Can One Shared Interest Start a Friendship? Evidence From a Field Experiment

When meeting someone new, finding one thing in common can make conversation easier. Does similarity actually change how people respond to an initial connection request? One field experiment on Facebook investigated that question using messages that included different amounts of shared information. Its findings are useful, but only if we resist treating an online acceptance click as evidence of a durable real-life friendship.

What the field experiment did

The research, indexed on PubMed as 'Similarity facilitates relationships on social networks: a field experiment on Facebook', contacted users through requests from a stranger. Some requests contained no indicated shared attribute, while others mentioned one or two points of similarity. The dependent variable was whether recipients complied with the friend request. The abstract reports greater acceptance in the similarity conditions than in the no-similarity condition, but no additional benefit from mentioning two rather than one shared item.

What was actually measured

The outcome was compliance with an online request in the studied context. It was not years of mutual friendship, quality of offline conversation or the likelihood of a second meeting in Paris. A field experiment helps test a specific manipulation within its setting; it cannot automatically be generalized to every culture, age group and platform. Nor can it show that the suggested similarity was the deepest part of the participants' identity.

Why one real commonality may be enough

People often search for an elaborate self-introduction: job, languages, favorite music, hometown and travel history. But a single relevant shared interest can create an immediate topic. At a museum visit, 'I'm trying to learn more about photography' may be more effective than a long biography. At a running group, a shared goal of getting back into exercise can be enough to start talking. The point is not to manufacture similarity; it is to make truthful common ground visible.

Be careful with manufactured overlap

If an app or event host claims that strangers are compatible because both selected 'food' from a list, the commonality may be trivial. Shared labels can make a greeting easier without predicting values, trust or long-term mutual interest. Two people may love cinema but want different social lives. The experiment's results do not establish an algorithm for friendship matching. Common ground is an invitation to explore, not a guarantee of compatibility.

Try a concrete question rather than a résumé

Use the setting to ask something with room for an individual answer: 'How did you get into this?', 'Have you tried this class before?' or 'Which part of the exhibition did you like?' Listen and follow the response. If you discover a real shared interest, mention a specific future opportunity: another class, a related film or a short walk. Then let the other person's response determine whether the connection continues.

What repeat encounters add

A point of similarity can open the door, but repeated experience reveals more. You learn how someone follows through, jokes, disagrees and treats others. Friendship develops through mutual choice and time together, not only through identical checkboxes. The responsible conclusion from the field experiment is narrow: perceived similarity influenced an initial online request in the study. The practical possibility is broader but still uncertain: use authentic common interests to begin conversations and let future encounters test the relationship.

Turn common ground into a real interaction

Imagine two people both list photography as an interest. That is a helpful reason to start a conversation, but it is not the conversation itself. One prefers documenting street scenes and the other loves studio portraits; their shared label hides quite different habits. A better first meeting gives them something specific to explore: a short photo walk, an exhibition or a discussion of pictures they have recently taken. That creates fresh evidence of whether being together feels enjoyable.

If the next interaction is pleasant, follow the evidence rather than relying on a profile's similarity score. Suggest a second activity with clear time and place, and accept that a common hobby might remain just a common hobby. The field experiment examined behavior within an online social-network setting, which is meaningfully different from repeated in-person meetings among Paris adults. Similarity can help explain why a contact begins without demonstrating why an enduring friendship forms.

Another way to understand the evidence is to separate three stages: noticing similarity, choosing to interact and deciding to continue. Two people who share an interest may discover an easy first conversation but incompatible schedules, or different preferences around social closeness. Alternatively, people with fewer obvious interests in common may find each other's company engaging. A shared activity provides a context for testing compatibility in real life; it does not predict a relationship with certainty. Resist claims that a high similarity score reveals your future best friend. That would go far beyond what a field experiment or survey can establish.

Sources and verification

Similarity facilitates relationships on social networks: a field experiment

Are You Your Friends’ Friend? — Almaatouq et al. (2016)

References are provided to support the specific research or public context discussed above. Correlation does not establish causation, and no meeting or app can guarantee friendship.