The Unwritten Rules of Friendship — 6 Core Rules

Do Friendships Have Rules?

Yes — even if they are written down nowhere. In a comprehensive study, Argyle and Henderson (1984) tested 43 potential friendship ruleson British samples. The rules did not come from theoretical models but from pilot interviews — they were drawn from everyday knowledge.

Of the 43 candidates, 21 were rated as important. But only six met all four validation criteria simultaneously: high endorsement in the overall sample, discrimination between active and ended friendships, attribution as a cause of breakdown, and discrimination between high and low friendship quality.

This means that most rules people spontaneously mention apply to relationships in general — but they do not specifically distinguish between friendship and acquaintanceship. Only six do.

The 6 Scientifically Validated Core Rules

The following six rules passed all four validation criteria. They belong predominantly to the exchange and third-party rule categories.

1. Stand up for a friend when they are not present. Loyalty in absence — not only when the friend is listening.
2. Share good news with your friend. Not just problems — positive news belongs in a friendship too. Sharing successes strengthens the bond.
3. Show emotional support. Demonstrate that you care about your friend’s well-being — not only when asked.
4. Trust and confide in each other. Self-disclosure as a proof of trust — showing that you can be vulnerable.
5. Volunteer help when it is needed. Don’t wait to be asked — help proactively.
6. Make an effort to keep shared time enjoyable. The willingness to invest in the quality of shared time.

What unites these rules is a core principle: reciprocity and emotional investment. More general rules such as “respect privacy” or “don’t criticize publicly” were also strongly endorsed but did not pass all four criteria.

Four Types of Friendship Rules

Argyle and Henderson categorized the 26 tested rules into four functional types. Each type serves a different function across the lifespan of a friendship.

Argyle and Henderson propose a staged model: general rules (coordination and third-party) must be upheld for a friendship to survive at all. When the exchange and intimacy rules are followed in addition, the relationship develops into a high-quality friendship.

Gender Differences in Friendship Rules

Women and men weigh friendship rules differently. Women emphasized intimacy rules significantly more — emotional support, intimate conversations, and expressions of affection are central norms in female friendships.

Men, on the other hand, named excessive teasing and mockingmore often as a reason for ending a friendship — a finding that seems surprising at first but fits the pattern: in male friendships, emotional closeness often develops through shared activities and playful interaction. When that play is taken too far, it strikes at the heart of the relationship.

Age differences were comparatively small and did not reach statistical significance. This suggests that the core rules of friendship remain stable across life stages — what changes is the weighting rather than the content.

When Does Rule-Breaking End a Friendship?

The four rule types respond differently to violations. Third-party rules— public criticism, breaches of confidence, jealousy over other relationships — were most strongly blamed for breakdowns. They concern the social environment and thus the loyalty considered the foundation of every friendship.

Violations of intimacy ruleslower quality but do not necessarily destroy the friendship. In ended friendships, Argyle and Henderson observed a revealing pattern: general rules (coordination, third-party) were still being upheld — friendship-specific rules had already been abandoned. The relationship was formally still present but substantively already empty. More on this in our article on friendships that end through rule-breaking.

Limits of Rule Research

The samples consisted predominantly of British participants from middle educational backgrounds. Whether the same six rules apply in other cultures is only partly explored — a cross-cultural analysis shows that only four rules are truly universal.

Moreover, all data are based on self-reports and retrospective assessments. The study covers only same-sex friendships; whether the same rules apply to cross-sex friendships remains open. And causality cannot be established: it is possible that the cooling of a friendship leads to rule-breaking — rather than the other way around.

Frequently Asked Questions

What rules apply in friendships?

Argyle and Henderson (1984) tested 43 potential rules and identified six that met all four validation criteria: stand up for a friend in their absence, share good news, show emotional support, trust and confide in each other, volunteer help when needed, and make shared time enjoyable.

What are the most important friendship rules?

The most reliable indicators of friendship quality are the exchange rules: offering help, showing emotional support, and sharing success news. They distinguish most strongly between active and ended friendships.

Are there differences between male and female friendships?

Yes. Women emphasize intimacy rules more strongly — emotional support, intimate conversations, expressions of affection. Men named excessive teasing and mocking more often as the reason for ending a friendship. Age differences, by contrast, were small.

What happens when rules are broken?

That depends on the type of rule. Violations of third-party rules (e.g., public criticism, breaches of confidence) most frequently lead to a complete breakdown. Violations of intimacy rules lower the quality but do not necessarily destroy the friendship.