Touch may seem simple, but is actually quite complex. The human brain is capable of differentiating sensations (a pin prick vs. an itch), temperature, pressure, and even emotional intention. Touch is critical in that it allows us to navigate worlds both physical and social. Affective, culture-based information is conveyed through touch. Today we’re considering how pleasant, non-sexual affective touch affects learning and development across the human lifespan.
First, let’s define social, affective touch. According to a recent article in Developmental Cognitive Neuroscience, This type of touch is distinguished by special nerve fibers, called C fibers, C-touch fibers, or CT fibers. These unmyelinated, thin nerve fibers are responsible for detecting gentle strokes at body temperature. The recipient identifies affective touch as pleasant; it spurs the release of the social bonding hormone oxytocin. Some researchers have called the CT afferents “the social touch system,” as these fibers seem to be responsible for social rewards.
A final distinguishing characteristic is that CT fibers connect to the brain’s posterior insular cortex, rather than the primary somatosensory cortex, where fibers for tactile manipulation and discriminative touch project. The brain processes affective touch through two pathways: the neural circuits for emotional information, and other conduits for interoception, or awareness of what is happening within one’s body. This neural mapping points to the developmental importance of receiving affective touch.
Touch: Key for Human Development
Touch is the first sense to develop; babies use it to understand their own bodies. At first, touch establishes a sense of self. The lessons of touch begin in utero; fetuses work on mapping their bodies through movement and self-touch in the womb. Let’s consider how touch continues to influence development across a human life.
- Social Reward
Researchers believe that affective touch helps infants and children create healthy neural reward systems. Parents who deliver pleasant touch are teaching their children to respond to social reward systems. Positive touch received within a nuclear family correlates with sustained positive emotions.
Researchers have called touch a “key ingredient” in developing secure parental attachment, as well as familial bonds. Secure attachment is associated with social confidence, empathy, and cooperation later in life.
Early communication between baby and parents is often accompanied by touch. While teaching basic vocabulary, parents often include a gentle touch. This has been found to improve children’s understanding of parent communication. Finally, touch can be a way for children to communicate their feelings with caregivers, even in children as young as five months old.
- Emotional Regulation
Animal studies suggest that increased social touch during infancy leads to improved resilience. For instance, in a study involving prairie voles, low-touch mothering was found to produce more aggressive pups. Maternal licking and grooming in the first week of life was found to reduce stress reactivity while increasing cognitive ability and exploratory behavior. While human studies are less common, we do know that babies exhibit more engagement and a lower heart rate while receiving pleasant, CT-targeted touch.
As children leave home for school, they receive more benefits from positive touch. Positive touch from teachers is associated with fewer classroom disruptions and more on-task behavior. This list is just an introduction to the myriad benefits of social touch, which also leads to improved infant weight gain, shorter hospital stays, stronger neural responses, and even increased oxytocin in parents!
How Lack of Touch Impacts Development
Given the importance of affective touch in social development, you might anticipate social difficulty when healthy touch is restricted or absent. Researchers have found the following negative consequences for lack of touch:
- Higher risk for sensory processing disorders, such as oversensitivity
- Increased likelihood of autism spectrum disorder
- Impaired growth and cognitive development
- Decreased scores on motor assessment tests.
Again, animal studies can provide more information. An early touch study, published by Hammett in 1922, found infrequently handled rats to be more “timid, apprehensive, and high strung” than their peers who received increased touch. Isolated, touch-deprived rats were also found to be less attentive to offspring. Another study found that rats who receive less touch experience attention difficulties later in life.
As discussed in Psychology Today, loving touch empowers the brain to “construct a sense of body ownership” while also “creating a healthy sense of self.” Researchers now believe that all animals, including humans, need touch for proper development. As Ardiel and Rankin conclude, “Organisms need sensory stimulation for normal development.”
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- Ardiel EL, Rankin CH. The Importance of Touch in Development. Paediatrics Child Health. 2010 Mar; 15(3): 153-156.
Cascio CJ, Moore D, McGlone F. Social Touch and Human Development. Developmental Cognitive Neuroscience. 2018 Apr. https://doi.org/10.1016/j.dcn.2018.04.009