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Queuing and wearing masks are both examples of social norms. Credit: FilippoBacci/ E+/Getty images

Social norms are informal behaviour rules that can foster social coordination. Wearing a mask, and avoiding handshakes to reduce the risk of COVID-19 infections, or using the bike instead of the car to reduce greenhouse emissions, or simply waiting in a queue are examples of social norms that many people adhere to even though they are not written in law. But despite being so important, the way social norms emerge and regulate cooperation among strangers is poorly understood.

Researchers from Italy, Spain and Sweden have studied the link between social norms and collective risk in an online experiment over 30 days. The study involved 286 people, randomly assigned to groups of six individuals that were shuffled daily. Each day, all participants in a group started with 100 ‘credits’ and had to decide how many points to donate to avert a collective risk. When donations reached a predetermined threshold (unknown to the participants, but corresponding to 300 points) the group members could keep the points they had not donated. Otherwise, they risked losing everything.

The actual outcome depended on a sort of manipulated toss coin performed by the researchers: in some experimental rounds players had a 40% probability of keeping their points even when the threshold was not reached; in others, the probability was only 10%. Half of the participants spent the first two weeks of the experiment in the ‘high-risk scenario’ and the other two weeks in the ‘low-risk’ one. The other half had the opposite experience. Participants were interviewed on their expectations about what the others would do before each round, and were also informed about the contribution of their group members. On the last day, participants had one chance to punish another player for being non-cooperative.

In the ‘high-risk’ settings, the average contribution and ability of groups to reach the threshold was higher than in the ‘low-risk’ one, showing that shared social norms had emerged. Participants who first learned those norms under ‘high-risk’ groups tended to slowly abandon them after switching to ‘low-risk’ settings. By those who went from low- to high- risk settings halfway through the experiment quickly increased their average contributions after the change.

“We were able to show how social norms co-evolved with behaviour, and how this co-evolution was affected by the risk of collective disasters” says Aron Szekely of the Collegio Carlo Alberto in Turin, first co-author of the study1, with Francesca Lipari from Universidad Carlos III in Madrid. “We observed that expectations about others’ behaviour is a strikingly strong driver for cooperation,” adds Giulia Andrighetto of the ISTC-CNR Institute of Cognitive Sciences and Technologies in Rome, who led the study. “Believing that others believe that what you’re doing is right is a far more powerful driver than believing that what you’re doing will benefit you”.

According to Maria Carmela Agodi, a professor of sociology at the University of Naples, who was not involved in the study, “the data provided in this study are of great value, thanks to methodological clarity. The study also suggests that policy-makers should take into account expectations, distinguishing between compliance, in which individuals obey without legitimizing the rules, and agreement, which involves legitimization”.