Consoling touch

The importance of consoling touch was first explored by Harry Frederick Harlow (Oct 31, 1905 – Dec 6, 1981). From 1950 through 1970, Harlow conducted controversial research on rhesus monkeys observing maladaptation resulting from maternal-separation and social isolation.[12] Infant monkeys were separated from their biological mothers and given two inanimate surrogate mothers. Cheekily referred to as ‘Iron Maidens’, the first of the two surrogates was constructed of wire and contained a feeding mechanism. The second contained no food and was constructed of rubber and soft terrycloth. In all variations of the paradigm the infants spent significantly more time clinging to the cloth mother. Only when the monkeys were hungry did they leave the terrycloth, only to return to it after eating. Monkeys accompanied by iron maidens behaved differently in novel environments than those in complete isolation. When chaperoned by a surrogate mother monkeys explored new environments, retreated to the surrogate when startled, only to continue exploring thereafter. Monkeys put in novel environments without an iron maiden cowered in the nearest corner, too fearful to explore. Those raised in complete isolation developed marked disturbed behavior such as pacing in cages, staring blankly, and self-mutilation. When introduced to other rhesus's, those raised in isolation did not socialize, kept separate from the group, and refused to eat. Harlow rehabilitated socially inept monkeys by enclosing them with a non-threatening, well socialized other. Harlow observed these social pair interactions, calling them "the isolate and the therapist'. Upon introduction, the isolate huddled in a corner. The therapist reacted by embracing the isolate. With consoling touch and modeling of social interaction, isolates were indistinguishable from therapists after one year. Harlow concluded that social rehabilitation is possible, however there may be a critical period, much like language development in humans. The need for close comforting physical contact became known as contact comfort.[13][14] Contact comfort is believed to be the foundation of attachment and serves as the basis for consoling touch.

Extensive research has documented the importance of physical touch in human emotional and physical wellbeing. From a developmental perspective touch plays a vital role in infants’ physical and cortical growth, stress relief, and secure attachment formation.[15][16] Nurturing touch is positively associated with children's neuronal development thus determining the trajectory of their behavioral and cognitive growth.[17][18][19] Though no laboratory studies exist due to ethical considerations, data emphasizing the necessity of consoling touch was taken from orphanages where the caretaker to child ratio was 1:25. Children deficient in consoling touch during critical developmental stages had between 20%-30% less brain mass than children of similar age who received sufficient socialization.[20] In a 1997 study, Dawson et al. monitored the neural functioning of children born to depressed mothers. A key symptom of maternal depression is reduced social touch between mother and child. The electroencephalogram (EEG) results of children with depressed mothers had markedly reduced activity in the left frontal lobe. The abnormality remained consistent with the mother's condition throughout the duration of the three-year study. The children of mothers who managed to diminish depressive symptoms before their child's first year later developed a more normal brain pattern.[21] The likelihood of full neural recovery lessens as a child ages due to sensitive periods for brain development, the first year and a half being the most critical.[22]

Consoling touch has an emotional component that utilizes different neural networks and nerves than physical sensation processing alone.[31] This distinction has been described by studies examining discriminative touch versus affective touch. Discriminative touch conveys information regarding pressure, vibration, or stretching of the skin. This kind of processing involves type A nerve fibers, which relay information very quickly to the brains sensory regions. Affective touch, however, involves type C nerve fibers. Unmyelinated, slower traveling, type C nerves communicate pain signals, temperature, and social touch.[38][39] In humans, type C nerves have the greatest response to soft strokes from stimuli matching skin temperature.[40] These afferent nerves also exhibit a tuning curve for caressing speed specific to that which an individual finds most pleasant. The 'social touch hypothesis', coined by Håkan Olausson in 2010, proposes that C afferent nerve fibers are most sensitive to tactile stimuli occurring during close social interaction.[39]

Individuals vary in their preference for consoling touch. It is speculated that culture and upbringing are the greatest determinants.[48] Going beyond environmental factors, there is a notable relationship between tactile experience and the autism spectrum. 96% of individuals on the spectrum report an altered, and largely heightened, sensitivity to tactile input.[49] These variations in nerve processing manifest in different ways, be it wearing very specific fabrics, or avoiding rain because the sensation of drops on the skin is painful.[50] Kevin Pelphrey, a clinical neuroscientist at Yale, recently evaluated response to social touch in neurotypical and neurodivergent children. Children had their arms gently grazed with a paint brush and had their palms touched by a caregiver while in an fMRI scanner. Neurotypical children elicited the expected response. There was heightened activation of C afferent nerves and the posterior insula in the palm touch condition while type A nerves responded to the paintbrush condition. The children on the Autism spectrum, however, elicited a similar neuronal response in both conditions with marked activation of the somatosensory cortex.[48] The findings raise the possibility that individuals on the spectrum may not be extracting social information from touch.[49] These findings are preliminary and cannot be used to assume individual preference or experience of social touch.

• Affective haptics
• Social rejection