7 Activities That Are Proven to Strengthen Friendships

Why Do Certain Activities Strengthen Friendships?

The answer lies in the endorphin system. In primates, social bonding is primarily built through mutual grooming — it releases β-endorphins that bind to μ-opioid receptors and produce a feeling of warmth and connectedness. In humans, social groups extend far beyond the capacity for one-on-one grooming.

The solution: humans evolved activities that release endorphins in multiple people simultaneously. Manninen et al. (2017) confirmed via PET scan: shared laughter activates the μ-opioid receptors in the brain. The naltrexone blockade (Tarr et al., 2017) confirmed the causal role: when the opioid system is blocked, the social bonding effect disappears.

The 7 Activities

Dunbar (2025) summarizes the social toolbox:

1. Laughing— one of the most effective ways to release endorphins without physical contact. Shared laughter and humor significantly increase pain tolerance.
2. Singing— creates strong group bonding, even among strangers. Choir rehearsals lead to feelings of connectedness faster than other group activities.
3. Dancing— combines movement, rhythm, and synchronization. Endorphin release is especially high when movements are synchronized.
4. Team sports— increase pain tolerance as an endorphin marker. Physical activity in a team is more effective than exercising alone.
5. Eating together— activates the endorphin system through sensory experience and the shared ritual. Commensality (shared meals) is one of the oldest bonding practices.
6. Emotional storytelling— sharing personal stories generates empathy and activates the opioid system through emotional resonance.
7. Religious rituals— combine singing, dancing, synchronization, and emotional experience into a particularly potent bonding cocktail.

Synchronization Amplifies the Effect

Tarr et al. (2017) showed experimentally: synchronous dancing significantly increased pain tolerance (an endorphin marker) and perceived connectedness more than asynchronous dancing. Rowing in rhythm together produces a stronger effect than the same workout alone.

The mechanism: synchronization requires attention to the other person. The brain must coordinate its own movements with those of the counterpart — a form of physical empathy that signals connectedness beyond the endorphin effect.

Only Those Present Benefit

An important caveat: the endorphin system is primarily activated through physical presence. Laughing together over a video call, singing along digitally — these can maintain friendships but do not produce the same neurochemical effect as a physical encounter.

This explains why physical closeness remains so central to friendships: only those who are physically present benefit from the biochemical bonding effect. This is not nostalgia — it is neurobiology.

Frequently Asked Questions

Which activities strengthen friendships?

Seven activities form the “social toolbox” (Dunbar, 2025): laughing, singing, dancing, team sports, eating together, emotional storytelling, and religious rituals. All of them activate the μ-opioid system and release endorphins that biochemically reinforce social bonding.

Why is team sport more effective than exercising alone?

Synchronized activities — such as rowing in rhythm together — produce a stronger endorphin effect than the same activity performed alone. Tarr et al. (2017) showed: synchronous dancing significantly increased pain tolerance (an endorphin marker) and feelings of connectedness more than asynchronous dancing.

Do these activities also work digitally?

Only to a limited extent. The endorphin system is primarily activated through physical presence. Only those who are physically present benefit from the biochemical bonding effect. Digital communication can maintain friendships but cannot produce the same neurochemical effect.

How often should you do activities together?

For close friends (the 5-person layer), weekly contact is optimal. The form of contact matters less than its regularity. Even a shared meal or a walk once a week can strengthen the bond — as long as the activity releases endorphins.