  In this work, we define a class of models to understand the impact of
population size on opinion formation dynamics, a phenomenon usually related to
group conformity. To this end, we introduce a new kinetic model in which the
interaction frequency is weighted by the kinetic density. In the
quasi-invariant regime, this model reduces to a Kaniadakis-Quarati-type
equation with nonlinear drift, originally introduced for the dynamics of bosons
in a spatially homogeneous setting. From the obtained PDE for the evolution of
the opinion density, we determine the regime of parameters for which a critical
mass exists and triggers blow-up of the solution. Therefore, the model is
capable of describing strong conformity phenomena in cases where the total
density of individuals holding a given opinion exceeds a fixed critical size.
In the final part, several numerical experiments demonstrate the features of
the introduced class of models and the related consensus effects.
