Phase Transitions in Biased Opinion Dynamics with 2-choices Rule

Abstract

We consider a model of binary opinion dynamics where one opinion is inherently 'superior' than the other and social agents exhibit a 'bias' towards the superior alternative. Specifically, it is assumed that an agent updates its choice to the superior alternative with probability $\alpha >0$ irrespective of its current opinion and the opinions of the other agents. With probability $1-\alpha$ it adopts the majority opinion among two randomly sampled neighbours and itself. We are interested in the time it takes for the network to converge to a consensus state where all the agents adopt the superior alternative. In a fully connected network of size $n$, we show that irrespective of the initial configuration of the network, the average time to reach consensus scales as $\Theta(n \log n)$ when the bias parameter $\alpha$ is sufficiently high, i.e., $\alpha > \alpha_c$ where $\alpha_c$ is a threshold parameter that is uniquely characterised. When the bias is low, i.e., when $\alpha \in (0,\alpha_c]$, we show that the same rate of convergence can only be achieved if the initial proportion of agents with the superior opinion is above certain threshold $p_c(\alpha)$. If this is not the case, then we show that the network takes $\Omega(\exp(\Theta(n)))$ time on average to reach consensus. Through numerical simulations we observe similar behaviour for other classes of graphs.