Complex contagion leads to complex dynamics in models coupling behaviour and disease

Social dilemmas of sociality due to beneficial and costly contagion

Levels of sociality in nature vary widely. Some species are solitary; others live in family groups; some form complex multi-family societies. Increased levels of social interaction can allow for the spread of useful innovations and beneficial information, but can also facilitate the spread of harmful contagions, such as infectious diseases. It is natural to assume that these contagion processes shape the evolution of complex social systems, but an explicit account of the dynamics of sociality under selection pressure imposed by contagion remains elusive. We consider a model for the evolution of sociality strategies in the presence of both a beneficial and costly contagion. We study the dynamics of this model at three timescales: using a susceptible-infectious-susceptible (SIS) model to describe contagion spread for given sociality strategies, a replicator equation to study the changing fractions of two different levels of sociality, and an adaptive dynamics approach to study the long-time evolution of the population level of sociality. For a wide range of assumptions about the benefits and costs of infection, we identify a social dilemma: the evolutionarily-stable sociality strategy (ESS) is distinct from the collective optimum—the level of sociality that would be best for all individuals. In particular, the ESS level of social interaction is greater (respectively less) than the social optimum when the good contagion spreads more (respectively less) readily than the bad contagion. Our results shed light on how contagion shapes the evolution of social interaction, but reveals that evolution may not necessarily lead populations to social structures that are good for any or all.

When a luxury brand bursts: Modelling the social media viral effects of negative stereotypes adoption leading to brand hate

In early 2020, the World Health Organization (WHO) developed the term "infodemic" to describe the velocity at which data can be exchanged among people, in a free virtual space where firms have limited control over the information diffusion. In particular, the diffusion of information on social media has analogies with the transmission (contagion) of social phenomena and infectious diseases. The aim of this research is to model the viral effects of a luxury marketing campaign when adopting negative stereotypes to increase the market share in a growing market. The campaign generated 506,127 likes of celebrity endorsers/influencers and 17,984 comments spread worldwide in a relatively short period, producing a "burst". Findings revealed the unexpected social burst occurred with negative consumers' evaluation, which has been amplified becoming dramatically damaging for the brand (brand hate).