Group polarization in virtual communities: The case of stock message boards

This study examines group polarization, the phenomenon that group members tend to become more extreme in their decisions after group discussions, in the setting of virtual communities, specifically on stock message boards. In this paper, I propose two factors – group size and discussion thread length – to introduce the group polarization theories, social comparison theory (SCT) and persuasive arguments theory (PAT), respectively, to virtual communities. I examined the effects that group size and thread length have on group polarization, which is measured by forum participants’ sentiments. The findings suggest that group size has a significant effect on group polarization. The result of thread length, however, is mixed: the effect of thread length depends on the degree of posting activity on the message board. The analysis and findings echo prior literature, in which SCT and PAT are claimed to serve as two key mechanisms that drive group polarization.published or submitted for publicationis peer reviewe