of neuronal endings found on the skin of our palms compared to those on our back.
Speaking of neuronal endings, we cannot avoid talking about the many specialized sensory neurons that form the somatosensory neural pathways, which get completed by the middle of the third trimester. From this point on, the baby will feel a more integral range of feelings. Each specialized sensory neuron has, on its endings, receptors that are enabling the perception of different sensations. Mechanoreceptors will provide detection for pressure, light touch, tearing or vibration. Thermoreceptors are sensitive to temperature changes. Chemoreceptors will detect chemical changes, and nociceptors are responsible for transmitting pain signals. It is intriguing to note that pain is the last sensation to develop and appear through the formation of totally different pathways (read https://bringupscience.com/2021/01/23/bring-up-pain-2/ for more). In sum, all specific tactile inputs have distinct neurons responsible for their detections. This statement also applies to touch in social interactions. As opposed to ordinary touch, the tap that we receive on the back of our shoulder, as praise, elicits an emotional response. This particular tactile sensation makes up what we now describe as social or emotional touch. It recruits a different somatosensory system than the one involved in conventional touch.
A piece of evidence supporting the idea that social touch involves the activation of different pathways comes from studying people affected by primary sensory neuropathy. Individuals affected by this disorder are known to display touch blindness, i.e. they cannot feel any tactile input coming from neither their hands nor their bodies. They are even incapable of reading braille, where each letter corresponds to a dot pattern, and all dots are embossed. This adaptation, commonly, grants people who cannot read solely based on their sight the ability to read through touch. Thus as already mentioned, individuals affected by this neuropathy cannot read, nor can they feel the object coming in contact with their skin. However, they strangely can feel a touch from another person and attribute it an emotional value. They, indeed, can feel the gentle touch of someone stroking their arm and communicate that the touch felt pleasant. However, this theory is currently based on anecdotal evidence only, and thus we shouldn’t jump to any conclusion just yet.
Even if social touch turns out to have no different pathways than conventional touch, it would be reasonable to keep in mind the importance of its impact anyway. Indeed, some orphan children, who grew up in an orphanage, received so little social-emotional interaction that it hampered their growth dramatically and, in some instances, even led to death. I should disclose that customarily the orphanage staff was conveying proper treatments with absolutely no intention of neglect. Unfortunately, they were often too few and could honestly not care for more than the children’s most basic needs. Those needs were thought, at that moment, to be strictly drinking, feeding, sleeping and occasional physical activity. As long as these aspects were all taken care of, they genuinely believe that they tended well. Only now we know that social touch is amongst those basic needs. The lack of it will downright kill a kid. Current studies have demonstrated that social touch enables growth hormone release and will stimulate the immune system. Researchers have found similar findings to support the reciprocal, i.e. that a lack of social touch hinders growth hormone release and cripples the immune system. Moreover, children who were unfortunate enough to have been placed in such an institution were found at an elevated risk to develop behavioural, social and psychological problems.
Additionally, social touch occupies such a meaningful place in our life that, as a result, we may mistakenly associate general tactile inputs to our impression of a person. To illustrate this idea, let us consider this well-known experiment conducted by social psychologists. The psychologist asked the volunteers to describe their first impressions of a stranger. Every subject of the study had the same task, to relay their general impression. The only difference between all the volunteers was the drink they were holding while meeting this other person: Half held a cold drink and the rest a hot drink. We would all think that the beverages they were holding should have no impact on their impression of another individual, but that is not what happened. Curiously, people holding the hot drinks described their new acquaintance as “warmer”; the inverse was also true for the cold drink volunteers. Another experiment tried a different approach through evaluation of the same resume but on two differently weighed clipboards. It seemed that the resume attached to the heavier clipboard made the candidate seem more serious and competent than the individual whose resume was attached to the lighter clipboard.
Despite social touch playing an integral role in our life, it is not the only factor that can interfere with our touch perception. Emotions play a considerable role in how we interpret touch or pain. The feeling we bear in a particular moment (good/bad mood, relaxed/scared, rested/tired, etc.) may considerably impact how we will perceive that tap on our back. The same tap may feel like an assault or an encouragement, depending on your emotion at the time. If you hate the person, you might think of that tap as an assault, but if that person is a friend, then you could have perceived it as an encouragement. Additionally, when we feel happy, pain does not seem as terrible as when we are sad or depressed. We can only say that touch and emotions are in a very intricate relationship, indeed.
Now, I cannot write about touch without talking about tickles. I honestly find them somewhat intriguing since no one has yet to come with an irrefutable explanation as to why we feel them. There are many theories, however. My favourite one introduces tickles as an evolutionary mechanism that leads to more capable offspring. Tickles are, in the simplest terms, the results of neuronal overexcitation. We, as adults, can feel tickles in only our most sensitive areas, but as a kid, that surface can be as great as the entire space occupied by your skin. Sadly, our sensitivity, as we are ageing, seems to decline progressively. The duality of tickles (being felt as both unpleasant and pleasant) supposedly serves as both an incentive to protect the sensitive areas and encourage wrestling and fighting. Those two consequences force offspring to prepare and practise both their offensive and defensive strategies to better cope with inevitable future threats. It seems such a no-brainer that the more you practise, the better you become, and this is why I genuinely value this idea.
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