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School of Mathematical Sciences

Study identifies how social norms change

Social conventions, such as shaking hands or dressing formally, allow us to coordinate smoothly. But what happens when a new convention replaces an old one? This question is explored in a new study featuring researchers from Queen Mary University of London, City University of London and the University of Barcelona.


The study, published in the journal PNAS, investigated the process of norm change by looking at 2,541 linguistic norm shifts occurring over the last two centuries in English and Spanish.

“We scanned through millions of books digitised by Google and considered such cases as the emergence of the American spelling in the US – such transitions from behaviour to behavior or from analyse to analyze – as well as the gradual selection of one way to do the subjunctive in Spanish, where two equivalent forms exist,” said Roberta Amato, co-author of the study from University of Barcelona.

Three behavioural changes

The authors identified three markedly different behaviours in the data depending on whether the behavioural change results from the action of:

  • A formal institution, such as the Royal Academy for Spanish in Spain (RAE)
  • An informal institution, such as new dictionaries published in the US during the 19th and 20th centuries
  • A spontaneous process occurring in absence of any institution and triggered by a small number of committed users who stubbornly prefer the new convention over the old one

They also proposed a simple mathematical model that reproduces all the empirical observations and confirms the validity of the classification.

Dr Lucas Lacasa from the School of Mathematical Sciences participated in the design of the research, in the data analysis and in writing the paper. He said: "The distinctive behaviours observed share interesting similarities with physical processes. When the norm changed is enforced by a regulation, we found that the process is similar to what happens to certain materials when they are subject to an external magnetic field - jiggling atoms composing the material instantaneously align with the magnetic field and the material gets abruptly magnetised in a top-bottom, orchestrated fashion.

“Conversely, in the case where the norm adoption is spontaneous and unregulated, the process is bottom-up and self-organized: a purely collective phenomenon.”

Better understanding of society

City University of London’s Dr Andrea Baronchelli, who coordinated the study, added: “The implications of the study are broad. Language is a wonderful playground to test theories of norm change thanks to the availability of digitised texts but the mechanisms we identified apply to other domains as well.  

“Multiple parties, from Governments to private organisations, are nowadays trying to influence conventional behaviours and beliefs, and we know that online social networks are speeding up the process of collective behavioural change.

“Understanding how social norms change, and what signatures this change leaves in the data, will lead to a better understanding of our society and help shape interventions aimed at contrasting undesired effects.”

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