Simplicial contagion: proposing a new model for social contagion

Complex networks describe well the connectivity of systems of various nature and have been widely and successfully used as the underlying structure on which the spreading of diseases occurs. When dealing with social contagion phenomena such as opinion formation or the adoption of novelties, though, simple pairwise individual interactions do not provide a satisfactory description.

In a new paper out in Nature Communications, a team of researchers including ISI Foundation Research Leader Giovanni Petri and ISI Senior Researcher Alain Barrat introduces a higher-order model of social contagion in which a social system is represented by a simplicial complex and contagion can occur through interactions in groups of different sizes.

To build a modelling framework, scientists formalise a social group as a simplex and adopt simplicial complexes as the underlying structure of the social system under consideration. They thus propose a new modelling framework, namely a model of “simplicial contagion”, that is able to capture the basic mechanisms and effects of higher-order interactions in social contagion processes.

The new model shows both numerically and analytically that higher-order interactions lead to the emergence of new phenomena, changing the nature of the transition at the epidemic threshold from continuous to discontinuous and leading to the appearance of a bistable region of the parameter space where both healthy and endemic asymptotic states co-exist. These results help explain why critical masses are required to initiate social changes, as recently observed in empirical works.

“Simplicial models of social contagion”, Iacopo Iacopini, Giovanni Petri, Alain Barrat, Vito Latora.  Nature Communications, 6th June 2019