  Models of opinion dynamics play a major role in various disciplines,
including economics, political science, psychology, and social science, as they
provide a framework for analysis and intervention. In spite of the numerous
mathematical models of social learning proposed in the literature, only a few
models have focused on or allow for the possibility of popular extreme beliefs'
formation in a population. This paper closes this gap by introducing the
Partisan Confidence (PC) model inspired by the foundations of the
well-established socio-psychological theory of groupthink. The model hints at
the existence of a tipping point, passing which the opinions of the individuals
within a so-called "social bubble" are exaggerated towards an extreme position,
no matter how the general population is united or divided. The results are also
justified through numerical experiments, which provide new insights into the
evolution of opinions and the groupthink phenomenon.
