Tactile communication: how touch conveys the things we can’t say
By Lily McCann
Our daily dose of touch has decreased through months of lockdowns. But why is touch so important to us, and why do we feel the lack of it so severely?
Edited by Juulke Castelijn and Ethan Newnham
December 10, 2021
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Illustration by Janna Dingle
In a confusing world, thrust in and out of lockdowns, estranged from family and friends, you may have felt somewhat lost and out of touch in recent years. What helps to bring you back to a sense of self and belonging? For me it's a hug from my partner, a pat on the back from a sibling or a cuddle with my dog. Positive physical contact helps ground us and reassure us of our place in the world.
It's an instinct cultivated from our first moments of life and one crucial to development. As the first sense to form, touch is the start of our gradual awakening into the world and informs our developmental progress. Even touching a mother’s stomach in pregnancy can alter the behaviour of the foetus within[1].
In the mid-late 20th century, researchers began to study the impact of sensory deprivation on children and infants, examining those placed in institutions who suffered from neglect[2]. This was a poignant problem following World War II, when millions of children were orphaned or displaced. The limited number of carers in overcrowded orphanages that attempted to harbour them meant that infants and young children were often left to lie day after day without a hug, stroke or any other form of caring contact. Upon studying these children, it became clear that the impact of deprivation was devastating, resulting in a number of cognitive, behavioural and physical deficits. Studies have since established that increasing tactile contact with developing children is protective against such problems[3]. For instance, simply stroking isolated premature babies improves mental development and physical growth[4].
It seems that touch provides a message to the infant’s body, communicating that it is safe and guarded and in an environment where it can grow and flourish. As you might expect, this process is closely related to stress responses. Studies have shown that in stressful situations of food deprivation, mice populations prioritise survival, neglecting breeding and exploration. When food is plentiful, this is reversed. A mother’s touch has a similar effect on human infants, decreasing stress levels and facilitating development and exploration[5].
We see another good example of this in dogs. Along with other domesticated animals, dog display something called ‘Domestication Syndrome’, which describes a set of features animals shaped by human breeding efforts share[6]. The ‘cute’ physique of such animals (floppy ears, snubby nose, curly tails) are correlated with increased stress tolerance and more tame behaviours. Interestingly, in dogs this decrease in stress is also paired with increased desire for and pleasure in touch. This is clear even between dog breeds: the working Australian Kelpie with its active herding instincts is more likely to chase down a bicycle than snuggle into you and ignore it like the floppy-eared Cavalier.
Correlation studies abound, but what about the mechanism behind all these associations? How does touch affect our body? How is its message conveyed?
The key mediators of tactile communication are nerve cells, otherwise known as neurons. These cells conduct signals to, from and within our brain. They’re particularly important for sensation, transferring information about our external environment to our inner mind. For touch, there are neurons in our skin with specialised endings that can sense pressure,
vibration, temperature and stretch. They respond to these stimuli by firing little signals that tell our brain we’re touching something.
There are actually two distinct types of touch that we use. Typing, turning book pages or handling tools are all mediated by the first type, discriminative touch, which is mainly limited to the palmar surface of our hands and fingers. Have a look at your palm now, then flip it over and examine the back of your hand. Notice anything different?
The main difference is that the inner surface of your hand is smooth. Check out the back of it – it’s hairy. Hairy skin is differentiated by – you guessed it – hair, but also by the method of touch sensation. The type of touch experienced by hairy skin is affective touch.
Affective touch holds the key to explaining our emotional dependence on tactile communication because it describes touch that has emotional and social relevance. It relies on a type of sensory nerve called CT fibres, which are specialised for positive social touch: they respond best to the temperature of human skin and a gentle, stroking pressure. Parents automatically use this sort of touch when interacting with their children[7].
This caring touch is incredibly powerful. It can cause the release of oxytocin (the “bonding hormone”)[8], decrease stress levels[9], and trigger the facial muscles that form a smile[10]. It can stimulate unique emotional responses, such as excitement, affection or calm. It even has the power to speak to DNA itself: research has shown that changing touch exposure in mice affects how DNA is structured and expressed[11].
Social touch is an essential component of how we define ourselves as humans. Without it, touch would mean nothing more than that a person is present, that their skin is warm or cold, dry or wet. The warmth of our partner’s hand wouldn’t create a sense of belonging, hugging a friend wouldn’t trigger memories of time spent together, stroking your child wouldn’t give rise to feelings of love. Affective touch colours our world and gives it meaning.
Whilst some suggest that social touch encompasses all intentional, consensual interpersonal touch, I would argue that even accidental touch has a social impact[12]. In recent times we have all felt the change of walking down empty streets. Where bumping or brushing against another person was taken for granted as simply unavoidable on the morning train a couple of years ago, COVID19 has introduced new connotations to such accidental touch, all but prohibiting it. Whilst you may have been frustrated by clustered train carriages, you can’t help but notice that it feels a little lonely when the train is quiet, and the nearest passenger is more than 1.5m away. Even accidental touch signals to the body that you are part of a community, part of a herd, and for a social animal that must be comforting. Look at sheep, for instance: under stress, harassed by sheepdogs or farmers, they automatically cluster together in a group. Whilst an individual bump between two sheep in the herd may be fortuitous, the fact that crowding together maximises interpersonal contact is no accident.
The comfort of touch is a fact of human life, but one not often actively acknowledged. Lockdowns and isolation have reminded us all how necessary social contact can be for our wellbeing. Touch is a part of the chatter that defines our place amongst others and our identities as part of a community. So if your pet, friend or partner are in need of comfort, administer a bit of affective touch and see the miraculous calming effects of the actions of those CT nerve cells. Stay safe and sanitise, but remember, hugs are helpful too!
REFERENCES
[1]Marx, Viola, and Emese Nagy. 2017. "Fetal Behavioral Responses To The Touch Of The Mother’S Abdomen: A Frame-By-Frame Analysis". Infant Behavior And Development 47: 83-91. doi:10.1016/j.infbeh.2017.03.005.
[2] van der Horst, Frank C. P., and René van der Veer. 2008. "Loneliness In Infancy: Harry Harlow, John Bowlby And Issues Of Separation". Integrative Psychological And Behavioral Science 42 (4): 325-335. doi:10.1007/s12124-008-9071-x.
[3] Ardiel, Evan L, and Catharine H Rankin. 2010. "The Importance Of Touch In Development". Paediatrics & Child Health 15 (3): 153-156. doi:10.1093/pch/15.3.153.
[4] Rice, Ruth D. 1977. "Neurophysiological Development In Premature Infants Following Stimulation.". Developmental Psychology 13 (1): 69-76. doi:10.1037/0012-1649.13.1.69.
[5] Caldji, Christian, Josie Diorio, and Michael J Meaney. 2000. "Variations In Maternal Care In Infancy Regulate The Development Of Stress Reactivity". Biological Psychiatry 48 (12): 1164-1174. doi:10.1016/s0006-3223(00)01084-2.
[6] Trut, Lyudmila. 1999. "Early Canid Domestication: The Farm-Fox Experiment". American Scientist 87 (2): 160. doi:10.1511/1999.2.160.
[7]Croy, Ilona, Edda Drechsler, Paul Hamilton, Thomas Hummel, and Håkan Olausson. 2016. "Olfactory Modulation Of Affective Touch Processing — A Neurophysiological Investigation". Neuroimage 135: 135-141. doi:10.1016/j.neuroimage.2016.04.046.v
[8]Walker, Susannah C., Paula D. Trotter, William T. Swaney, Andrew Marshall, and Francis P. Mcglone. 2017. "C-Tactile Afferents: Cutaneous Mediators Of Oxytocin Release During Affiliative Tactile Interactions?". Neuropeptides 64: 27-38. doi:10.1016/j.npep.2017.01.001.
[9]Field, Tiffany. 2010. "Touch For Socioemotional And Physical Well-Being: A Review". Developmental Review 30 (4): 367-383. doi:10.1016/j.dr.2011.01.001.
[10]Pawling, Ralph, Peter R. Cannon, Francis P. McGlone, and Susannah C. Walker. 2017. "C-Tactile Afferent Stimulating Touch Carries A Positive Affective Value". PLOS ONE 12 (3): e0173457. doi:10.1371/journal.pone.0173457.
[11]Bagot, R. C., T.-Y. Zhang, X. Wen, T. T. T. Nguyen, H.-B. Nguyen, J. Diorio, T. P. Wong, and M. J. Meaney. 2012. "Variations In Postnatal Maternal Care And The Epigenetic Regulation Of Metabotropic Glutamate Receptor 1 Expression And Hippocampal Function In The Rat". Proceedings Of The National Academy Of Sciences 109 (Supplement_2): 17200-17207. doi:10.1073/pnas.1204599109.
[12] Cascio, Carissa J., David Moore, and Francis McGlone. 2019. "Social Touch And Human Development". Developmental Cognitive Neuroscience 35: 5-11. doi:10.1016/j.dcn.2018.04.009.