Why Hugs Strengthen Friendships — the Science Behind It

Why Do Hugs Strengthen Friendships?

Physical touch activates a highly specialized system of afferent nerve fibers — the C-tactile (CT) nerves. These fibers directly trigger β-endorphin release, creating feelings of warmth, calm, trust, and connectedness (Dunbar, 2025).

Keverne et al. (1989) demonstrated the connection experimentally: monkeys given morphine lost interest in grooming. When given naloxone (an opioid antagonist), they demanded it constantly. The brain actively seeks the endorphin release that touch provides.

C-Tactile Nerves: The Touch Channel

CT nerves are remarkable in several ways (Olausson et al., 2008). They are unmyelinated (slow transmission rates), have no motor feedback loop, and project to the insula — a brain region for emotional processing — rather than to the somatosensory cortex, where most other peripheral nerves target.

Most strikingly, they show extreme stimulus specificity: they respond exclusively to light, slow stroking at about 3 cm per second — precisely the speed of hand movements during social grooming. At 1 cm/s or 30 cm/s, nothing happens. Activation is strictly limited to this speed.

Suvilehto et al. (2015, 2019) also showed that the topography of social touch depends on emotional closeness and is remarkably similar across cultures. The closer the relationship, the larger the accepted area of touch.

Humans vs. Primates: Mutual Touch

Humans have a decisive advantage over other primates: the ability for simultaneous touch. While grooming in apes is normally unidirectional — one animal grooms while the other often falls asleep — humans can touch each other at the same time.

This doubles the endorphin effect. That is why a hug is so powerful: both sides touch and are touched — simultaneously. Yet touch remains a strictly dyadic activity, limited to a maximum of about 50 people. That is why humans have developed additional bonding activities such as laughing, singing, and dancing — mechanisms that release endorphins without body contact and scale to larger groups.

Limits of Touch

The extreme specificity (only 3 cm/s) was measured mainly under laboratory conditions. Whether natural social touching actually maintains this speed consistently is less clear. Cultural norms regarding physical touch also vary considerably.

In low-touch cultures, alternative bonding activities play a proportionally larger role. And for in-person meetings, this holds: even without body contact, they activate endorphins through laughter and conversation. Touch is the most efficient path, but not the only one.

Frequently Asked Questions

Why do hugs feel good?

Because of C-tactile nerves — specialized, unmyelinated nerve fibers that respond exclusively to light, slow stroking at about 3 cm per second. They project to the insula (not the somatosensory cortex) and directly trigger β-endorphin release.

How does touch strengthen friendships?

Through the endorphin mechanism: C-tactile nerves activate β-endorphins, which create feelings of warmth, trust, and connectedness. This mechanism is the evolutionarily oldest and most direct way to strengthen friendship bonds.

What are C-tactile nerves?

Specialized afferent nerve fibers that respond only to a specific touch speed (~3 cm/s). At 1 cm/s or 30 cm/s, nothing happens. They are unmyelinated, slow, and target the insula — a brain region for emotional processing.

Can you have close friends without physical touch?

Yes. Humans have developed alternative mechanisms: laughing, singing, dancing, and group sports activate the endorphin system without body contact. But touch remains the most efficient trigger — and the only one where humans can double the effect (simultaneous touching).