When Face Masks Signal Social Identity: Explaining the Deep Face-Mask Divide During the COVID-19 Pandemic

With the COVID-19 pandemic still raging and the vaccination program still rolling out, there continues to be an immediate need for public health officials to better understand the mechanisms behind the deep and perpetual divide over face masks in America. Using a random sample of Americans (N=615), following a pre-registered experimental design and analytic plan, we first demonstrated that mask wearers were not innately more cooperative as individuals than non-mask wearers in the Prisoners’ Dilemma (PD) game when information about their own and the other person’s mask usage was not salient. However, we found strong, revealed preference evidence of in-group favoritism among both mask and non-mask wearers when information about the other partner’s mask usage was known. Holding other things constant, non-mask wearers were 23 percentage points less likely to cooperate than mask wearers when facing a mask-wearing partner, and 26 percentage points more likely to cooperate than mask wearers when facing a non-mask wearing partner. Our analysis suggests social identity effects to be one of the main drivers of people’s decision whether to wear or shun face masks during the pandemic. Policy makers should therefore take social perception of face masks into account when designing not only what public messages to deliver, but also who to deliver these messages.