A generalized linear threshold model for an improved description of the spreading dynamics

TL;DR

This paper introduces a generalized linear threshold (GLT) model that improves the description of spreading dynamics by providing a continuous-time, stochastic framework compatible with simple contagion models, addressing limitations of the traditional LT model.

Contribution

The paper proposes a novel GLT model that offers a mathematically clear, continuous-time approach to complex contagion, compatible with simple contagion models, and efficiently implementable via Gillespie algorithm.

Findings

GLT model underestimates spreading speed of LT model

GLT incorporates randomness and continuous time

GLT seamlessly integrates with SI and SIR models

Abstract

Many spreading processes in our real-life can be considered as a complex contagion, and the linear threshold (LT) model is often applied as a very representative model for this mechanism. Despite its intensive usage, the LT model suffers several limitations in describing the time evolution of the spreading. First, the discrete-time step that captures the speed of the spreading is vaguely defined. Second, the synchronous updating rule makes the nodes infected in batches, which can not take individual differences into account. Finally, the LT model is incompatible with existing models for the simple contagion. Here we consider a generalized linear threshold (GLT) model for the continuous-time stochastic complex contagion process that can be efficiently implemented by the Gillespie algorithm. The time in this model has a clear mathematical definition and the updating order is rigidly defined. We find that the traditional LT model systematically underestimates the spreading speed and the randomness in the spreading sequence order. We also show that the GLT model works seamlessly with the susceptible-infected (SI) or susceptible-infected-recovered (SIR) model. One can easily combine them to model a hybrid spreading process in which simple contagion accumulates the critical mass for the complex contagion that leads to the global cascades. Overall, the GLT model we proposed can be a useful tool to study complex contagion, especially when studying the time evolution of the spreading.