science

With the exception of a small few, we’ve all felt the instant Zen that comes from a carefully given caress. That feeling of absolute calm and safety. Turns out, this is as much a fascinating feat of biology as it is an endearing perk of being alive.

As explained by Cambridge Professor and Science Communicator Hannah Fry in a now-viral Instagram video, humans are hardwired with a variety of different touch triggers, aka neurons, that respond to different stimuli. Some react to hot, some react to cold, some react to pain, and so on.

C-tactile (CT) afferents are neurons that only react to a very particular kind of touch. Go too fast, too slow, or too cold (below around 32°C/90°F), and they won’t respond at all. But when someone else (key ingredient here) gently brushes your skin at the optimal speed (about three centimeters per second) your brain releases endorphins and oxytocin, chemicals associated with trust and connection. In other words, it sets off your body’s built-in calming mechanism.

“You have a literal switch in your skin that is pre-programmed to make you feel safe. But you have to get somebody else to flip it,” as Fry put it. Do we need more evidence that humans are hardwired for connection with each other? Of course, humans aren’t the only ones with this mechanism. It’s the same reason why our fur babies lean in when we pet them just right.

What’s more, Fry noted that this ultra-specific type of touch is something that mothers tend to know instinctively. In her video, she cited a 2022 study that found when mothers applied it to their preterm infants, which they did without any prompting, it caused the babies’ heart rates to drop and stress levels to decrease. Earlier studies showed similar results: better oxygen levels, calmer babies, and even shorter hospital stays.

While CT afferents aren’t a new discovery, Fry’s explanation struck a chord because it translates complex biology into something wonderfully human: a “biological lullaby.”

“Biological lullaby’ is such a beautiful and descriptive word combo,” wrote one viewer.

Many noted how this heartwarming phenomenon is something universally known amongst more than just mothers.

“As a father of two girls and a granddaughter I know this instinct,” another argued. “The pleasure of this act is equally beneficial to us as parents. It takes me back 🙏true love ❤️”

Similarly, another shared, “Can confirm dads can do this too. Two dads here, our twin girls were premature at 35 weeks. We pretty much spent every single minute that we weren’t asleep with them in the NICU, skin on skin etc.. but I do remember both of us just randomly going in a rhythm of this perfectly medium tempo gentle stroking.”

Even a hospice nurse wrote, “I do this with all my patients. As soon as I smooth their hair back that way they just melt. Many haven’t felt that since they were very young. It has tremendous impact on people at the end of life. It’s truly transformative. Ending their lives the way they began, with nurturing touch.”

How to use CT-touch in daily life

Even though we do have an instinct for this special touch, you can get it down to a science simply by incorporating calm, slow strokes on a loved one’s arm, back, or chest (making sure your hands aren’t too cold!). This can be great to have in the back of your mind when a baby starts to get fussy, or even when our fully grown partner is having a moment. There of course is the caveat that touching might not elicit the same feel good chemicals for some folks. Those who are neurodivergent or have PTSD, for example, might prefer to avoid it. A lot of different factors can alter our perception of touch as we grow up.

In an age when much of our comfort comes from screens, Fry’s viral insight feels refreshingly simple: our nervous systems are built for closeness. Touch is one of the oldest forms of communication we have, and it still works. Incredibly well, at that. What a profound reminder that perhaps our most primal urge of all is to be reassured that we are never truly alone.